And now for a change of pace from serrated tongued terror birds and bonesaw theropods to a new look at Masiakasaurus knopfleri in terms of its lifestyle. This is an idea of mine that I have been kicking around for a while so time to dust it off and present it. It's a bit of a stop-gap until I wade back into talking about ziphodont cutlery.

Masiakaraurus knopfleri credit James St. Johns. CC2.0

When I look at how an extinct animal likely lived I use a blending of three criteria:

1) Is there a reasonable analogue available? or at least a composite analogue?

2) Is the lifestyle feasible with regards to the local ecology/environment this animal likely lived in? i.e. maybe dedicated piscivory is not the best idea in a semi-arid habitat.

3) Are there any substantiating osteological/biomechanical clues in the skeleton? Trace fossils? Gut contents?

So with Masiakasaurus we have an interesting little character. It's actually the most well known noasaurid. In fact it is one of the better known theropods at this point. Now because Masiakasaurus knopfleri is a relatively recent addition to the theropod canon it gives us a good glimpse of how the suggestion of a lifestyle, then becomes repeated, and then becomes unquestioned. It is in fact a picture perfect view of how dogma arises.

used w/permission credit Luis Rey

And for Masiakasaurus the lifestyle that is most heavily repeated is the fishing one. Why is this?

Well first of all let's review why the dental design is so weird in this guy. The anterior end of the jaw is characterized by the procumbent dentition and lack of serrations which grade back into more typical laterally compressed serrated teeth towards the back.  Carrano, Sampson & Forster 2002 interpreted this heterodont pattern as indicative of the animal having the ability to grasp at small prey items which could be further minced in the rear teeth. They muse that "One possibility is that Masiakasaurus was insectivorous or piscivorous, using its anterior teeth for acquiring small, whole prey items and its posterior teeth for maceration."

Evolving from this simple suggestion you can clearly trace the insertion of this view as the dominant one with regards to how Masiakasaurus lived. But given that it has really never been fully tested (although Jaime Headden questioned it) is there any merit to dedicated piscivory in Masiakasaurus?

Is fishing Masiakasaurus really just a knee jerk reaction - "Ughhh it's doing something different with those teeth... ummm.... fish!!"

I am going to endorse theirs and others suggestions that the anterior teeth did indeed seize relatively small, single prey items and the posterior teeth did indeed help slice prey items too big to swallow whole. But I don't think that these prey items were commonly fish - which were likely not that common in semiarid Late Cretaceous Madagascar - but that its most common prey was the various likely fossorial animals it shared its island home with.

I hypothesis it was a fossorial animal hunting specialist.

Is there anything in the skeleton of this animal that could substantiate this claim?

from Carrano et al. 2011

If we start working our way back from the head we can see that the neck, at least for a theropod, is relatively straight. And there is an anatomical reason for this. From Carrano 2002: "The posterior cervical vertebrae of Masiakasaurus lack any elevation of the anterior face over the posterior face, suggesting that the base of the neck was relatively straight. They differ from those of coelophysids in being taller and wider relative to their length, bearing larger epipophyses, and having antero-posteriorily shorter neural spines."

To translate the vertebrae did not form the classic sigmoidal "S" shaped neck of theropods. Masiakasaurus was not optimized to achieve the kind of strike that herons do when fishing. Additionally  the relatively short vertebrae (taller and wider relative to length) is incongruent with the relatively long vertebrae of azdharchids, herons, and Tanystropheus - all likely strikers of small prey.

Quetlzalcoatlus sp. Jaime Headden CC3.0

Tanystropheus longobardicus. CC3.0 credit Ghedoghedo

Great Blue Heron. Ardea herodias

So for three tetrapod lineages that - certainly in the case of the heron but most likely in the other two -strike at small prey with their neck in a downward motion and all of which feature very elongated cervical vertebrae, Masiakasaurus does not line up well with.

Additionally from Carrano et al. 2002: "Like abelisaurids and most other basal theropods (but unlike coelurosaurs), the cervical centra zygapophyseal facets are not "flexed" and exposed anteriorly. The three cervicals from the Late Cretaceous Lameta Group of India ascribed to Laevisuchus indicus (Huene & Matley, 1933) are similar to those of Masiakasaurus in most respects, as is the cervical neural arch of Noasaurus. All three display short, anteriorly-placed neural spines, and postzygapophyses that are swept back strongly posteriorily."

What this means, in my shotgun blast translation, is that all that stuff that stuff that sticks out off the cervical centra - the neural spines, the zygapophyses - it is all swept back to streamline the whole contour of the cervical osteology. Almost as if the animal wanted to have any potential obstructions diminished that would impinge it from sticking its neck into tight spots - like deep into a burrow for instance. Furthermore this adaptation might be congruent in other noasaurids hinting at potential similar function and ecology across this group.

An interesting transition occurs when we move from the cervical vertebrae into the dorsal (i.e. torso) vertebrae. Carrano et al. (2011) take note of the interesting transition in this theropod and that it differs from the pattern in most theropods: "The tenth cervical vertebra (C10) lies at or near the cervicodrosal transition, although this can be difficult to define in theropods. Its unusually long proportions indicate that Masiakasaurus was characterized by antero-posteriorly lengthened centra thoughtout the presacral vertebra column. This is unlike the condition in most theropods, where the cervicodorsal transition is marked by one or two anteroposteriorly short vertebrae."

Masiakasaurus is breaking all the rules... but why?

Gone are the short vertebrae of the cervical region instead (from Carrano et al. 2002): "They are spool shaped, weakly amphicoelus, and lack foramina. Unlike the dorsals of Majungatholus, the centra are not shortened but remain anteroposteriorly elongate (approximately twice as long as either as either wide or tall), as in most coelophysids, smaller theropods, and Elaphrosaurus."

When vertebrae are amphicoelus that means both surfaces of a vertebrae are concave and there is good potential for mobility in several directions. This feature, combined with the relatively longer vertebrae, speak to a relatively mobile trunk region. Which is an interesting contrast to the relatively stiffer neck region. Its almost as if the animal needs the ability for its trunk to squeeze and squirm around in tight places - like into a burrow.


So if the anterior of the body is, as I am suggesting built to get into tight spaces i.e. burrows we should also expect to see some interesting adaptations in the pectoral girdle.

From Carrano et al. 2011: "The scapula and coracoid show an unusual morphology that finds some complacement among other members of Ceratosauria. When articulated, the scapulocoracoid is mediolaterally curved and presents an enormous area for muscle attachment anterior and ventral to the glenoid."


So we have some buffed arms... potentially for digging maybe? However despite the indication of a robust pectoral girdle the morphological theme of trying to "streamline" the bauplan - which I argue is to better access burrows - is persistent.

From Carrano et al. 2011:

"The scapula has a curved blade that reflects the shape of the underlying rib cage, and is broad relative to its length as in coelophysoids as well as other ceratoraurs."

Tranlation: the shoulder blade closely hugs to and mimics the contour of the rib cage. The ecological inference I argue is to diminish obstacles when pummeling into burrows.

"The glenoid has a pronounced anterodorsal rim, as in Ceratosaurus and Majungasarus. In posterior view the scapular portion of the glenoid is D-shaped, and substantially taller dorsoventrally than wide mediolaterally. Its ventral margin along the coracoid suture is oriented obliquely rather than horizontally."

Again the glenoid, or shoulder socket, is showing adaptations to diminish lateral projections and make the anterior of the animals body as flush and streamlined as possible. All useful traits to facilitate entry into tight spaces i.e. burrows.

from Carrano et al. 2011

From Carrano et al. 2011:

"The coracoid is expansive and oval, with long axis oriented anteroposteriorly (fig 18a above). It is much broader than the same element in basal theropods such as Dilophosaurus and Coelophysis, more closely resembling the condition in Elaphrosaurus. Limusaruus, and abelisaurids (although it is more anteroposteriorly elongate than in the latter). The posteroventral process is blunt, projecting only slightly beyond the posteriormost part of the glenoid. It is extremely thin mediolaterally, more so than in almost any other theropod, and lacks the characteristic medial concavity."

Did you pick up on that? The corarcoid, though large, is orientated in a front to back direction but the authors note that it is relatively more elongate than other ceratosaurs. The posteroventral process - a process implies a ridge of bone - is blunt. Not only is it blunted it it is extremely shallow mediolaterally, which means it is thin going from the midline of the body out away from the body - more so than any other theropod the authors mention. Both the bluntness and thiness speak to further diminishing any lateral projection that might diminish fitting the anterior of the body into tight spaces.

Let's look at the humerus now (from Carrono et al 2011):

"Overall it is concave curved medially but nearly straight in the anteroposterior plane. The deltapectoral crest is proportionally short, extending down only about one-third of the total shaft length. The distal condyles, although slightly damaged, are clearly flattened proximodistally as in abelisauruds, Ceratosaurus and Elaphrosaurus. Both the entepicondyle and ectepicondyle are located along the narrow margins close to the distal end, but are indistinctly developed in this specimen."

credit Carrano et al. 2011

Now, for our purposes here the most illustrative picture is B, the posterior view - which means you are looking at the humerus from the rear. What you want to notice is that the humerus curves medially- or inwards - from top to bottom. This exquisitely follows the trend that I have been noting all along of lateral projecting bits of anatomy are brought as close in line with the body to precent blocakage into tight spaces. Furthermore the authors note that the condyles - the rugose attachments at the distal end of the humerus - are undeveloped. This feature further streamlines and narrows the anterior aspect of this animal.

But despite these anatomical concessions to diminish lateral projections the pectoral girdle was robust, undiminished and likely very mobile From Carrano et al. 2011:

"No reduction in functionality is evident from the preserved remains. In contrast, the morphology of the humeral head and the expanded muscle origination areas on the ventral pectoral girdle suggest that mobility was significant and perhaps enhanced over the primitive theropod condition."

The morphology of the manual phalanges is interesting - might be useful to compare their morphology with the phalanges of animals that dig....

credit Carrano et al. 2011

Looking at the manual unguals we see they are relatively short and mediolaterally compressed. They do look a little blunt to be optimized for seizing prey. Could be indicative of some capability in digging.

credit Carrano et al. 2002

Moving towards the pelvic area this trend continues.

On the pubic boot (Carranno et al. 2002):

"The distal end is enlarged into a relatively small, rounded "boot" that projects posteriorly form the main shaft axis.... In most other theropods the boot is either small, lobular and unremarkable (coelophysisds), enlarged anteroposteriorly (allosauroids), or lacks an inset (most coelurosaurs)."

Admittedly not the most compelling piece of evidence so far but it is interesting to note the divergence from other theropods and that the "boot" projects posteriorly - again to diminish bony protuberances that might block passage into burrows.

credit Carrano et al. 2002

Looking at the femur Carrano et al note:

"The femoral shaft is bowed strongly anteriorly and more subtly medially (fig 14)."

credit Carrano et al. 2002

This medial bowing is best seen in B - looking at the femur posteriorly (from the rear). It is quite evident that it bows medially and this feature is consistent with the trend I have been noting of potential laterally projecting bony features being brought close to the body medially. All of which is consistent with a body plan designed to exploit fossorial creatures.




Does this suggested lifestyle make sense within the paleoecology of where it lived? I must state that here things get a little equivocal as pinpointing true fossorial adaptations in the presumed prey base that I suggest Masiakasaurus exploited is currently lacking.

While evidence of dedicated fossorial specialists that lived with Masiakasaurus is equivocal (but that may change) there are a lot of promising candidates. These are animals that - even if they don't actively burrow themselves - they certainly fall within a size range of animals that frequently use other animals burrows, abandoned or otherwise. Especially in hot arid land with various terrestrial crocs and predatory theropods on the surface.

Simosuchus clarki, the pug nosed notosuchian. credit Gordon E. Robertson CC3.0

Vintana sertichi credit Lucille Betti-Nash (c)

Beelzebufo ampinga. credit Nobu Tamura(spinops.blogspot.com)  CC3.0

Araripesuchus patagonicus. remains of the same genus have been recovered from Madagascar. credit Gabriel Lio. CC3.0

A diverse fauna of snakes also inhabited Madagascar in the Late Cretaceous. Madstoia madagascariensis is the largest at close to 8 meters and, although no skull is known, was likely a macrophagous predator. Kalyophis, which shows some weakly developed aquatic adaptations.  Menarana, which has been suggested to be fossorial. There is a paper online here if you want to read up on them.

Again I am not going to get into the nitty-gritty of were these guys really fossorial. Chances are in a hot arid climate, with predatory crocs and theropods roaming about, and at their size range they likely were. It is certainly a more tenable and viable food base than fish for which I can find no reference to in the Maeverano formation. Furthermore I am not excluding fish (or scavenging, insectivory) as part of their diet. Indeed exploitation of lungfish coiled up in their burrows during the dry season is a very viable option.

Canis simensis. credit Harri J. CC2.0

And finally I propose Masiakasaurus most analogous to: the Ethiopian Wolf (Canis simensis). This canid of the Ethiopian highlands primarily hunts burrowing rodents - especially big-headed mole rats. And it has specialization in its jaw indicative of this lifestyle with an elongated head, long jaw, widely spaced and slightly procumbent dentition.

Ethiopian Wolf. credti Paul Gervais

credit Jaime A. Headden The Strange Case of Dr. Masiaka & Mr. Vicious CC3.0

Duane Nash

Ethiopian Wolf credit Rod Waddington (lolz) CC2.0

So to wrap it up:

The unique and compelling skeletal morphology including; relatively straight neck due to short vertebrae; unique transition to long, flexible dorsal vertebrae from short, stiff neck vertebrae at cervical/dorsal juncture; streamlining of vertebral processes, pectoral and pelvic girdles; potential adaptations for digging in manual unguals/phalanges, mobile pectoral girdle & muscle attachments; medial bowing in of femur & humerus; and long noted procumbent dentition.

A possible diverse and abundant fossorial prey base.

A likely viable and useful modern analogy in the form of the Ethiopian wolf.

All speak to a tenable interpretation of Masiakasaurus knopfleri as a fossorial animal hunting specialist.

Further analysis and discovery of other noasaurid material may show similar adaptations potentially illuminating a Gondwanan radiation of fossorial hunting specialist. Fossorial notosuchians and mammals diversifying at the time may have fostered these specializations.


Can you dig it?



special thanks to Andrea Cau for providing pdfs of papers

Papers

Carrano, Mathew T., Loewen, Mark A., & Sertich, Joseph J.W. (2011) New materials of Masiakasaurus knopfleri, Sampson, Carrano, and Forster. 2001 and implications for the morphology of the noasauridae (theropoda: ceratosauria). Smithsonia Contributions to Paleobiology number 95

Carrano, Mathew T., Sampson, Scott D., & Forster, Catherine A. (2002) The osteology of Masiakasaurus Knopfleri, a small abelisaurid from the Late Cretaceous of Madagascar. Journal of Vertebrate Paleontology 22(3) Sep 2002 510-534

Sampson, Scott D., Carrano, Mathew T., & Forster, Catherine A. (2001) A bizarre predatory dinosaur from the Late Cretaceous of Madagascar. Nature vol 409. January

Been pretty productive here for a bit... gonna go on hiatus for most of September as I am going on a road trip to the Pacific Northwest. When I unplug I really unplug so I probably will not be responding to comments either. But I plan on hitting the ground running through late September & October with more of the same grande guignol theropod madness... including more bonesaw stuff, theropod death assemblages, theropod socio-ecology, predator-prey ratios, ontogeny, carch, ceratosaur and dromaeosaur stuff further down the pike and... hint - hint, what is tomorrow the anniversary of?

Also I will be at SVP in Dallas spreading my antediluvian tentacles, so if you are a reader make sure you come up and say hi and chat me up!! And talk about bonesaw theropods over some Texas BBQ!!

Well now, it has been a little bit now - such is life. I was honestly surprised that my last post on Masiakasaurus received such positive feedback, no really problems with my interpretation at all, at least from the comments and feedback I received.

There shall be no such good feelings and consensus with these posts as I am wallowing back into the treacherous waters of Spinosaurus once again!!

credit Duane Nash

In these posts I want to lay out my most current ideas, speculations, theories, and thoughts concerning the new Spino as revealed by Ibrahim et. al. a little over a year ago. As such I hope it will serve as an impetus and inspiration for new and hopefully more rigorous research. So I am just going to put it all down here. I do have a standing offer that if any researchers want to publish on an idea or theory that I put forth in this blog simply get in touch with me and list me as a coathor/credit this blog.

My idea posted here that Spinosaurus was not fully bipedal, nor classically quadrupedal either, but is best characterized as a belly slider continues to get a lot of page views. I will embellish my case for that locomotion in these posts as well as some other possible locomotory modes used during the creatures' ontogeny. More importantly I will explore how this creature likely moved in its predominant habitat - the water - which is more important imo than how it moved on land anyways. If you are still holding out that spino was primarily terrestrial and only went into the water sporadically we obviously differ right from the get - go in which case you will probably not be convinced by my arguments here which treat Spinosaurus as primarily aquatic as a given. I have discussed the sail before here but my thoughts on the sail have changed pretty radically - which will also be detailed in these posts.

Anyways, I hope you have as much fun with this post as I had writing it!!

It is now officially October which basically translates here in southern California where I live to asking yourself is it cool enough that I should think twice about putting on shorts and sandals today? Over on the east coast they experience a little bit more of a seasonal bite, with Florida occasionally getting a twinge of frost by winter. What this means for people over there is that they actually have to dress for the seasons. But what this change in seasons means for a particularly interesting marine mammal is a question of life or death.

credit Ahodges7. Florida manatee @ Sea World Orlando CC3.0

The West Indian manatee (Trichechus manatus) is an obligate tropical water marine mammal. Sustained exposure to cold water (below 20 C or 68 F) will cause mortality. It is this sensitivity to cold water and not predators or even boat propellors that is the chief limit to the population of this species. This means that the Florida population - usually referred to as the Florida manatee - which can range as far north as Massachusetts must migrate south before the advent of substantial water cooling. Anthropogenic warm water refugia in certain enclaves of north/central Florida has created unique opportunities for these Florida manatees to remain in waters year round that they normally would have not persisted in.

However the question (unless you already know the answer) in your head should be why are these animals so deathly cold sensitive - shouldn't their blubber layer allow them to survive in cold conditions? The answer to this query is that manatees have only a slight, incipient fat layer. Despite their rotund appearance their blubber quotient is a far cry from the blubbery status of pinnipeds/cetaceans and other cold water tolerant marine mammals. What gives manatees that "fat" appearance is actually a very thick dermis i.e. they are thick skinned.

It could be argued that skin does not get the attention it deserves despite it being the most visible and exposed organ in vertebrates. It is also usually the largest organ. In fact if you ever want to show off your biological knowledge at a social event asking "what is the largest organ in the human body?" (snark, snark) is a good conversation starter because it is in fact skin.

So why do manatees (and, as I will discuss later, other aquatic tetratpods) develop such a thickened dermis? Manatees don't engage in combative behavior nor do they suffer from intensive predatory pressure. The reason for the dense and thick dermis is related to buoyancy control. While dense heavy bones (pachyostosis) have long been recognized as aides in achieving negative buoyancy in water what is less recognized is that a heavy, dense dermis is also an adaptation for achieving negative buoyancy.

In fact a paper (Kipps et. al., 2002) addresses this very issue. Titled Skin density and its influence on  buoyancy in the manatee (Tricheus manatus latirostrus), harbor porpoise (Phocoena phocoena), and bottlenose dolphin (Tursiops truncatus) this paper compares and contrasts the relative level of skin density as an adaptation to buoyancy control in these three mammals. In both the harbor porpoise and bottlenose dolphin skin density was less than sea water density and contributed a net positive buoyancy force. Thinking in terms of where these animals live - relatively deep water - this makes sense to be a little bit lighter than water so they are not always expending energy to stay afloat. However the manatee is notably different in terms of buoyancy. Its thickened dermis provides a net negative buoyancy to its body.

From the study:



What should be restated is that the skin of the manatee:

"equaled 70% of the negative bouyant force of their dense, pachyosteosclerotic ribs."

That is substantial. Also of interest is that the manatee's buoyancy changes with water depth - which is a known phenomena in diving marine animals:

"The manatee is positively buoyant at the surface and negatively buoyant at depths of less than 10 m."

Now think about this in terms of what and where a manatee is going to be living and foraging. When they are just resting, breathing, or just lolly-gagging about at the surface it makes sense for them to be just slightly buoyant at the surface. However since they are herbivorous and much of their food will be foraged below the surface of the water it also makes sense that once they dip below the surface they are negatively buoyant so that they are not expending loads of energy staying deep. But as manatees are not predatory but herbivorous they are not going to go much beyond the photic zone in terms of foraging which is why that 10 meter mark is so interesting - most of the plant mass will be in the upper, shallower levels where sunlight penetrates.

If you are still a little confused about how the densities of different body tissues can change with water depth maybe this paragraph can help you from the paper:


Additionally it is important to realize that lipid (i.e. fat or blubber) and air filled tissues will compress with increasing pressure i.e. depth. What this means is that in shallow water a blubbery tetrapod can be positively buoyant but with increasing depth both lungs and fat tissue will compress so that the diving animal becomes neutral or even negatively buoyant. As a general pattern the neutral or "gliding" phase of diving tetrapods is both energetically and ecologically optimal similar to basically moving around in a zero gravity environment, essentially outer space.

However in aquatic tetrapods that are at most living in 10's of meters of water as opposed to 100's or 1000's meters of water depth, the pattern of the manatee - dense dermis and dense skeletal system - promises more optimization for that habitat choice. With a dense skeletal and dermal adaptation they do not have to expend energy diving - unlike positively buoyant deep divers which must expend at least some energy to get past the buoyant threshold of depth. Furthermore, since they are only living in water depths measured in the 10's of meters of depth it is not a challenge to push off the bottom or swim a bit to get a gulp of air.

At this point it should be apparent to readers where I am going with this. Spinosaurus, as most likely an inhabitant of estuaries, large river systems, possibly coastlines squarely falls more in the pattern of the manatee as opposed to the dolphins in terms of typical water depths (10's of meters) and therefore skin and skeletal density. Long story short give your Spinosaurus depictions a thick skin - looking at the skin of hippos and manatees is a great reference. And so the artists who speculated on the "Mr. Big"Spinosaurus countenance may have hit it closer to the mark than they even realized.

credit Duane Nash

To embellish my case, that Spinosaurus fits somewhere along this pedigree of dense skin/bone aquatic tetrapods of shallow water are there any other semi-aquatic tetrapods that exhibit a similar pattern of shallow water habitat, dense bone, and dense skin. Turns out there is and the best one to talk about next is the hippopotamus.

The Hippo: Can't Swim and Not Really Fat

Although I can't find any relevant literature on hippo skin it is fairly common knowledge that there skin is exceptionally dense and thick. While such a thick skin is no doubt useful to defend against predators and intraspecific combat I am going to suggest that such a thick dermis evolved in concert with those reasons to help the hippo achieve and maintain negative negative buoyancy.

The series Inside Natures Giants takes a look at hippo anatomy and anatomist Joy Reidenberg has some choice words describing hippos skin (start at about the 11:45 mark).


"That's really thick skin... and very, very tough. It feels almost like elephant skin but a lot, lot thicker. I think that's the toughest skin I ever had to cut."


When, after much effort, she finally gets a plug of skin removed you really get a sense of the thickness. She really makes a point that it is not fat but is all skin. The "fatness" of hippos is due to the thick skin. large stomach, and barrel chested torso. Don't fat shame hippos - they probably have a lower BMI than you do!!

Here is a really interesting photo-essay documenting an intrepid male hippo that got into a pretty dangerous situation moving through some rough coastal surf along the Mozambique coast of South Africa. The young male was observed fighting through strong surf and finally scrambling over sharp rocks for over 2 hours to make it around a point into a calm bay.

credit Angie Gullan, Dolphin Encounters & Research Center. Nat Geo

After the hippo finally made it into the bay it collapsed on the beach in sheer exhaustion.

credit Angie Gullan, Dolphin Encounters & Research Center. Nat Geo

These photos and documentation highlight a seldom discussed fact about the hippo - they can't really, in the truest sense of the word, swim. Try as you might (and I have) you will not find images or video of hippos actively swimming a dog paddle motion or other limb assisted paddling. What they do in the water is best described as an underwater run or trot. They use the bottom substrate to kick and push off the bottom - quite rapidly sometimes - and this allows them the ability to propel upwards for air or glide through the water for extended periods.


Underwater locomotion is the topic for another post and I am getting a little ahead of myself. What should be noted is that the correlation of thick skin and shallow water diving should be noted in both the manatee and the hippo.

Are there other aquatic/semiaquatic tetrapods that might suggest shared anatomical features in congruency with an aquatic habit?

Well, I am glad you asked because yes there are several strong candidates displaying various levels of dedication to a watery lifestyle.

Walrus public domain

The walrus (Odobenus rosmarus) is famously thick skinned and although I can't find any rigorous work in how this skin pertains to its buoyancy there is some suggestive data. Several entries on wikipedia mention large bulls with hides that weight over 1,000 lbs and skin that is 3.9 inches thick around the neck. With regards to diving and buoyancy Inuit hunters are quick to attach seal skin floats to a harpooned walrus as it is said to be negatively buoyant. In order to sleep on the water walrus inflate their pharyngeal sacs in order to remain afloat. In a large study of diving seabirds and pinnipeds walrus were observed to be among the most shallow diving pinnipeds never maxing out at about 80 meters (260 feet). This shallow water diving profile makes sense in terms of their primary diet of clams which are most abundant in shallow shelf waters. Remarkable convergence yet again of thick skin, relatively shallow diving (10's of meters), and pachyeosclerotic rib bones (like the manatee).

Malayan tapir. credit Sepht CC2.5

At the other end of the spectrum of aquatic animals are the tapirs. While tapir's penchant for water is well known we now have video showing tapir running along the bottom of bodies of water like hippos - they can achieve negative buoyancy. Furthermore they are noted for their thick skin. According to the San Diego Zoo tapir fact file tapirs are characterized by "thick, leathery yet supple skin with little hair (the exception being the mountain tapir with thinner skin and thick hair)." I want to draw attention to that last bit about the mountain tapir. If the mountain tapir is the >least< aquatic of the tapirs due to it living in elevation where marshes, large rivers, and lakes will be less common on the landscape then a less thick skin is exactly what should be expected according to the theory linking thick skin with shallow water habits. One of the hallmarks of a theory is that predictions can be made and tested.

Although more rigorous anatomical and behavioral studies are needed I think there is a strong suggestion of a trend in the animals I have listed. As we move from tapir to hippo to walrus to manatee  this should become apparent. Increasing aquatic adaptation in these animals is associated with increasing skeletal density and skin density. At the lower end of the scale would be tapirs and at the other end of the scale walrus and manatee. I suspect Spinosaurus sat somewhere between the hippo and walrus in terms of dedication to the water. Spinosaurus therefore likely had an extremely thick and dense skin. This dermis would have "fattened" the appearance of the animal, offered protection from intraspecific combat, predators, and retaliatory prey (sawfish rostrums for instance). I highly endorse the Mr. Big model for Spinosaurus. And if walrus and hippo can pack on over 1,000 lbs of skin on their frame, Spinosaurus with a much larger frame likely packed on a skin weight measured in the tonnage!!

In my next post I will further look into the way(s) Spinosaurus moved in the water. Can't promise when that will be and I apologize if I do not respond to comments quickly as I will be in Dallas this week... and if you read said abstract list for a certain convention you will note there is a study on spino swimming ability. As a little hint for next post I predict that spino will be shown to be just an ok swimmer - probably less efficient than a croc. But this does not imply that spino did not have other ways of moving rapidly in the water (hippo punting hint, hint) ...


Cheers!!

References

N. Ibrahim, P. Sereno, C. Dal Sasso, S. Maganuco, M. Fabbri, D.M. Martill, S. Zouhri, N. Myhrvold, D.A. Iurino (2014). Semiaquatic adaptations in a giant predatory dinosaur. Science 26 September 11, 2014

Kipps, E.K.,  McLellan, W.A,  Rommel, S.A., & Pabst, D.A. 2002. Skin density and its influence on  buoyancy in the manatee (Tricheus manatus latirostrus), harbor porpoise (Phocoena phocoena), and bottlenose dolphin (Tursiops truncatus). Marine Mammal Science 18(3) 765-778. July 2002

I just did my second pilgrimage to an SVP meeting. While my first attendance in L.A. was basically right next door to me (I live in the county north of L.A.) this one required a little bit more travel prep. Luckily I had saved up enough money from my last job doing data entry at a museum to get my expedia ticket and hotel room done for a reasonable amount and I got the discount rate for the preregistration ticket on the last day of that offer so those savings helped. Of course finances is a constant theme for why people do or do not go to this and other events and the #paleo-economy is a topic I do intend to discuss in the future. Fortunately the next two SVP meetings are in North America (Salt Lake City, Utah & Alberta, Canada) so, especially since I just got a solid job, I aim to make both of those.

First of all Texas. This was actually my first time in Texas and was very impressed by the hospitality and niceness of the people of Dallas. Being a leftist Californian I was a little weary of Texas culture but I have to say I was proven wrong by the all around awesomeness of the people and workers of Dallas. They by and large were much nicer and more real than most Californians. Plus BBQ. I tried to keep my gluttony and bone chomping down to a minimum but I did have several feeding bouts at Sonny's in downtown Dallas. It was an epic bonesaw feast....  when in Rome. I also was very impressed with DART (Dallas Area Rapid Transit) that got me from the airport to downtown and from my hotel room at The Marriot to Hyatt convention center very quickly. At first I was a little stressed that I did not get a room at the Hyatt but in retrospect it worked out splendidly as it was usually only a 15 minute commute via DART and it forced me to get out and see more of Dallas. I talked to several people who stayed at the Hyatt and got the impression that they dumped a lot of money into over-priced hotel food and alcohol and did not get out on the city too much. Also by staying at the Marriot I was a block away from the free Aurora light/art installation public event that Dallas put on. The whole arts district was transformed into cool light shows, art installation, psychedielic animations screened onto the sides of a large building. The whole presentation was an interesting contrast because you felt like you should be at some drug-addled rave or burning man show but it was very much a family event. Plus a cathedral sized Catholic church was outfitted with ambient lights and misty smoke pots to create a chilling and surreal effect when you walked in... and people were still performing mass in the church. It was like some weird Fellini film. Also SVP collaborated with the Perot museum to provide free shuttles and catering to the museum on the first night. I have to say the museum was well done, very engaging, and had an interesting architecture too. I commented to several attendees about the museums namesake Ross Perot (the oil magnate and one time presidential hopefull) and they did not know who I was talking about. Made me feel kind of dated lol!! Let's just say ol' Perot was an outsider 3rd party candidate before it became cool to do so. So, yeah if you were wondering why the museum went so in depth into the science of hyrdocarbon exploitation...

Onto the meeting itself.

One of the highlights of course for any of these types of meeting is getting to rub-shoulders with the noted luminaries so to speak of the field. This event was certainly packed with them. Now at my last meeting I got to chat with James Kirkland, Thomas Holtz, Phil Currie, James Farlow, Julius Csotony, Darren Naish, Jack Horner and several others for this meeting I got to chat with many of these same people but also for this event with; Robert Bakker - who I will admit I did get a wee bit star struck over which I don't usually do anymore; Larry Witmer (pestered him about vulture, allosaur, and phorusrhauchid feeding mechanism); and even Paul Sereno (you could guess what I talked to him about)... they all were very nice and personable. Others who I got to meet, some of whom even came up to me recognizing my name which was a little humbling included Anthony Martin and Andrew Farke. Also it was great to meet facebook friends such as Brian Engh and Stevie Moore in real, face to face circumstances.

The whole mood was very polite and convivial which I have to admit I kind of like that but also don't like it. I like it because at my heart (despite occasional explosions) I myself am pretty mellow and relaxed and really don't like seeing people getting bullied, threatened or intimidated. What I don't like about it is that this ethic - which basically all attendees had to agree upon by going and which was constantly plastered all over the event - becomes a form of tone policing. Tone policing, in my view, is bad for science because it creates a situation where how you say something - potentially with anger, aggression, rage, spite, venom, or just too much passion - becomes more important than what you say. Potentially an emotionally delivered argument - even a correct one - can be shot down because it is delivered in the wrong tone. This is my issue with what I see as a creeping group think that science and scientific debate always has to be delivered in such a nice, formal, polite manner. Let me be careful with this because I can see how what I am saying can be misconstrued. I am not suggesting that openly hostile, mean, personal, vitriolic attacks are the way to go. We, myself included, should always aim to be polite and convivial but lettuce b realz not all people are like that and not all cultures are like that. What I fear is that certain peoples, groups, individuals will be shut out from discussion because they do not play by majority rules. A review of some of the top brass in any fields includes some - how should I put it - real assholes. Sometime assholes do some really brilliant, top shelf stuff. I don't know what the answer to this is. Certainly the majority rule in public events - keep it polite please - has a strong argument. But my critique is more of a warning in general. We should always be on guard from overly tone policing people in science. In science what you say should always trump how you say it.

For the talks I don't want to get into real specifics because I am still confused over the whole press embargo and what can or can't be said ( its a load of phooey if you ask me). What I do want to give are some very broad stroke trends or themes I noted and which should garner interest. As opposed to my last SVP where I made a mad dash from lecture hall to lecture hall in an attempt to get some of everything, this time I really just hung out for the archosaur talks ( and some shark, marine reptile stuff too). I do have to say that the sauropod talks might just have slightly edged out the ornithopod talks and that theropods were third in the dino sweepstakes imo. This might have a bit to do with the fact that the last couple of years have seen some truly stunning theropod reveals at SVP (Spino, Deinocheirus) so the bar was a little high. A running theme in several of the talks was that ontogenetic change is a dangerous pitfall in evaluating characters in cladistic analysis. Heterochrony also provides a challenging aspect towards cladistic analysis. the most succinct example I recall is the talk on the dwarf island sauropod Europasaurus by Schmitt A., Knoll F., & Tschopp E. (I don't know who actually gave the talk but probably Schmitt). The interesting thing here is that neural anatomy - the brain - was highly brachiosaurian but the body itself was signaling more basal - closer to something like Camarasaurus. Because it was dwarfed paedomorphic processes gave it more of a basal macronarian gestalt - very cool!! These and other examples of the pitfalls of cladistics also, at least in my mind, suggest that cladistics is every bit as contentious and prone to pitfalls as what I like to concentrate on - lifestyle & ecological reconstruction. I think that there is a general opinion that of the two - cladistics & lifestyle interpretation - that cladistics is the more rigorous, methodological, "hard science" venture but life-style reconstruction is the softer science more prone to baseless speculation, faults of bias, assumptions etc etc. However several of the talks I attended suggested that the dichotomy between the two might not be so sharp. Another theme, especially of the sauropod talks was freaking cute baby/ en ovo stuff (would make a good t-shirt or SVP artwork logo). I was joking with Stevie Moore that I wanted to ask several of the presenters of such topics after their talk who would win in a fight a baby titanosaur or a baby diplodocid as a little poke at carnivora forums/battle royale culture...

Speaking of the question section after the speeches - I think that they should just get rid of the option. Either get rid of the option for questions or give the speeches a five minute intermission for more questions also a chance for people to move between talks. The thing is that more often than not there was no time for questions etc etc. Additionally if you are not among the one or two people that have the luck of getting called on for a question it becomes challenging sometimes to keep track of where the talker goes to if you want to pin him/her down for more detailed discussion. Plus you end up feeling like a stalker... Here is what I suggest. Get rid of the whole question format. Give speakers the full 15 minutes for the talk. Require that speakers - at the end of the speaking session that they are a part of - convene in some predetermined room, or even the same room, to take questions after the symposium (this would allow the speaker & attendee to see the whole syposium). This could be 1/2 to 1 hour where they are mandated to be present to solicit questions from the attendees. This is less time than the poster presenters are required to be adjacent to their poster and I do not think it draconian to hold the speakers to the same standards of making themselves available to questions that the poster presenters have to abide by. Going back to the timing of the talks I also think it useful to have a bit of a buffer time between talks to give people a chance to move from different rooms. I know that it is accepted that people will be moving about but I can only imagine as a talker it be disconcerting seeing people moving in and out during your talk and as an attendee I can't help but feel rude. I hope I don't come off like SVP do a horrible job planning these things - they don't -and it must be a mountain of work to coordinate. At the same time any organization can always look for ways to improve and providing more of a forum for open questions and discussion opportunities can only be a good thing.

I don't have anything that immediately comes to mind to discuss regarding the posters... there was a lot of them, they covered a lot of topics, and the poster presenters were very good and gladly answered questions. Especially impressed by all the poster presenters from Europe, South America, and Asia - did not notice a lot from Africa/Australia. That's a big trip and kudos to you from investing to come to all the way!!

One aspect that I really did enjoy regarding the talks was the way several of the talks really built into and embellished the whole symposium creating a nice little forward momentum. But speaking of momentum I wish there was a mid-afternoon coffee break...

Anyways that was my broad stroke analysis. I hope I don't come off too critical - after all if I didn't like it why would I keep going? - but any venture can find ways to improve.

#2015SVP

Well now... a lot has transpired since my last post in which I suggested that Spinosaurus likely fit within a range of aquatic and semiaquatic tetrapods in having a very thickened skin to aide in ballast. I went to to SVP in Dallas where Paul Sereno discussed his findings on Spinosaurus' swim speed and likely neutral buoyancy in the water. Let's say that his findings - preliminary as they are and no doubt controversy will ensue upon publication - did nothing but bolster my contentions regarding how Spino sat, moved, and generally behaved as a physical body in the water. Based on Sereno's preliminary findings ol' Spino was just an ok swimmer at about 3 meters/second. That is just a tad bit faster than Michael Phelps but quite a bit slower than your average croc. Keep in mind that crocodiles for the most part are not actively chasing and pursuing fish in the water column like an otter or seal but are more often than not using sit & wait tactics. stalking, and using physical obstacles to corral fish. So the notion that Spino was actively paddling and dashing after fish in open water may not make much sense. That is not to say that Spino didn't have a way to actively pursue fish (underwater running hint, hint) but that will have to be a future post. Also - based on Sereno's preliminary findings - Spino sat low in the water in terms of buoyancy. In fact as I have been saying since the week the Ibrahim new look Spino was unveiled the WHOLE DARN SAIL WAS UNDERWATER when Spino was in deep water!! So I gots to feelz myself a bit here - told ya so, told ya so, told ya so. This really puts a damper on the prevailing notion, that in my opinion, has just kinda been accepted and not really questioned rigorously - that the primary use for the sail on Spinosaurus' back was for social signalling. Additionally keep in mind that Sereno's work on buoyancy - and I talked to him at SVP - does not infer that Spino likely had a thickened epidermis that further added density - his calculations were just using the bones. What I am trying to say is that Spino potentially sat a lot lower - like literally right on the bottom - in the water column. What this suggests is that some of the most startling and amazing artwork that came out with the Ibrahim reveal such as this piece by Davide Bonnadonna (used w/permission) might already be dated.

credit Davide Bonnadonna (c) used w/permission

Instead a more likely image for Spinosaurus I would argue is the one below (used w/permission)- created by Christopher DiPiazza of the blog Prehistoric Beast of the Week.

credit Christopher DiPiazza used w/permission

Now I have to hand it to Christopher for being very prescient in doubting the ability of Spino as a swimmer but inferring it instead as an underwater runner and being one of the first artists to depict it as such. The only knock I can give it is that the skin should be a tad thicker (as discussed in my last post) and overall morphology more rotund ala hippo...

And here is my version of the underwater running Spino which is a bit of teaser for an upcoming post on underwater running... (yes, yes I wanted to do just 2-3 posts on Spino but it keeps growing)

Underwater Running Spino "glowstick" (c) Duane Nash use w/permission

So now that that stuff is out of the way (again the sail & underwater running will be future posts) I want to get to what this post is really about and that is two separate topics that might at first appear mutually exclusive but I will link them together at the end of the post: the Evers et al. paper that has spurred on some interesting thought but also loads of misinterpretation on the "popular" front; and, stimulated by discussions provided by LeeB from my last post, the interesting topic of island hopping hippos.

I have waited a bit to really address the Evers paper and, to be perfectly honest, I did this because the paper is just too darn long!! Seriously if the Ibrahim et al. paper got knocks for being overly abbreviated this paper deserves to get some critique on being overly verbose and less than easy to follow as a document. I really doubt most of the people heralding it as the savior of the long-legged Spinosaurus have even read it.

It did not have to be this way as the primary take home message is that Sigilmassasaurus brevicollis is its own beast!! That is about it when it is all said and done. Keep in mind that for Sigilmassasaurus we are talking about vertebrae - no appendicular elements, no skull material, not even a rib. It should also be added that Spinosaurus maroccanus (vertebrae & premaxilary material) is now - according to this study - sunk into Sigilmassasaurus brevicollis. As you may recall the Ibrahim et al. study cleaned house on all North African spinosaurid material and just lumped it all into S. aegyptiacus. The Evers paper could have been much more effective if they just presented their character analysis of the vertebrae, made their arguments for what bones they represent in the vertebral series, and made a succinct and clean argument for North Africa hosting at least two spinosaurids in the Kem-Kem and Bahariya respectively.

This beefy 100 page paper can best be summarized with this paragraph here:



This paper should have just focused on retrieving S. brevicollis as a unique species and not have - I don't know how else to put it - used its bully pulpit to cast doubt on the unique morphology of Spino B and FSAK-11888 - especially since the monograph of the latter is not even published and we don't even have the former anymore. Instead, among other critiques of Ibrahim et al., the authors question the synonymy of Stromer's spinosaur material with Ibrahim et al's. FSAK-11888 and reject their claim of a neotype.

They also insist on describing the retrieval of FSAK-11888 as coming from an "allegedly" associated partial skeleton several times. Understandably this is because the monograph is not yet prepared addressing the taphonomy and collection of said specimen. At the same time Evers et al. seem to really run with this "chimeric" interpretation of FSAK-11888 casting doubt on its validity. Is it chimeric due to Moroccan fossil dealers pulling together disparate skeletal elements in order to make a sell? If this is the case then why give the animal diminutive pelvic elements? Andrea Cau has addressed this problem on his blog here. The second possibility is that the elements are chimeric not due to anthropogenic forces but due to taphonomic forces, a possibility the authors raise citing several studies alluding to the Kem-Kem having a notorious reputation for mixed elements. However let us reason this scenario out. In both Stromer's Spino B and the Ibrahim FSAK-11888 we have diminutive pelvic elements associated with lengthened dorsal vertebrae, and neural spines... what are the chances of that happening twice with either taphonomic or anthropogenic interventions? Again these critiques are not new, they should be addressed, but I think that they really obfuscate the prime - and very interesting - point of the Ever's paper: that is North Africa hosted two Cenomanian spinosaurids.

Evers et al. also fail to mention a very important layer of evidence in favor of FSAK-11888 representing a single individual. This line of evidence bears repeating - in fact it should have got trumpeted from the hill top loudly a long time ago - and that is that the vertebral and appendicular bone histology of FSAK-11888 both signal a relatively young, sub-adult ontogenetic age . Yup both the diminutive pelvic elements and vertebral column/ribs/gastralia suggest an immature individual. This is not what we should expect if the elements are chimeric. Let's review that bit from the supplemental materials section of Ibrahim et al.:

"Neurocentral sutures preserved in the vertebrae do not exhibit coocssification, nor is there coossification between sacral centra or between the ilium and sacral vertebrae." (pp.13 supp.)

"Two long bones (femur, fibula), a possible gatralium and the proximal end of a dorsal rib were selected for histological thin sections.... (pp. 13 supp.)

"An external fundamental system is not found in any of the four bones sectioned, and vascularization is still prsent in the circumferential layer. We infer a subadult ontogenetic stage for the neotype specimen. This interpretation is also based on the high amount of Haversian systems in the inner cortex, the decrease in density of vascularization towards the surface of the cross section and the decrease in spacing between LAGS toward the outer cortex. Maximum adult size would likely have entailed many years of subsequent growth." (pp. 14 supp.)

Not addressing these histological lines of evidence in the Evers et al. paper is a major omission in my view. As I have said before this paper should have just dealt with Sigilmassasaurus as a unique taxa and by going after Ibrahim et al. in totality in a none too circumspect way they really do themselves a disservice. If you are going to make critiques you can't just omit the stuff that you don't like i.e. the very pertinent bone histology congruency between vertebral and appendicular elements suggesting just one individual. Especially if your paper is 100+ pages long. But Evers et al. are not solely too blame on this front. If you go back and review the several very storied and infamous online critiques of Ibrahim et al. including - Switek's, Headden's, Hartman's, and Witton's - you will see that all four of them fail to mention the bone histology data suggesting FSAK-11888 is one, subadult individual. For all of these very vocal and visible blog postings not to mention this line of evidence is very interesting. Make of that what you will.

The unfortunate effect of this paper is that it adds fuel to the fire for those in the "popular realm" (i.e. JP3 Spino fanboys) who are hellbent on retrieving an upright bipedal Spinosaurus at any cost. "Look at this 100 page paper in PeerJ - the authors shoot down the Ibrahim paper!! Whoopee long legged Spino lives again!!"

Again, while the new paper might be correct in there being two or more spinosaurids in N. Africa (maybe even a species complex of Spinosaurus?) and that their critique of Ibrahim et al. lumping all N. African spino material into S. aegyptiacus may be valid- the morphology for Spinosaurus that the Ibrahim et al. paper gave did not hinge on the Sigilmassasaurus or S. maroccanus material anyways (which is mainly isolated vertebrae). We still, at the end of the day have the congruence of morphology in Spino B and FSAK-11888 standing tall (pun intended). 

The authors even begrudgingly concede this in the last sentence below:



Furthermore, on a wider note, this movement to retrieve a long-legged, bipedally striding Spinosaurus (Hartman's skeletal is usually the one bandied about - but not a fan of it myself or his spinosaurids in general - too gracile imo) both on the popular and scientific front I predict will fall flat on its face eventually (pun intended). Two specimens - as controversial and questionable as they may be - both displaying similar gross morphology in the pelvic area > zero specimens of Spinosaurus showcasing "normal" sized theropod pelvic anatomy. One set, the one we do still have, shows ontogenetic congruence between the vertebral and appendicular elements i.e. not likely a chimera. That's right, there is exactly 0.0% verifiable evidence for a long-limbed, classically bipedal Spinosaurus or even spinosaurid in North Africa. None. Any assertions for this interpretation over something more in the Ibrahim et al. ballpark of gross morphology - without skeletal evidence - is an assertion of a mythical creature over something we do have (controversial as it is) evidence for. It's high time we flip the script on long-legged Spinosaurus being the de facto representation - there is no evidence for that animal at all.

Now with no clever segue at all (although I promise it will relate back to above discusssions) I want to go into into island hopping hippos.

What really started this off was me stating - as others notably the San Diego Zoo - that hippos can't, in the truest sense of the word, actually swim. They are denser than water and don't really have large flippered limbs that can grab and push back large volumes of water. The reason for their density is - and I will go into this more in depth in a future post - that their primary mode of locomotion is best achieved via their ability to stay low in the water column. Hippos use a foot propelled running/trotting locomotion "underwater punting" in which the foot pushes off the substrate to achieve long and slow gliding phases or when hippos want to move faster they actually take shorter and quicker steps. At first this might seem counter intuitive but try it yourself. Go into a body of water at least 2/3 up your chest. Now experiment with running underwater to achieve maximum velocity. You will quickly realize that short/rapid punting steps outpaces long, gliding paces. Therefore for hippos to take advantage of moving quickly in the water via short/punting steps they need to be substantially denser than the water or else gliding phases (which are slower) will take over due to relatively increased buoyancy.

Before we take a look at the various island hopping hippos and other lines of evidence that are cited in favor of hippos being able to swim let's take a closer look at an animal that I neglected to mention in my  last post but offers much utility to discuss here - the pygmy hippo (Choeriopsis liberiensis).

Pygmy hippo. public domain. Mt Kenya Wildlife park

The pygmy hippo is a startling contrast to its larger more celebrated cousin. Although of the same family they are not closely related being of different genera and perhaps diverging as long ago as 8 million years ago (Boisserie, 2005). Pygmy hippos are very much smaller, more reclusive, and less aggressive or boisterous than their larger relatives. Their range is very limited: this is likely, I muse, because of the general loss of dense forested habitat in Africa since the Pleistocene that is their preferred habitat. Which brings me to my next point - pygmy hippos are very much forest animals, another contrast between their more grassland/savanna loving larger counterparts. In fact the animal most often posited as ecologically analogous to the pygmy hippo is the tapir.

Let that last bit about the tapir analogue sink in a bit - as you should recall in my last post I suggested tapir provide a good proxy for an animal that is not yet quite as aquatic adapted as a hippo. Tapirs can underwater punt, they have thickened skin that likely aides as ballast, and a barrel shaped torso for underwater streamlining. They are likely more bouyant than a hippo and might be able to achieve a swimming stroke or even float in saltwater. To put it another way tapirs are just getting their feet wet in terms of dedication to an aquatic existence. All of this is less than rigorous but is worthy of more testing mind you...

Going further if we take this analogy to tapirs for pygmy hippos and the general observation that they appear less massive skeletally , have less skin, and can potentially float or even actively swim - then maybe pygmy hippos actually did colonize offshore islands via swimming/floating. This may have especially been the case when pygmy hippos had a more wider distribution in the past.

When I took the question of pygmy hippos actually being able to swim into my laboratory (i.e. youtube clips) I very quickly - within the first 2 or 3 videos - saw some behavior suggestive of swimming. Mind you I am yet to see any good footage of big hippos swimming in any form...

infant pygmy hippo swimming a little

Follow this link here to see some pretty good footage of a newborn pygmy hippo calf doing some ok swimming. It does appear to achieve limb assisted swimming in several instances in this clip. You will also notice that as soon as it stops moving its limbs it sinks like a stone. I know young hippos of the big species have been suggested to be a little more bouyant than their parents but am not quite sold and them being able to self propel across 10's or 100's of kilometers of open ocean. I am a bit skeptical of them having the strength and stamina to pull off such feats. But then again maybe saltwater provides just enough buoyancy to overcome their densisty...

Here is another youtube clip of an infant pygmy hippo that appears to get a little bit of limb assisted swimming going on... but as soon as it stops pumping those legs it sinks like a stone.


For comparison here is an endearingly cute video of an infant hippo (H. amphibius, larger species) moving in water. It always appears to sink like a stone after pushing off the bottom. There is one sequence towards the end where it looks like it is trying to paddle but doesn't really get anywhere.


Malagasy Hippos

Choreopsis madagascariensis w/ H. amphibius skull. public domain 1923

Now, I will concede that pygmy hippos show a little bit more promise for swimming or floating across deep saltwater bodies than their larger cousins which leads me to my next point. The famed Malagasy dwarf hippo - which represents several species of hippo that only recently went extinct on Madagascar -  may actually potentially be part of the same genus as the pygmy hippo. I am not going to pretend to be an overnight expert on Malagasy hippo taxonomy but let's just say that it is unresolved and that the putative ancestor(s) of the various - highly terrestrial or even mountainous - recently extinct hippos of Madagascar might have been quite a bit removed from the classic hippo (H. amphibius) we all know and love. Alternatively H. lemeriei is often compared to H. amphibius so it is possible that both genera of hippos made it to the island. So until the taxonomy of the species of hippos that were endemic to Madagascar - some of which may have been a lot closer to pygmy hippos than regular hippos - is sorted out (great grad student project btw) I can't really accept positing the existence of various hippo species on Madagascar as proof positive that hippos similar to modern H. amphibeus actually swam or floated there - but rafting is my favored scenario in any case.   However as I conceded earlier I do hold more hope for dwarf hippos to actually swim or float in saltwater than H. amphibeus.


The Hippos of Center Island, Lake Turkana

Lake Turkana. CC3.0

I have to admit that this one was pretty interesting and a little perplexing. How did hippos colonize Center Island in the middle of Lake Turkana which is the largest desert lake in the world? Investigating this did get me to finger through my old copy of Eyelids of Morning: The Intermingled Destinies of Crocodile and Man which I always wanted to blog about. It's a great book btw and I don't see books like it really written anymore - pick it up. Back then Lake Turkana was called Lake Rudolph and in the book there are several mentions of hippo in the lake and violent confrontations with the locals. Its an eerie place for hippos because it is a true volcanic desert and testimony to the adaptability of these animals as long as they have water.

Lake Turkana is the largest of the eastern rift valley lakes. It is also a relatively recent lake in terms of origin - 200,000 years old is the most commonly cited age. And research suggests that what we see today - the largest desert lake in the world - might have been in fact two or more smaller lakes and dried up completely as recently as 7,500 years ago. Follow this link if you want a good overview of the complex and dynamic geological history of this lake Paleogeography of Lake Turkana. Even before "Mega-Lake Turkana" nearly dried up 7,500 years ago the Lake Turkana basin hosted several ghost lakes and rivers. Long story short we have a more parsimonious solution to why there are hippos on Center Island.  They need not have swam, floated or rafted there - they most likely were always there - a hold out from when the lake level was a lot lower as has happened several times in the lakes geologic history. Which might happen again as the main incoming tributary for the lake - Omo river - is set to be dammed.

Mediterranean Isle Hippos

composite mounted skeleton H. minor. George Lyras 3.0

Shaking my head on this one.... the problem as I see it is the taxonomy of these beasts is a mess. Yes, we have definite "dwarf" island hippos on Crete, Malta, Sicily & Cyprus. But what can definitely be said about the hippo(s) that they evolved from? Most of the literature I see linked to these animals dates to the early 19th century or even 18th century. They need a revision for sure!!

Compounding the issue is that not only do we have fuzziness on the ancestry of these beasts is that the geological history of the Mediterranean basin is horribly complex. Events like the Messinian salinity crisis of the Miocene in which the whole basin literally dried up could have allowed the ancestor(s) of the Mediterranean "dwarf" hippos to literally walk up to the various isles. High evaporation rates in the Mediterranean also may have provided just the amount of buoyancy needed to float a putative ancestral hippo type beast - especially if not built as heavily as modern H. amphibius and possibly more along the lines of Archaeopotamus.

What can be said about the Mediterranean isle hippos species for sure? From what I gather not much definitely. We can't be precise in terms of who they evolved from or when they evolved? Are they really dwarfed? Do they represent a more ancestral stock of hippo and just evolved in convergence to look superficially like modern hippos? What can be said definitely in terms of their biogeographic origin? Not much really only that they got on those islands somehow.

My final thoughts on the debate of island hopping hippos is somewhere between Mazza (2015) and Van der Geer (2015). If you follow the links at the end of the post you can read their interesting exchange. Neither paper addresses the geological history of Lake Turkana which suggests that the hippos that live on Center island need not have swam their but arrived when lake levels were lower. Furthermore neither paper addresses the many unresolved issues in hippo taxonomy and that - especially when variable of skin thickness and bone thickness are taken into account - there may have been a spectrum of densities and therefore differing buoyancy in fossil hippos. Some of the Malagasy hippos might be closer to pygmy hippos. Who knows about the Mediterranean hippos and what they evolved from and how the geological history of that area affected their biogeography. Basically it is not so simple to look at what modern H. amphibius does or does not do and infer that fossil hippos had similar capabilities or limitations. Especially so in light of the real possibility that pygmy hippos might have a different buoyancy than H. amphibius.

Hippos Best Equipped Large Bodies Mammals For Rafting

All things being equal - and even if in especially high salinities or invoking putatively  >less dense< ancestral hippos that could float or dog paddle - I still prefer rafting to colonize far flung islands as opposed to deliberate swimming and/or floating to them. Rafting solves the buoyancy issue which let's remind ourselves that no hippo of either species adult or immature has ever been observed to float or swim in fresh or saltwater for any length of time - that fact can't be ignored especially for a species so common in captivity and well observed as H. amphibius. Hippos are known for a relatively slow metabolism - especially for a mammal - and this preadapts them for oceanic voyages floating on rafts. Because hippos are known to live in estuaries and saltwater beaches they are in direct line of fire for the occasional, but inevitable, mega tsunami. mega-flood or mega-typhoon. The study of these events and how they reshuffle the deck ecologically is in its infancy. The historical and scientific record is not deep enough to document many of these events. But the geological record is. And over the course of long enough periods of time such events become not happenstance but statistical eventualities. Hippos, as long as they can get secured on a floating pile of debris or large tree, are well equipped - perhaps the best equipped out of all large mammals - to survive and take advantage of such events sporadic as they are.

The Spinosaurus Biogeography Question

Early Cretaceous. Albian

Now I finally want to tie in the two seemingly disparate narratives of this post - a potentially diverse fauna of spinosaurids in N. Africa and the likely rafting capabilities of hippos. As I mentioned in my last post I find it likely that Spinosaurus probably plots pretty close to hippos in terms of buoyancy i.e. spino is likely a sinker and not a floater. My reasoning is that underwater running/walking is most efficient with a heavy/dense body. It is quite possible that Spinosaurus did not only swim poorly - it did not even swim at all. This creates a bit of biogeographical issue as well because it could not likely disperse over land that well either. At least in the adult morph bipedalism can't currently be retrieved and it most likely moved in awkward belly sliding shuffle. Therefore Spinosaurus was limited in dispersing itself actively over deep channels of water and over long patches of dry ground.

However just because Spinosaurus could not move itself over deep channels of water or across long patches of terra firma does not mean that other geologic agents could not do the moving for it... Keep in mind that the Cenomanian was a hothouse world and the mega-typhoons/mega-floods/mega-tsunamis and just general slosh between the land/intertidal/ocean realms must have been unprecedented. All Spino had to do was hold onto that floating clump of debris/tree and sail away perhaps even to South America (hello Oxalia).

What I predict was going on is that each major river system and adjacent estuaries/mangroves would start to evolve its own unique "flavor" of spinosaur. Whether or not you would call these different species or subspecies... its a bit subjective. Once in a while environmental perturbations would shuffle up the groups so that new colonists would be spit out and formerly isolated populations would reengage. This might be what we are seeing in the differences between Stromer's spino & Spino B and FSAK-11888 that Evers et al. note -  different members of a "species complex".  Sigilmassasaurus might be its own "species complex" and it is interesting that Evers et al.'s work shows it close to several baronychines . So North Africa might just have its own giant, bipedal spinosaur that is not Spinosaurus proper!! It might also eventually prove useful to designate FSAK-11888 as a separate species from Stromer's S. aegyptiacus but still cogeneric.

However, especially in light of the taxonomic mess that is hippo taxonomy, I wouldn't hold my breath expecting Spinosaurus or N. African spinosaurid taxonomy to be sorted out neatly any time in the near future or even in your life time.



References

Evers SW, Rauhut OWM, Milner AC, McFeeters B, Allain R. (2015) A reappraisal of the morphology and systematic position of the theropod dinosaur Sigilmassasaurus from the “middle” Cretaceous of Morocco. PeerJ 3:e1323 https://dx.doi.org/10.7717/peerj.1323

Mazza, PD (2015) To swim or not to swim, that is the question: a reply to Van Der Geer et al. Lethaia Focus V-48 pp 288-290

N. Ibrahim, P. Sereno, C. Dal Sasso, S. Maganuco, M. Fabbri, D.M. Martill, S. Zouhri, N. Myhrvold, D.A. Iurino (2014). Semiaquatic adaptations in a giant predatory dinosaur. Science 26 September 11, 2014

Van Der Geer AAE, Anastasakis G, Lyras GA (2015) If hippopotamuses cannot swim how did they colonize islands: a reply to Mazza. Lethaia Focus V-48 pp 147-150

Hippopotamus, H. amphibius & Pygmy Hippopotamus, Choreopsis liberiensis 2001. revised 2011. San Diego Zoo Hippopotamus Fact Sheet


Cheers!!




http://phenomena.nationalgeographic.com/2014/09/11/the-new-spinosaurus/

credit (c) Brian Engh, used w/permision prints here

If you don't know already #Brontosmash is now a thing. Get yourself caught up to speed here, here and here. Essentially #Brontosmash (as dubbed by Mark Witton) is the bastard offspring of the SV-POW! brain trust and does a pretty dastardly job of explaining those incredible apatosaurine cervicals. Although the official paper is not out yet the picture above by Brian Engh of dontmesswithdinosaurs.com (prints here) and several others pictures/posts at SV-POW! convey an aggressively battle ready brontosaurian neck clobbering mobile armament.

Apatosaurus ajax cervical (Lview & anterior) credit Mike Taylor CC3.0

Those big, knobbly ventral bosses on the cervical may have even supported a larger growth extending out of the skin and becoming visible on the ventral surface of the neck... weird. The whole neck was strengthened and designed for powerful ventral excursions - like a giant fleshy hammer.

It seems like a pretty devastating weapon and very suggestive of some type of weaponized, ritualized combat of the sexo-social nature in these sauropods. And the very exciting and evocative artwork by Brian Engh and Mark Witton definitely capture this vibe. Pic below is available as print here.

credit Mark Witton used w/permission

However in this post I want to ratchet up the possibility for an insidiously weaponized apotosaurine war doctrine by not only invoking the neck anatomy - but also several other aspects of these animals' anatomy in a more holistic sense. What I will suggest will be startlingly brutal but also within the realm of possibility and not without comparison to several modern animal's combat technique.

As I mentioned earlier several of the depictions of #brontosmash have come to light and I like them all. What I think should be pointed out is that most of these depictions you see the sauropods coming at eachother head on or neck to neck. But others show the combat occurring with the animals more astride each other such as the one below by Brian Engh (print here).

credit Brian Engh

I want to go a little further and suggest that as the battle progressed apatosaurine combat changed realms from frontal pushing and shoving & neck strikes  - to side to side combat - and to finally the ultimate goal: pin your competitor by mounting them from above. This final act of debasement - the mount - is not without precedent in numerous animal species. Heck, anyone with even the most limited experience with dogs should be very familiar with it.

Cape Buffalo males mounting credit Jochen Van De Peer

It also should not go unnoticed that the robust foot claws of apatosaurine sauropods now come into play. The large foot claw of the front foot - a single large claw - that points medially is now firmly ensconced in the hide of the poor sauropod it is mounting. Even more devilishly brutal are the claws on the hind-feet. They have at least three good sized claws and the largest occur - what do you know - medially (or towards the midline of the body) right in the line of fire for a poor cohort getting mounted. And with all the weight involved when these claws got purchase the result could have been rib shattering and deep hide gouges.

credit Razzberyy2

Now apart from the many examples of dominance mounting in mammals there is also a group of lizards that practice mounting and grappling combat to a high level: monitor lizards.


What I really want to draw your attention to in the gif above (full video here) is how much the tail plays  a crucial role in the fight. Each lizard is constantly trying to gain leverage and tip the balance of power in its favor by using its tail as sort of a 5th limb.

Komodo dragon male dominance mounting credit NatGeo

Let's not forget that in addition to a big robust neck apatosaurines also had a big arse.... and that tail was possibly thicker around the base than the hips combined. Below is a pic of the famous ass only apatosaur mount from the Chicago Field Museum.

dat azz. Elmer Riggs' unfinished Apatosaur 1908-1958. Chicago Field Museum. stolen from this blog

credit Duane Nash

This post will serve as a bit of a primer for a series of upcoming posts on theropod behavior and anatomy in which I introduce some new arguments and argue against some prevailing memes concerning their life appearance. I thought I could put it all in one post but I didn't make it to fedex kinkos before the holiday in time to scan my artwork so you know how that goes.

I wanted to make a Thanksgiving themed post today but I wanted to make it a little different. Instead of the usual "don't forget turkeys have some bad ass relatives" digression I wanted to make the argument that turkeys themselves are bad ass and they might teach us directly about some aspects of Mesozoic theropod behavior and appearance. Namely that male turkeys - in addition to their elaborate plumage & courtship displays - also regularly engage in combative behavior, including face biting behavior (insert discussion on abundant evidence for face-biting in Mesozoic theropods).



Pretty astounding behavior check out the full video here. Such behavior is not limited to wild turkeys as domesticated male turkeys will take on all kinds of foes including roosters as shown in this youtube video below. Now right here one can insert a whole discussion on cock fights, the long history of breeding fighter birds by humans, and the ethical issues raised. But for our purposes it should be noted that such behaviors are not without parallel in the wild fore bearers of these birds.


Or this particularly violent and prolonged battle between a Muscovy duck and some variety of fighting rooster (Asil?). As you can see in the comments someone mentions that this is how dinosaurs fought and I would have to concur.





Now I want to hit you with what this post is really all about. I will do this by pointing out - what is essentially staring at you literally right in the face - is that whether or not we are talking about tom turkeys, fighting cocks, or combative Muscovy ducks is that they all share one feature in common: abundant and garrulous, usually red, facial caruncles and a mainly naked head & neck.

credit The Photographer. Cairina moschata momelanotus. Margarita Island, Venezuela CC

credit Charles Toth youtube clip

What I am saying is that the convergence of a heavily adorned, wattled, dewlapped, caruncled, and combed cervical adornment in these three highly combative modern aves should not be glossed over. Usually interpreted as sexo-social signaling devices - and I am not disputing this adaptation - I think that they offer another, more functional usage. That is that in combat they offer up a convenient - and brightly colored - choice target to get bit upon. Why would a combative animal have such evolutionary pressure to offer up a choice morsel to get bit upon? Because losing a chunk of skin is preferable to losing an eyeball!! Feathers would be less than ideal because once plucked out little defense is left.

To embellish my point let's not forget to mention both old & new world vultures which are often bald headed and heavily caruncled. Except for these birds such features may offer more utility in fights over territory and food as opposed to sexo-social battles as in the other birds mentioned.

Red-headed vulture. credit Shepherd, Dayton OH CC

Andean Condor. credit Flickr Art G. CC

lappet-faced vulture. wiki-commons

Long time readers of this blog should not be surprised that I have been heralding both new and old world vultures as the best modern analogue to generalized, serrated toothed Mesozoic carnivorous theropods for quite some time now. People just need to get over the "scavenging" stigma for these animals - they offer more utility than sharks or monitor lizards in terms of how Mesozoic theropods behaved, moved across, and partitioned the landscape. Not only do sharks and monitor lizards fall down compared to theropods in terms of just about every meaningful gross anatomical/metabolic characteristic but the trait that is usually put forth as the unifying character linking these groups - serrated teeth - as I argued here both old & new world vultures (and giant petrels) have likely evolved an equivalent method of cutting and shredding carcasses: choanal grinding. Furthermore giant petrels, and both new & old world vultures are, you know, actually living derived theropods so there's that but it always seems to be that parsimony goes out the window with these things because TEETH. Get over teeth - modern day derived, soaring theropods are consuming more flesh on the African plains than all those "toothed" mammalian carnivores combined.

So when I stumble upon a youtube video (full video) showing essentially gang-turf warfare between two familial groups of black vultures (Coragyps atratus) and it has got "only" 711 views I got to raise a little ruckus. Not only are black vultures highly opportunistic and bold in their foraging - taking everything from turtle eggs to newborn calves - they also have evolved a kin-based group foraging method, are fairly terrestrial, and - as suggested by the author of this video - engage in territorial combat. Long story short this is the closest we are going to get to watching Mesozoic theropods engaged in combative face biting behavior. So I find it a little ironic that this window into the past is blatantly overlooked by a society supposedly obsessed with dinosaurs, especially face biting tyrannosaurids. Check out towards the end (about 20 second mark) where a chuck of one of the vulture's face gets ripped off and another vulture quickly gobbles it up.



"Now wait a secondI thought group foraging was fairly rare in predatory birds and only Harris's Hawk regularly hunted in any sort of group hunting method?" 

Black Vulture wiki commons

Which brings me to my next point. Theropod interpretations both behavioral and appearance wise- especially dromaeosaurid - have been hoodwinked by the "hawk" analogy to a large degree. I presume this is because of the "predatory" nature of classic "raptorial clawed" accipitriformes. What is not in dispute is that hawks, eagles, owls, they do engage in some pretty startling and daring predatory ventures which I think capture the imagination and get us thinking about Mesozoic theropods. However  what should not go unstated is that "raptorial clawed" raptors of all ilks are dominated by a feet first method of predation. The head is almost never involved in the actual killing or subduing of prey except after the claws have sufficiently weakened the prey. This trend is immediately apparent in the startling video here of an eagle going after a very large ruminant and the prolonged battle. Never once does the eagle interface its head with the prey despite the rough and tumble engagement.



This trend of foot first predation with the head essentially not interacting with the prey until after it is killed or incapacitated is in stark contrast to generalized predatory theropods which all - even dromaeosaurids - maintained good sized jaws and serrated teeth. Dromaeosaurids never became >as specialized< in foot dominated predation as eagles, hawks and other raptorial birds of prey. The head remained a useful and probably necessary tool in prey acquisition and dismemberment, not to mention combat both intra & extraspecific.

credit Luis Rey. Maybe he was right all along? Link Deinonychus saga

Therefore, I argue, when restoring theropod heads - especially feathered - look more towards old & new world vultures, turkeys, chickens, muscovy ducks and other face biting highly combative birds than "classic" raptorial birds of prey. Give 'em mainly naked heads and necks, gnarly protuberances, grizzled bumpy ridges, combs, wattles, quills and frills. An apparent nape of thick feathers - like in many vultures and analogous to a lion's mane is quite defensible. In essence, make them less pretty. But please don't make 'em look like ground hawks because such birds don't kill or even really fight with their heads. Exception being theropods that lived in especially cool climates they likely had feathers all over just as cool adapted Lammergeiers have fully feathered heads. If you go look at all the artwork that came out surrounding the new Dakotaraptor it will very quickly become apparent that they are all just variations on the same "ground hawk" riff meme. The head is restored usually after a red-tailed hawk or peregine falcon.

Dakotaraptor Emly Willougby CC4.0

Ask yourself, what do we really have in terms of full body feather preservation for medium-largish generalized dromaeosaurids? Not much really. Microraptor hardly counts as it is small, fairly specialized, and lives in a cool environment anyways. So I say better to look towards the birds that actually do combative stuff with their heads as opposed to hawks and eagles which don't really engage their head in battle much at all...



Gobble, Gobble.

One theme that I keep addressing in this ongoing theropod series is that theropod table manners at large carcasses (i.e. who gets to eat what and when they get to eat it) is a subject of much natural interest but has received relatively little rigorous scientific attention. Instead much research focuses on how prey or landscape is partitioned but what about how large carcasses were partitioned? What I mean by this is that when we look at large carcasses - especially giant sauropods or even some of the bigger saurolophine hadrosaurs - this is a bonanza of resources that just begs to be exploited by the local theropod population. And I mean, the whole local theropod population...

There is a recurring sentiment that I keep coming across in theropod research - that overemphasizes niche partitioning to an extreme. "The young of such and such tyrannosaur species had different jaw mechanics and therefore ate different prey than the adults." Or the other corollary that "multiple coexisting large theropods had some almost benevolent driving force admonishing them to concentrate on different food stuffs to avoid too much competition etc. etc." And this is probably true to a certain extent I have to concede. However too often we assume that extreme partitioning has to occur. Modern examples beg to differ. For example lions and spotted hyenas are both social, live in the exact same habitats, and have significant dietary overlap.

When the shit hits the fan environmentally - when all the small prey has went into torpor, when all the fish have retreated with receding water or aestivated in the mud, when all the young dinos have migrated out of the neighborhood - that is when the true crucible of theropod competitive fires is stoked.  That cauldron I speak of is who gets to eat what, how much, and when at carcass gatherings. This really should come at no surprise when we look at how modern theropods i.e. birds partition carcasses especially in times of environmental stress. Let's forgo the vulture example because it is too obvious and instead pay some credence to the importance of large carcasses to many passerines, corvids, and raptors in areas of extreme winters.


What I want to attract your attention to is a sentence towards the end: "As snow depth increased, jays and great tits increased scavenging. We suggest that carrion use by scavengers is not random, but a complex process mediated by extrinsic factors and by behavioural adaptations of scavengers."

Most readers of this blog are in know well enough to be aware of carcass utilization by such birds but I think it bears a little reinforcement that such usage is often linked to environmental stress - in this case heavy snow. In the Mesozoic it could as well have been a devastating drought. In such circumstances partitioning for theropod dinosaurs as it is often invoked goes out the window and truly weird menageries of scavenging theropod guilds potentially gathered at carcasses. Yes I am even looking at theropods traditionally interpreted as herbivorous, insectivorous, and omnivorous such as ornithomimids, oviraptorids, alvarezaurids and therizinosaurids potentially joining the cue to exploit carcasses in such circumstances.

Chickadee scavenging elk carcass credit Jacob W. Frank

As interesting an aside as the thought of therizinosaurids moving in to scavenge among more traditional predatory theropods is, the take home message I am trying to convey is that such feeding bouts at  carcasses likely shaped theropod social and behavioral ecology. Furthermore it is also entirely possible that some theropods developed intimidation and defense mechanisms to gain leverage at such dinner parties.

Among mammalian carnivores we don't often think of them having defensive mechanisms at hand or combative/intimidation arsenals to dominate carcasses - aside from their teeth and claws - and growling/hissing. Social carnivores can dominate carcasses in relatively cohesive groups but, especially among solitary felids, retreat is the usual option - even when faced with throngs of scavenging birds. Several bears - armed with bulk, a thick skin, and a fat layer - are well provisioned for carcass monopolization and spotted hyenas with size, thick skin, muscular forequarters, strength, and group tactics also come to mind.

However among several extant diapsids better analogies exist that offer lessons in Mesozoic theropod table manners. Crocodiles and komodo dragons have dermal ossifications embedded in their skin which offer utility in rugged feeding encounters. It is also little appreciated that nile crocodiles will swarm en masse to drive off land based predators from carcasses. Which suggests some semblance of, dare we say it, "group social tactics"



Despite the attractiveness of looking towards big toothy lizards and crocs when it comes to how Mesozoic theropods monopolized carcasses we are literally spoiled with analogies among modern theropods that regularly feed on such foodstuffs: giant petrels and vultures. No need to look so far away phylogenetically when we have, you know, actual dinosaurs that do this stuff today. Furthermore not only are carcass feeding vultures and giant petrels better analogies phylogenetically, they are, let's be honest here,  a lot cooler to watch around carcasses than big crocs, monitor lizards, or mammalian mega-predators anyways!!




If there is one word I can use to describe these birds around carcasses it is theatrical. I really love this video of giant petrels gesticulating around a pinniped carcass. Not only does the video have a nice, grainy 1980's VHS gore movie quality to it the birds put on quite a dramatic show. The racket raises some questions - at least for me - about what these skirmishes really mean. There appears to be enough food there for all the birds yet the battles, both mock and actual, never let up. Are these confrontations really about setting up a pecking order when food is actually not so easy to come by? Another observation I want to draw attention to which I will return to later is the use of outstretched wings to maintain a "zone of influence" on the carcass that keeps other birds at bay.


Of course I would be remiss to not pay heed to one of the great Grande Guignol Theropoda performers of all time - the always on point lappet-faced vulture. Such presence. Such gravitas.





Note also in this portrait I am painting of intensely theatrical, gesticulating, and combative carcass skirmishing theropods, the last post I made on face biting theropods plays directly into this one. Grotesquely adorned, carnuncled, and gnarly faced/necked/forequarters would have all come into beautiful display and usage in such barbaric feeding bouts.

With these disturbing thoughts and images swimming inside your head let us revisit the paradoxical situation of the ulnar quill knobs in Convavenator. I refer to the situation as paradoxical because - although the trend of increasing "birdiness" in theropods is certainly a thing (or is it that increasing theropodness in birds is a better way to put it?) Concavenator was truly and squarely a carcharodontosaurid. These "land shark" megapredatorial theropods were not becoming birds nor were there antecedents on the way to or from flightedness. If anything they seem to be going in the opposite direction with smaller and smaller forelimbs and pretty much dedicated to hyper-carnivorous ways with out even the slightest hints of even an omnivore among the ranks. It is weird that quill knobs implying some sort of feather quill in these theropods appears, almost like evolution by proximity?

from Ortega 2010

There has been some skepticism which, as far as I know has been some critiques voiced online by Darren Naish and others (at least according to Wiki) that the irregular placement of these features argues against quill knobs and that they can be ulnar muscle scars. Addressing these contentions is an abstract presented at SVP2015 by Cuesta, Ortega, & Sanz that, well let me just cut and paste the abstract in their own words.

So their work seems to indicate that muscle scars don't best explain the features and that there is more diversity in these features placement in modern birds than generally assumed. Let us for arguments sake assume that their findings are valid and robust that as they put it "indicates the presence of skin appendages in Convavenator, preceding the wing feathers present in Maniraptora".

Note the careful language that they use calling them"skin appendages" instead of feathers and "preceding the wing feathers in Maniraptora".  I think that Cuesta et al. were very intelligent in making these semantic distinctions. What was most likely there - and what is most likely the most basal integument in dinosaurs - is literally a simple, shaft "quill" type feature.

The important word to keep in mind here is "quill" and here I want to revisit the observation I drew your attention to earlier of giant petrels establishing a "zone of influence" with outstretched wings at carcasses. If we imagine sharp and robust "quill" type appendages attached to these notably unusually placed "ulnar knobs" then it is not too hard to imagine their obvious utility at feeding bouts. Like the giant petrels earlier with wings outstretched these posteriolaterally projecting quills would help Concavenator"elbow in at the dinner table" among other theropods.

Concavenator"Mouth For War... Last Fix2" by Duane Nash

Of course such a general theropod gestalt has been portrayed before. Brett Booth has been drawing spiky projections coming off the arms of theropods for some time now. BTW what happened to that artist?



Such devices remind me of the ludicrous spiked arm gauntlets worn by some black metal artists. I do recall going to several punk/metal shows and how studded shoulder spikes and wrist spikes were a definite and dubious threat in the mosh pit and became banned at many venues for their danger!!




Here I wanted to depict three very different predatory theropods Concavenator and a mega-dromaesaurid and baronychine converging on a Pelecanimimus carcass. Normally there is some dietary partitioning between these predators but a drought has forced them into proximity and competition over carcasses. With it's spiked and uncouth countenance the Concavenator is able to monopolize the carcass.

Theropod Table Manners Gone Bad by Duane Nash

It's also worth noting that the outstretched wings of maniraptorine theropods could serve a similar function at carcass disputes - serving to both intimidate and establish a zone of influence at carcasses.



Cheers!!

References

Referencia: Cuesta, E., Ortega, F., Sanz, J. Ulnar bumps of Concavenator: Quill Knobs or Muscular scar? Myological Reconstruction of the forelimb of Concavenator corcovatus (Lower Cretaceous, Las Hoyas, Spain). Abstracts of papers of the 75th Anuual Meeting of the Society of Vertebrate Paleontology: 111-112.

Naish, D. (2010). Concavenator: an incredible allosauroid with a weird sail (or hump)... and proto-feathers?. Tetrapod Zoology, September 9, 2010.

Ortega, F.; Escaso, F.; Sanz, J.L. (2010). "A bizarre, humped Carcharodontosauria (Theropoda) from the Lower Cretaceous of Spain" (PDF). Nature 467 (7312): 203–206. doi:10.1038/nature09181.PMID 20829793.

Selva, N.; Jedrzejewska, B.; Jedrzejewska W.;  Wajrak, A. Factors affecting carcass use by a guild of scavengers in European temperate woodland. Canadian Journal of Zoology December 2005 83(12): 1590-1601 pdf

This post, necessarily in my opinion, addresses both a social and scientific melange surrounding that guy and his cohorts - the tyrant lizards. I have been putting off talking about Tyrannosaurus rex and the tyrant lizards in this theropod themed kick I have been on lately because what really is new to say about them? I mean they are probably the most studied group of dinosaurs nay prehistoric critters of any type and we probably know more about not just the anatomy but foraging/biting behavior of these animals than many extant predators such as sperm whales or several giant deep sea teuthids.

To give a bit of a qualifier here I really do love and adore the tyrant lizards. I and probably several of you reading this post would likely not be here if it wasn't for them. I mean that head, the bite force, the whole package is just iconic. However I do think it necessary to take down these animals a peg or two relative to other theropods. Ok, ok maybe not take tyrannosaurids down a peg so much as elevate other theropods. I think that - both culturally and scientifically - tyrant lizards have become too much the yardstick for what it means to be a hyper-carnivorous theropod. It should always bear repeating: these animals are overgrown coelurosaurs largely independent in descent from the other large carnivorous theropods.

People love stories, are drawn to them, and understand the world through stories. When we look at the story of theropod evolution it should not go unnoticed that tyrannosaurids, and most pertinently Tyrannosaurus rex, appear at the end and culmination of the dinosaur saga respectively. I know that will be common knowledge to my readers but just breath that thought in for a second: Tyrannosaurus rex not only was for many years the largest recognized theropod but it was one of the last. The fact that it occurred in the American west only adds to the lore, mystique, and seemingly manifest destiny of this penultimate theropod to lord over all other theropods.


It is, when you really stop and think about it, quite amazing the coincidence of the largest, biggest, baddest, and last hyper-carnivorous theropod occurring at the death knell of the Cretaceous in the eternal frontier of the American west... quite a good story if you unpack it a bit. With these thoughts swimming around in your head it should come as no great stretch to imagine a popular narrative unfolding: Tyrannosaurids and Tyrannosaurus rex represent the apex, the gold standard of theropod evolution, all other theropods were lesser versions of this last and final model.

The take home message being that yeah Allosaurus was all right but it was merely a lesser, imperfect version of Tyrannosaurus rex. Mapusasaurus was cool, but still not a tyrannosaurid. Crylophosaurus, pretty neat but no T. rex. What this is all smacks of is some real neo-Lamarckian thinking. As if, for 140 million years give or take of theropod evolution, theropods finally get it right with the tyrannosaurid model after many botched, failed attempts.



Of course this way of thinking about evolution is inherently wrong. Organisms are not striving to become some ultimate model or have some type of end game in sight. Evolution is blind and groping and just hobbling together with the best fit jerry-rigged from existing parts at the time. Unfortunately I think we - including some paleontologists - lose sight of this picture and play a little bit of Monday morning quarterback with interpretations of past organisms. If failed, botched attempts are such a hallmark of the fossil record then where are they now in our present biota? What animals represent such evolutionary hiccups?

This is of course a cultural unpacking - that is not too great a controversy I am sure we can all find some truth in. But what I believe is that this narrative has spilled over into the scientific realm. What I speak of - the controversial bit I can not dispense with - is the notion that tyrannosaurids in general and Tyrannosaurus rex in particular were far and away more devestating, powerful, and all consuming than other hyper-carnivorous theropods.

Where I think this line of thinking gets the greatest cashet is the notion of bone consumption and dismemberment among tyrannosaurids - a topic of much interest for me. The general gist of tyrannosaurs being elevated over other theropods, by both lay and professionals, is most succinctly summarized as such: "only the great tyrant lizards - especially Tyrannosaurus rex - had jaws robust enough and teeth strong and stout enough to pulverize and consume bone". And the corollary: "Blade toothed theropods (i.e. everybody else besides tyrannosaurids) avoided bone assiduously and were especially careful eaters".

These statements have become a bit of a mantra among both fans of dinosaurs and most professionals. They all tow the party line - tyrannosaurids ate bone but other theropods did not. But the way I read it is different. For some reason theropods waited more than 140 million years to eat bone? Furthermore blade toothed theropods not only had to have been especially careful and dainty eaters to avoid chipping a tooth while biting into the internal bone of dinosaur prey, but had to be careful in biting into the skin of a wide variety of dinosaurs? The reason is that osteoderms - bone growing in and essentially embedded within the skin - is especially widespread among dinosaurs!! Nodosaurs, stegosaurs, ankylosaurs - essentially all thyreophora - had osteoderms. Among sauropods titanosaurids seem to have been especially bony skinned. And osteoderms were especially abundant among the various archosauromorphs that evolved with the first theropods. Blade toothed theropods lived with and evolved with osteoderm bearing animals for pretty much the duration of the Mesozoic. To take this notion seriously - that blade toothed theropods were so careful and selective in biting into their fellow prey species - is patently ludicrous in my opinion and just flies in the face of what it takes to have been at least a somewhat competent predator,  much less the most successful and persistent radiation of terrestrial vertebrae predators ever.

And besides these two arguments is the evidence of deliberate, unequivocal and sometimes alarming bone cutting, chewing, and consumption that can only be attributable to blade toothed theropods.

Tyrannosaurus rex gets all the headlines in terms of bone consumption but if you really investigate all the lines of evidence it falls short compared to blade toothed theropods in two pretty notable categories.

1) The largest and most bone riddled theropod coprolite does not - as often claimed - belong to the tyrant king but actually is the work of a particularly bone hungry Allosaurus way back in the late Jurassic. I talked about this little known tid-bit on my post on Allosaurus feeding mechanics here but it is worth a reprint:





A turd 1.52 meters long!! And 50% of it is of bone fragments - not whole bones but minced shards of bone. Exactly what would be expected to occur in the "bonesaw shimmy" method I postulated. It is worth reiterating that bone passes largely undigested through theropod guts and there is no evidence of gastroliths in Allosaurus. This bone chipping was being done in the mouth, not the work of a bone cruncher but a bone mincer.

T. rex (L) and Allosaurus (R) Two solutions to the same problem, A bone cruncher and a bone saw

So T. rex can not lay claim to the biggest and most bone riddled turd we know of.

2) The "tyrant lizard king" can not even lay claim to the biggest and deepest score marks on bone. The largest and deepest score marks on bone comes from an unknown early Cretaceous theropod that left traces on some giant sauropod caudal vertebrae in Korea:


These deep scores are not the work of T. rex nor are they likely the work of any classic late Cretaceous style "bone crunching" tyrannosaurid. Although a tyrannosauroid can not be ruled out here it is worth noting that early Cretaceous tyrannosauroids had a lot more in common with other blade toothed theropods than the latter bananna toothed killers.  I consider earlier tyrannosauroids as likely candidates for the "bonesaw shimmy". I also am starting to seriously consider that the young of giant tyrannosaurids as well as alioramids as likely candidates for neck driven vibrational feeding.

Alioramis. All the hallmarks of a true chainsaw mouth. credit SteveoC CC3.0

I think the question that we should be asking is not why did blade toothed theropods fail where tyrannosaurids succeeded in bone consumption because a thorough review of multiple lines of evidence suggests that blade toothed theropods evolved a parallel method of bone processing (i.e. chainsaw mouthed, neck driven "bonesaw shimmy" in my opinion) but what made tyrannosaurids so different from the vast majority of carnivorous theropods? That is the question in my mind although I don't really have a precise answer. Some have suggested ornithischian dominated habits stimulated a crushing/pulverizing bite. I am not certain as there were nodosaur and iguanodont dominated formations in the early-middle Cretaceous. Gregory S. Paul often spoke of an arms race between tyrannosaurids and their prey - perhaps part of this arms race involved the increasing dermal thickness of prey species? Additionally the pulverizing bite of tyrannosaurids may have allowed for more quicker and efficient killing than blade toothed theropods and therefore more time to consume prey before competitors and especially conspecifics showed up to challenge for a bite. Likely a combination of these and multiple factors...

Why have tyrannosaurids, and especially T. rex, received all the attention for bone consumption?

Well, in addition to the narrative I have played up so far, I think that there are several not entirely mutually independent reasons.

1) The pull of the recent. Tyrannosaurid bearing formations are younger, well sampled, well studied, and generally get a lot of attention. Western North America in particular. For many of the formations such as Dinosaur Provincial Park or Hell Creek there are so many good remains that meaningful statistical analyses can occur. I don't think you can do the same for let's say middle Jurassic Chinese stegosaurids or early Cretaceous Australian titanosaurids. We just have better representation of tyrannosaurid dominated formations and therefore "see" more evidence of bone utilization.

However, even from my armchair analysis of what I find peppered on the web I keep coming across published and more anecdotal references of bone chips in theropod coprolites or - especially in the Morrison formation - quite dramatic unpublished and published tooth marks on bones. I mean, check out this carvery done on a Camarasaurus ilium. Can you really chalk that up to "incidental contact"? From SV-POW credit Matt Weddel used w/permission.

theropod damage on a Camarasaurus ilium. credit Matt Weddel SV-POW

2) The hyena mindset. Bone crunching not bone slicing or mincing is how we are "prepared" to think about bone utilization since that is what the most famous bone consumers hyenas do. Since we have this mindset in place already we "expect" stout bananna toothed tyrannosaurids to access bone but blade toothed theropods not so much. But when direct and unequivocal evidence of bone utilization in non-tyranosaurid bearing formations is found it seems to be discounted, ignored, explained away, or even sometimes attributed to some unknown crocodile or as yet undiscovered lineage of tyrannosaurid in the late Jurassic or early Cretaceous. Not to, you know, the blade toothed theropods that actually lived there.

What is interesting when we think about the hyena analogy is that hyenas - which we can all agree are bone consumers - do not indiscriminately eat every scrap of bone available to them. In fact this study  on the extinct giant hyena Pachycrocuta makes the point explicit. Marrow rich long bones were highly sought after but other bones left relatively unscathed. Tyrannosaurids likewise did not eat every scrap of bone available to them - in fact there is much evidence of nipped and delicately stripped bones by tyrannosaurids despite their awesome jaws and bone crunching dentition. So just because you can eat bone doesn't mean you eat it all the time, eat other parts preferentially, or just ignore the bone. Some bones in dinosaur carcasses - especially highly pneumatic ones - were likely left alone. The more marrow rich bones in dinosaur carcasses - which no one really knows which ones they are although I suspect the ilium, caudal vertebrae, and some ends of long bones - may have been more heavily exploited.

Let us escape from the paradigm of bone crunching and think about sharks and shark attacks for a bit. Reading about shark attack accounts is both horrifying and terrific. What is amazing about them is that they are rife with accounts of sharks cutting through and sawing through human bone, literally dismembering humans while still alive. Happens all the time. These are sawing animals, not hyena like crunchers. We know from the work of Brinke et al (2015) that theropod teeth were mechanically stronger than other ziphodont predators and likely better rooted and reinforced than shark teeth. In my estimation there's nothing a shark could do that a similar sized blade toothed theropod couldn't do. Sharks shake their body left and right to allow their serrations to work their way through hard objects. Theropods shook their neck and/or body fore and aft to allow their serrations on the front and back end of their teeth (labial & lingual) to work their way through tough objects.



However, for whatever reasons these nuanced conditions that determine when to eat or not eat bone go out the window when we talk about blade toothed theropods. Despite the fact that for many dinosaurs - and especially sauropods - we have a sample size of n=1 so, unlike the abundant hadrosaurids and certatopsids in tyrannosaurid formations, it's sort of hard to make any meaningful claims on the frequency of bone exploitation in large sauropod dominated formations.  However it is also worth mentioning where are all the juvenile, teenage, and subadult sauropods in formations dominated by blade toothed theropods? Not all sauropods would have been whale sized behemoths. In any sauropod population numerically there would have been many more elk, water buffalo, rhino, and elephant sized sauropods than whale sized adults. Where are they all? These would have been sauropods too big to be swallowed whole (the baby killer specialist scenario as postulated by Dave Hone) but large enough to have easily been preserved in the fossil record. So where are they all? If blade toothed theropods were assiduously avoiding bones we should have them or at least their bones... Could it be that blade toothed theropods were in fact "disappearing" entire carcasses Joe Pesci style? ( a future post hint, hint) Let me flip the script here a bit and suggest that blade toothed theropods were eating more bones than tyrannosaurids - in fact they were eliminating entire size classes of sauropods from entering the fossil record. After all it is blade toothed theropods that hold the record for largest bone riddled poop and deepest bone score mark on bone - not the tyrant lizards.

heavily worn Carcharodontosaurus tooth. paleodirect

ditto. note wearing down of tip

The startling and unprecedented cavalcade of evidence of definite non-scaly integumentary structures on dinosaurs stands as one of the most exciting developments in dinosaur research over the last several decades. Whether in the form quills, feathers, pynofibers or any of the variously described features put under the banner of "dino-fuzz" these features continue to bedazzle us, further blur the line between dinosaur and bird, and offer up important new vistas and possibilities as to what and how dinosaurs looked and behaved. A speculative movement towards "enfluffening" - that a more widespread and encompassing integumentary parade of dinosaurs of all sizes and stripes was likely - has come into vogue. At the acme of this development are speculative depictions of shaggy coated arctic ceratopsids, woolly sauropods, and furry ankylosaurs.

It's no secret that a life dedicated to paleontology - either professionally on some level or as an artist, writer, "paleopersonality" or whatever - is a life flirting with poverty or more often than not wed to her. To the few that can get through the prescribed pathway of multiple years of education towards a "piled higher and deeper" tagline at the end of your name and compete successfully for the  few academic positions or that can make a living off your art and writing kudos to you!! (I can't do it that is why I am a bus driver) But even among the noted luminaries of the field of dinosaur paleontology - artistic or scientific or a blending of both - I often hear of economic hardships.

I thought I could get through this post by taking the high road and not naming names but alas... I can't so let the dirt fly...

A couple of years ago there was a big brewhaha over Gregory S. Paul attempting to lay claim - in fact legal copyright ownership - over his distinctive stylized skeletal rendering method.  I don't know if it ever went fully to court but at least the threat of legal pushing seems to have discouraged artists from utilizing his "Paulian push off" stance in their skeletal mounts. I can't really say that this event resulted in more work for Paul, in fact the exact opposite seems to have occurred.

To say that Paul's work, especially during the 80's and 90's, was extremely prescient and foundational towards where we are at now in dinosaur paleontology is an understatement. After all, feathered dinosaurs are now a thing but they certainly were not in the minds of most pre-eminent dinosaur paleontologists/paleoartists in the 70's, 80's and much of the 90's.

Never the less the underpinnings of Paul's work that underscore contemporary dinosaur thought has not  made him a rich man from what I gather.

Which is why I can not completely condemn him for lending his name to the recent children's dinosaur book Ancient Earth Journal: The Early Cretaceous Notes, Drawings, and Observations From Prehistory Amazon.



At first I was quite excited for the prospects of an illustrated children's book on early Cretaceous dinosaurs by Gregory S. Paul. I love Paul's work and have not seen much new from him in a while and I was curious to see if a children's book would give him some nice freedom and liberty to illustrate some new concepts or ideas?

But nope. I was hoodwinked.

The amazon description and the cover is misleading (directly misleading perhaps?) because both Juan Carlos Alonso and Gregory S. Paul are listed as authors. When I opened the book and skimmed the artwork I was confounded, had Paul drastically changed his style? Nope, upon closer inspection on the inside sleeve I saw Paul is the writer while Alonso is the illustrator. Now Alonso is OKish I guess - some of the theropods, pterosaus, birds and sauropods are pretty good - but his ornithopods and some of the weird stances he uses just look... painful. For Paul to have a dino book without a single one of his illustrations in it? Why?

But maybe the text Paul put in would save this book... nope again. The writing is boring and dry. No exciting vignettes or exploration of ideas, concepts. Same critique I leveled at Switek's & Csotonyi's book. Nothing new to see here folks. Keep in mind that Paul is an excellent writer who wrote this in PDOTW:

"The T. rex is a monster of ten tonnes, her frightful face adorned with hornlets and scales and a red stripe before the eyes. Mottled green and brown camouflage makes her look like a NATO tank lurking in the brush."

Now that paints a picture, even to a six year old. All I can do is conclude that as one reviewer on Amazon put it "Paul was there to take a check". To make the worm turn further for pterosaur lovers there is also skim feeding pterosaurs in the book. Skim feeding.

Which is the same conclusion I drew after reading Switek & Csotonyi's book. Or Jack Horner acting as consultant to Jurassic World. Cash grabs.

Some or even most might take exception to my tone, "money talks bullshit walks" after all and these people have done a lot and continue to do a lot for paleontology so why not skim a bit off the top? Even if it is the kids taking it on the chin with imo lazy, hackneyed, "place holder" type books. Please keep in mind that both Prehistoric Predators and The Early Cretaceous books are actually among the better paleo books for kids out there. They are like the floating turds in a sea of crap...

Certainly I can be charged with speaking from a high horse. It is easy not to sell out when no one is attempting to buy you off. So in addition to calling out these obvious cash grabs let me offer a potential way of thinking about the larger problem of economics in paleo.

The problem I see it is not subpar, cash grab "name-brand recognition" type books but the financial hardship and the economic woes at all levels in paleontology (dinosaurs being loosely synonymous with paleo here). It's the economy stupid. The real point of this post is to look at the conditions that foster these types of work.

The paleoeconomy is losing market share at tremendous levels. And we are losing this market share at exactly the wrong time demographically - when people actually have disposable income to spend on things like dinosaur prints. Or fund massive dig sites. And we have no one to blame but ourselves for not recognizing the problem and putting a plug in the leak.

People are losing their dinosaurs all over the place and the paleo-community is doing little to stifle this leak and if anything is hurting the situation.


Think about the problem as if you are in charge of a corporation. It is patently obvious that children love dinosaurs. From a strategic, marketing standpoint this is exactly what you want. Name brand recognition and a strong - even emotional - attachment from an early age. Dinosaurs (read paleontology) do all the work for us just by simply being so large and daunting to young minds. So what we have in paleontology is a situation that should be the envy of any corporation - strong, emotional attachment by a wide swath of the youth market from the get go. Corporations spend incredible amounts of money and research trying to capture market share at a young age and paleontology has youth attachment built into it. But somehow paleontology does not retain this built in audience...

We lose most of the kids, usually around puberty in most cases I suggest, right before they are on the cusp of joining the work force and having actual disposable income to give to the paleoeconomy. This is tragic and what is doubly disheartening is that we do it to ourselves a bit. Let me elaborate.

Marginalization of the "Fan-Boy"

The long-standing dirty little secret among a great many paleontologists, researchers, enthusiasts, or just life long fans is that there is a little bit of the fan-boy (or girl) in all of us. Something resonated with us at an early age that  caused this emotional attachment to the form of a T. rex skull, or the sail on the back of dimetrodon, or the sabre tooth of a smilodon. When we are emotionally attached to something we sometimes don't think logically about it. Which means we don't think scientifically about it. And in the world of the internet where everyone has a voice and at times everyone seems to have a voice that is not very tolerant, empathetic , or nuanced for the most part the term "fan-boy" has become equivalent to what is wrong with paleo-culture.

I see it all the time in forums, discussions, comments sections - the "fan-boy" getting torn to shreds. Keep in the mind the person you are talking to - or berating - online might be all of eight years old and not too different from you when you were starting to pursue this topic with gusto. So take it easy on the fan-boy who - if he/she is not driven from the topic by online attacks - might be a professional paleontologist one day or financier of paleo.

If I can speak from my own experiences - dating myself a bit here - I reacted to shock and horror at the thought of sauropods not wallowing around in swamps because I had grown up with that image, it had emotional resonance for me (yes even during the 80's this idea sauropod in the swamps meme was prevalent). Even as a teenager I was disbelieving in the rather solid argument that fully grown T. rex could not sprint along at 45 mph.

The key is to outlive this "fan-boy" phase until more adult, reasoned, and scientifically minded thinking kicks in. For a thriving paleoeconomy we should explore and address ways to bridge this gap so we don't lose fanboys to stuff like manga or gun collecting. Because once we lose them we lose a potential adult customer that now has actual capital to buy paleo books, finance digs, or fund kickstarter or patreon campaigns.

So be tolerant of "fan-boys" encourage their interest and try and be a mentor or teacher to them. It can be hard, I know.

The Myth of Childhood as the Province of Dino-mania

Dinosaurs are just for kids right? Wrong. If anything dinosaurs have gotten a lot cooler to me as an adult. Never the less I do get a lot of glazed over expressions when I tell adults that I write about paleontology and dinosaurs on my blog. The conversation seems to end. I am not one to push dinosaurs on anybody but it always confounds me that they have no questions about dinosaurs or paleo... they lost their dinosaurs a long, long time ago - so sad.



But what about the Star Wars phenomena? There is certainly some child - like attributes to that series but here you see fully grown men in costumes, waiting over night for premiers, and just generally going ga-ga over the space drama. And they are all keeping the flame alive for a fascination that started since child hood. Dinosaurs inspire at least as much adoration in children as Star Wars but why does Star Wars keep people reaching into their pocket books well into maturity but dinosaurs not so much?

Lessons From... Punk Rock?

Readers of this blog know that I am a bit of a music buff and will try and sneak in musical references and clips of my two favorite genres of music heavy metal and punk. An interesting development has occurred in punk rock of all music in recent years. It is now old people music. Yep, punk rock is now Dad rock. Now that old people with stable incomes and disposable cash are nostalgic for the music of their youth we see punk bands capitalizing, touring, and selling merchandise at levels far above what they did in their prime, formative years when they and their fan base were broke.



Just as in the example above regarding the Star Wars franchise punk rock -  a symbol of youthful rebellion if there ever was one - is readily commodified, repackaged and sold back to fans that enjoyed it in their youth but now have the income to really support it financially.

If Star Wars and punk rock can both capitalize on and keep ensnared a once youthful but now largely adult audience why not paleontology? Why does the paleoeconomy keep losing market share precisely when the demographic is coming of age and starting to acquire capital to spend? Why are so many kids ensnared by dinosaurs but lose interest with age while in a minority the interest remains steadfast or even grows?

I don't have the answer to that last question but I do feel we need better bridge building from the youthful, emotional, "fan-boy" mentality to adult, scientifically minded and - most important - disposable income having adult paleo fans.

So in conclusion...


I would love to see a day when I don't  have to keep calling out very talented individuals that, imo, lend their names to children's books and other projects on dinosaurs to get a quick pay check. I think we underestimate the level and the interest children can be communicated to scientifically. At the same time there is a growing up phase in paleontological interest and pursuits. And the fan-boy mentality is certainly part of this process. The key is - economically - to retain the fan-boy until they graduate a more nuanced, scientifically minded way of  looking at paleo. Which I suggest will often coincide with their entrance into the work field (i.e. more disposable income than teenagers/children). Given that I argue that there is a little bit of a fan-boy in all paleo-fans and especially paleontologists we should be empathetic to this stage and we do ourselves a disservice when we berate or belittle this mentality in online forums/chats/social media etc etc. (which btw I have seen professional paleontologists do all the time) which might actually drive them away from the subject entirely. Instead when dealing with fan-boy behavior stay patient - be a teacher - don't try and embarrass or belittle them online. The fan-boy that the paleontological community retains today will grow up mentally (well maybe not all of them) eventually and, further on down the line, have the financial recompense to pay back the paleo-economy.

If paleontology - especially dinosaurian - was smarter as a business it would aim better to keep and maintain the youthful audience it has built into it from the start through audulthood. Why gifted and talented paleo artists, writers, and researchers have to petition online for cash disbursements from a vanishingly small market when other genres (Star Wars, punk rock) retain their youth market into adulthood is a major stumbling block towards creating a sustainable paleoeconomy. That many or most of the most talented practitioners in paleontology are constantly ensnared or flirting with poverty is a travesty of the highest order.

Postscript, as further evidence that the internet meta-brain is at work David Orr from Love in the Time of Chasmosaurus coincidentally put up a nice list of paleo people you can support on patreon.

Faster Spino!! Run-Run-Run!! by Duane Nash click image for larger view

I am not completely averse to Spinosaurus bounding around on two legs. You will note I did depict the spinosaurs here as ontogenetically immature and their bipedalism really just a mad dash towards the relative safety of the water as two Rugops have their eyes set on baby spino dinner. Because abelisaurids always seem to roam paleoart as duets - ever notice that? Cenomanian North Africa was not so much a large herbivore based ecology but a fish and fish eater based ecology. And Spinosaurus, especially the juveniles, potentially formed a large part of the prey base for the carcharodontosaurids and abelisaurids that - possibly to some extent - were temporally and environmentally coincident.

As the close-up here attests I put the little spino in a semi-contorted posture with the head and torso pulled back to bring the center of gravity closer to the hips. With each forward lunge the body is in danger of toppling forward as the larger individual in the mid-foreground is getting perilously close to doing so. But by pulling the torso and head back with each footfall at a rapid clip I can picture this locomotion working for the youngins. To help with balance the arms are splayed laterally like a tight-rope walkers balance pole.


I still maintain belly sliding takes care of that pesky center of gravity question and also allows them to negotiate the muddy/intertidal terrain they lived in. But the bipedal heritage of Spinosaurus can not be denied and I find it very probable that - like young/small crocodiles today - smaller spinos had much more liberty in terms of locomotory options on land than the more ponderous, gargantuan adults.



To take you into my minds' eye I think that they would somewhat resemble the quick bipedal sprint of basilisks (Jesus Christ lizards) and frilled lizards.



However some, or even many, of you reading this are not convinced of Ibrahim et al's proportions for Spinosaurus nor are you convinced that a novel adaptation such as some form of quadrupedalism or as I proposed belly sliding need be invoked for this animal(s). Consensus has been agnostic or equicocal concerning Ibrahim et al's proportions for Spinosaurus. Which leaves us in a funny place because renderings and depictions of Spinosaurus continue to come about and for the most part the professional paleoartists have gone into a sort of compromised position of depicting Spinosaurus having somewhat shorter legs than other theropods but still being a good ol' biped. The recent artwork depictions of Spinosaurus by Julius Csotonyi , Mark Witton, and Sergey Krasovsky all hedge their bets towards a longer in body, shorter legged, but still fundamentally bipedal Spinosaurus. I call this compromised sort of depiction of Spinosaurus the true "chimera" in all of this for reasons I will elaborate later.

To what extent was Spinosaurus bipedal? Most would say "we need more data", I say we have enough already to dismiss Spinosaurus as a less than ideal biped on land.  An anatomical incongruity has been rather summarily dismissed or just glossed over in discussions which I will highlight later. 

To me everything circles back to one fundamental question we should ask when settling on the interpretation of an animal: does this animal make sense as an evolutionarily successful animal in it's environment? Can it, in a reasonable manner do things like forage, move, mate, evade predators and in general get along in none too friendly environment full of obstacles, competitors, and predators? This notion that some animals from the fossil records are "in the process of adapting" or "an unfinished product" is bogus to me. Not only does such a sentiment smack of neo-Lamarckism but it also begs the question: where are all the unfinished products in today's biota? Is a mudskipper a less than perfect transitional species on its way to becoming terrestrial? No it's an animal doing just fine in the environment it lives in. Are gliding animals inferior to flying ones or are they better viewed as just good enough for where and how they live?

The jack of all trades, master of none interpretation of Spinosaurus as mixed forger of land and water is not congruent with the wealth of anatomical attributes pointing towards a primarily aquatic existence. The reluctance to give up obligate or classical theropodian terrestrial bipedalism - as evinced by the artistic depictions I mentioned earlier - is at odds with Spinosaurus' peculiar pelvic anatomy. There is a layer of evidence - sitting in plain sight as is so often the case - that speaks against "classic" theropod bipedalism. This anatomical incongruous - especially when viewed in light of the animal's likely habitat of complex, intertidal estuarine fluvial systems - essentially creates a vanishingly small window of opportunity for the bipedal loyalists to maintain Spinosaurus as just another good ol' bipedal theropod. 



You may or may not recall that paleo-super hunk and Papa John spokesman Paul Sereno starred in a very well done promotional video that coincided with the infamous Spinosaurus Science publication. In this video Paul offers some really great and captivating sound bites and a little background on this most fabled of dinosaurs. For our purposes here he makes special emphasis on the femur of FSAC-KK-11888:

On lacking a marrow cavity: "It didn't have a marrow cavity. We had never seen this in any predatory dinosaur. they all have good marrow cavities. And that resembles animals that are actually spending a lot of time in the water. They want to be a little heavier than the water so they don't float all the time and they can control their swimming movements."



On the proportion of the thigh bone (femur) vs shin bone (tibia): "This thigh bone is shorter than the shinbone by several inches.... In animals that are sitting on top of the water and using their limb to paddle that thigh bone becomes short and stocky."



On the caudemofemoralis attachment "On that thigh bone we noticed that the attachment for the muscle that moves it back is huge. So what were looking at is an animal that has adapted it's hindlimb largely for paddling in water."

A couple of things here. While it's old hat that Spinosaurus lacked a marrow cavity I want to point out an inconsistency in Paul's thinking. In one instance he asserts that such animal's want to be a "little heavier than the water so that they don't float all the time" and to "control their swimming movements". This makes sense and I mostly agree with what he is saying here. But then later on Paul - when talking about the use of the hind limb and it's expanded musculature to paddle through the water contradicts himself saying, "In animals that are sitting on top of the water and using their limb to paddle that thigh bone becomes short and stocky".

Did you catch that? We can't have it both ways - Spinosaurus is either a floater or sinker. It's either heavier than the water (a sinker) or lighter than the water (a floater). In order for Spinosaurus to be a floating paddler like a duck or seagull we would not expect such dense bones. Spinosaurus is therefore - as I have been arguing for a while now - a sinker and when dense bones are combined with a dense dermis, which is not unparalleled,  it is more tenable to interpret Spinosaurus as an animal that sinks right down to the bottom. Which is where the true nature of Spinosaurus' unique and powerful pelvic anatomy come to fruition as an underwater walker.

Before I go into how and why Spinosaurus was such a superbly and beautifully adapted underwater walker one final nail in the coffin of this notion of Spinosaurus as floating paddler. Surface area. One of the most important concepts in paleo - functional analysis is the square-cube law.  As an animal increases in size the volume (read bulk) increases at a much higher rate than the surface area. Therefore a structure that is dependent on surface area to do it's job efficiently - such as a paddle - must hold pat and increase at a concurrent rate as size increases. In other words a 5 ton duck should have relatively larger paddles than a 2 lb duck. Like crazy huge paddles. Spinosaurs is a big, heavy and long animal. Even the most rudimentary, intuitive spitball analysis looking at it's paddling arsenal shows that it does not really have the type and spread of foot paddle needed to even move at the relative speed of a duck on the top of the water - much less the type of speed needed for a predator that, you know, had to go out and catch stuff. Just check out the huge rear foot paddles on a true rear foot paddler in the beaver pictured below.

Beaver on bank lower Kern River. credit Ryanx7. CC3.0

"The pelvic girdle and hind limb are considerably reduced in Spinosaurus. The surface area of the iliac blade is approximately one-half that in most theropods, and the supracetabular crest that supports the hind limb is low."

This is a crucial point that the bipedal loyalists have seemingly glossed over. The musculature and skeletal framework that are exactly crucial for standing bipedally (on terra firma) are diminished in Spinosaurus. Not only are the legs proportionately smaller in FSAC-KK-11888 (the proposed neotype) but the legs are relatively diminished in their capacity to support and maintain bipedality.

From Ibrahim et al.:

"The femur in Spinosaurus has an unusually robust attachment for the caudofemoral musculature, which is anchored along nearly one-third of the femoral shaft, suggesting powerful posterior flexion of the hind limb. The articulation at the knee joint for vertical limb support, in contrast, is reduced. The distal condyles of the femur are narrow, and the cnemial crest of the tibia is only moderately expanded."

What we have here in FSAC-KK-11888 is an incongruity that needs explaining. On one hand the femur and musculature attached give us a signal for massive power in the horizontal plane. Discordant with this observation is the relatively weak and diminished musculature and skeletal structure for the vertical plane that would be needed to support a biped of this size. How to explain this seeming contradiction?

Let's revisit my contention earlier than an animal should work reasonably well in it's environment. If we put Spinosaurus in the large, complex mangrove/deltaic/intertidal habitat that is most likely for it and infer bipedalism we should expect the opposite pattern of limb development. That is, far from being diminished in size, the skeletal and muscular framework for bipedalism should be hypertrophied (larger & stronger). The reason is that pushing yourself through water, mud, thick sand, tangles of mangrove vegetation as a biped is hard work. So if Spinosaurus was indeed doing this as an obligate biped we should see greatly expanded musculature for bipedalism in terms of vertical support, which we don't.  I cite the remarkable robusticity and upper muscular development for the swamp lions of Botswana's Okavango delta. These impressive lions - the females of which are as big as male lions elsewhere - have expanded chest and shoulder musculature that assist in not only their main prey - Cape buffalo - but also in swimming, wading, and pushing through their swampy, flooded habitat. There is even some suggestion of a separate subspecies emerging.


So using simple deduction if we can eliminate paddling as a way to explain Spinosaurus' pelvic anatomy on the grounds that it simply did not have too great of a surface area for foot paddling and if we can eliminate terrestrial walking/wading on the grounds that the exact structures needed for such an adaptation are diminished in Spinosaurus - the exact opposite of what should occur in such a large biped in a swamp - then we are left with underwater walking or "punting".

Underwater walking is consistent with the dense bones, diminished size of pelvic area, and greatly expanded caudemofemoral attachment. Neither obligate bipedalism nor paddling addresses the unique and seemingly incongruous features in Spinosaurus. Furthermore the lack of vertical support at the knee joint as noted in the Ibrahim's et al. paper speaks against both bipedalism and quadrupedalism and is another line of evidence in support of belly sliding. Even if Spinosaurus were to have evolved some form of quadrupedalism there is no reason for such an adaptation to cause a decrease in the ability of the hindlimbs to hold weight.



Finally those puny legs - a seeming weakness - are actually superior to long legs for an underwater walker. In one of the few research papers that actually attempted to quantify and bring some discourse to the manner in which hippo run underwater it was found that short, quick steps or "punts" actually outpace the longer "gliding" paces in speed when measured in controlled observations of hippos walking underwater.

Comparing hippo locomotion underwater to humans moving in a "microgravity" environment (i.e. outer space) Coughlin & Fish wrote in their abstract:

"Ground contact time decreased with increasing horizontal velocity,"

Which translates to as the hippo moved faster underwater the amount of time that the foot hit the ground decreased.

"vertical displacement during the unsupported intervals increased with an increase in ground contact time,"

"vertical displacement" refers to how high the hippo rises off the bottom of the tank in their observations. Since longer ground contact time is associated with slower relative speed when the hippo is moving relatively slowly its foot contacts the ground longer and it rises higher in the water column (i.e. gliding phases).

"and time between consecutive footfalls decreased with an increase in horizontal velocity."

which is pretty straightforward - as the hippo increased in velocity footfalls became more frequent (but still relatively short in duration).



Spinosaurus likely had the same pattern of locomotion underwater. Slow speeds with increased foot contact time and longer gliding phases (how beautiful to imagine btw). Higher speeds had decreased foot contact time and shorter unsupported intervals. Some might poo-poo this line of reasoning "you can't compare a bipedal dinosaur to a quadrupedal mammal blah, blah" but much recent work has highlighted congruity in all forms of tetrapod locomotion - especially remarkable convergence in aquatic locomotion in tetrapods. Furthermore you can test it out yourself as a biped. Go to a pool or body of water up to your chest and run. You will quickly see that short, quick steps with little gliding phase outpaces longer paces with lengthier gliding phases. As the authors note in the paper: "Under conditions of microgravity, humans switch from a walk to a run at slower speeds. (Kram et al, 1997)"

And don't for a second dismiss underwater walking or "punting" as a less efficient or even speedy way of moving through water than swimming. Check out the speed and alacrity in which the hippos in this  clip move. Although you can not see them as the people are in a boat - you can surmise from the wake and relative speed of the boat that the animals are moving along underwater at quite a pace.



The short and powerful legs of Spinosaurus are therefore beneficial to walking underwater at speed since short and quick paces outperform long paces for underwater walking.

In the discussion from the hippo/microgravity paper the authors also highlight the importance of the animal in question being denser than the water,

"Effective bottom walking requires a body that is denser than water when submerged."

As I argued in my first post in this series on Spino there is reason to make Spinosaurus denser than the water via dense bones and an extensive and dense epidermis not without parrallel to manatees, hippos, and possibly tapirs.

When we put Spinosaurus in it's proper environmental context which is completely underwater - not some bastardized giant heron nor an improbable jack of all trades switch-hitter of surf and turf - now a real functional use for the sail emerges. As I discussed in my last post the sail would not sit above water anyways as the display marker so many have championed, nor would it add any sort of propulsive power either. But what it would do, I suggest, is act as stabilizer - a dorsal keel - that helped prevent Spinosaurus from rolling when twisting and turning underwater. As much as I have championed the hippo as a useful model for Spinosaurus underwater movement, they differ in one fundamental aspect. Hippos do not have to move with much agility underwater because their primary food - grass - does not grow there nor would it swim away from them if it did. Spinosaurus as an underwater hunter of aquatic prey that did not want to get caught - needs relatively more agility underwater than a hippo. Additionally, because Spinosaurus moves as an underwater bipedal walker not a quadruped, if Spinosaurus changes course rapidly underwater and it's body starts rolling it has no way to correct itself with forelimbs (like a hippo). Now caught in an underwater body roll a Spinosaurus'hind limbs would lose contact with the substrate and it would lose it's main propulsive power since pushing off the substrate is required in underwater punting. A sail helps with this dilemma so that as Spinosaurus twists and turns underwater to either sides the sail pushes back against the water and helps prevent rolling.



Ha, ha I made Spino almost comically "fat" but really no more ponderous that a hippo. You will note that I actually depicted another, more subtle, use for the sail in the top pic. That due to it's swayback morophology the sail may have hydro dynamically made movement underwater more efficient. As the animal moves from right to left, as shown by the large arrow - water flows up and over the sail but forms little micro-eddies over each rise and fall of the sail. The effect is that a slipstream develops that allows Spinosaurus to recoup some of the energy dispensed moving through the water. If you think about the way competitive bicyclists use slipstreams or even the "shake and bake" tactic used in competitive race car events this is not far from what I am suggesting. In the biological realm birds flying in formation or even migrating lobsters moving in line take advantage of the energy saving features of slipstreams. Spinosaurus may have done the same with it's sail underwater in addition to it's movement stabilizing attributes and not altogether dismissing possible uses for bluff/intimidation/social signalling, thermodynamics, prey corral, buoyancy control, and mineral storage.

Oh yeah I almost forgot. What animal also has big flat unguals and partially webbed toes? Take a wild guess...

Ibrahim et al 2014

Also it is worth repeating how "barrel chested"Spinosaurus really is. This is an important point and another nick against trying to retrieve any meaningful terrestrial bipedality. The front of this animal was heavy. Furthermore it compares very well with the skeletal framework of - you guessed it - a hippo. Drape on some muscle, meat, and a thick skin and you will have a very voluptuous - and long - animal. The likes of which is going to be very maladapted for bipedal movement on land and even worse off trying to walk through thick tidal muds, sands, and tangles of swamp vegetation.

link Youtube Hippo 3d skeleton

In the water it was a superbly adapted underwater bipedal walker or "punter" - very graceful, powerful and daunting in that environment. On land, not so much. Smaller juveniles could have enjoyed more liberty in moving around terrestrially, perhaps even going into quick bipedal sprints. As I have maintained since before the actual publication of the Ibrahim material it was a belly sliding mud surfer, looking like an amalgamation of a giant saltwater croc, a penguin, and a loon.  But that was ok for what it had to do in life. It conceded terrestrial ability for aquatic proficiency. And that is not radical or revolutionary or even unique - every tetrapod lineage that transitions back into the aquatic realm concedes some or even all amount of terrestrial capability. Otters, beavers, crocodiles, pinnipeds, loons, penguins they all can move around on land but are much less proficient on land than their related terrestrial brethren.

CC 2.0 credit Mike Bowler. Spinosaurus & Onchoprostis

Well for now that about does it for all I want to say on Spinosaurus (although things always change). I am quite confident that my take on Spinosaurus - a belly sliding, underwater punting, primarily aquatic/piscivorous beast of tidal waterways - will prove to have much truthiness to it.

And in closing I leave you with a depiction of an adult Spinosaurus closing off a tidal outlet and using it's length, size and sail to corral aquatic animals trying to exit with the outgoing tide. The experienced adult has enmeshed itself between two thickets of the mangrove fern Weishchelia reticulataand completely dammed off the outflow channel from a tidal mudflat that fish came up through to feed during high tide. Contrary to the vast majority of Spinosaurus/ Kem-Kem paleoart which feature towering cypress canopy relatively low and shrubby cheirolepidiacean conifers and Weischelia should dominate the flora. Some of the fish - Lepidotes - even swim out of the water to escape the hungry maw of the Spinosaurus while other fish such as the sawshark and various sarcopterygians attempt to vault over the striking theropod to get to the deeper safer water on the other side. I would suggest that this form of fishing - not too dissimilar to what modern crocs do - would be a very efficient and likely manner of fishing for Spinosaurus especially amongst the older, larger, and more experienced Spinos that knew how to take advantage of such tidal choke points. A chunk has also been taken out of the Spino's sail. Also take note of the pterosaurs and dromaeosaurids attracted to the commotion and easy feed provided by the spino.

Tidal Harbinger Negative Brown by Duane Nash click image for larger view

Tidal Harbinger Shocked Pink by Duane Nash click image for larger view

I have actually amassed quite a lot of posts on Spinosaurus going back nearly to the start of this blog. Going back and reading these may be of interest to see the evolution of my ideas - including ideas I have since abandoned.

Spinosaurus Unauthorized II: Spino Identity Crisis & Island Hopping Hipposfrom November 2, 2015 in which I go into Sigillmassasaurus and what this animal means and does not mean for the "new"Spinosaurus and highlight a pivotal point generally overlooked in discussion of the veracity of FSAC-KK-11888. More on hippos and what island hopping hippos tell us and don't tell us about swimming ability and lack there of.

Spinosaurus Unauthorized I: Hippos Are Not Really Fat and Can't Swimfrom October 12, 2015. I return to the spino debacle and begin building my case that Spinosaurus works most effectively as an underwater walker/punter. In order to do so I have to spend a lot of time on hippos and a whole lot of effort arguing that hippos can not actually swim. I also argue that Spinosaurus sported a very thick and heavy dermis that assisted as ballast control along with the thick bones similar to manatees, hippos, tapirs, and walrus.

Time For the Giant Heron Spinosaurid Analogy to Bite the Dust Part 2: Getting More Than Just Your Feet Wetfrom November 7, 2014 in which I elaborate on why the heron/spinosaur comparison is very much less than ideal and not at all the best of all candidate analogs. Also why depictions of spinosaurids  standing on the edge of riverbanks hoping for big fist to blunder on by is patently ridiculous.

Time For the Giant Heron Spinosaurid Analogy to Bite the Dust Part Ifrom November 2, 2014. In which Thomas Holtz says I make a straw man argument.

"Last Man Standing... el Ultimo Hombre": As the Dust Settles on the Spinosaurus BombshellfromSeptember 14, 2014. Well the dust is still settling and well, sometimes you have to push the issue to get people to take notice.

Adding Some Context to the Middle Eastern Attack Today. from September 11, 2014. Do you see what I did there? Very meta.

Surf OR Turf: Can a Terrestrial/Aquatic Switch Hitter Really Exist?from August 31, 2014. Skeptical of the notion that Spinosaurus ala JP3 could function equally proficiently in the water or land.

Did Bakker Get Spinosaurus Right After All?from August 16, 2014 in which - upon seeing the leaked Nat Geo photos of the new Spino reconstruction - first mused that Bakker got Spinosaurus right in the animal being very aquatic and where I first argue the belly sliding hypothesis. I am now equivocal on how much the forelimbs - if at all - assisted in belly sliding or a "combat crawl" type of movement or some combination there of. In either case the post is one of my most popular and still gets lots of links and hits never mind the fact that I feel how Spino moved terrestrially is among the least interesting aspects of the animal.

Planet Predator II: Kem Kemfrom September 7, 2012 in which I muse on the ecology of the Kem Kem & Cenomanian North Africa and Spinosaurus' place in the ecosystem as prey, competitor, and provider of fish dinners for other kleptoparasitic theropods.



References

Coughlin, Brittany & Frank, E.  Hippopotamus underwater locomotion: reduced gravity movements for a massive mammal. (2009) Journal of Mammalogy 90(3) 675-679

You may have already heard the chatterings, mumblings, and rumors spread hither and thither. In the smoky backroom chatboards, comments sections, forums, and discussion threads a growing disquiet over a certain very real - but also mytho-cultural - beast. To those attuned to the dinosaur blogosphere internet meta-brain this notion should be none too radical but to those uninitiated the notion is simple and revelatory at the same time: we might just be getting Tyrannosaurus rex totally wrong as goes appearance, especially in the face. T. rex might look just plain silly, or weird, or altogether more surreal than what we have built it up to look like.



Tyrannosaurus rex - as both a scientific and cultural phenomena - is imbued with both values as goes it's appearance. And humans - as culturally adapted critters - try as we might can not decouple the two as stringently as we might hope in reconstructing this beast.

This post is going to be necessarily both a cultural and scientific deconstruction of Tyrannosaurus rex facial appearance focusing on two main aspects. As such we must wear both a cultural and scientific hat here in an attempt to de-clutter and re-imagine a creature undeniably real but also imbued to an obscene degree by cultural baggage, gender notions, and aesthetics. This treatment will also hold implications for many other extinct theropods to greater or lesser degrees. Where you fall down in the end as goes appearance - will be a blend of science, aesthetics, and culture - which is as how it has always been with these guys (i.e. extinct animal restoration).

The beginning (and really the end as well we shall see) of T. rex facial reconstruction must really start at ground zero - the skull. Just take a second to breath it all in... it really is structurally and aesthetically a work of art and powerfully built symmetry.

AMNH 5027, A.E. Anderson Public Domain

Now as appealing as this bony synthesis of power and grace is we must concede that the bony appearance of an animal's skeletons is often times not a direct reflection of an animal's outer appearance. In T. rex the skull's beautiful, symmetric, and aesthetically pleasing appearance may have a lot more to do with being influenced by a uniquely and profoundly strong set of muscles than it being a true reading of it's life appearance. T. rex has  evolved to deliver crushing bites and sustain stresses in multiple force vectors. It is built to give and take a licking and keep on ticking.

But just take a second to bathe in the below photos...

Red Tegu photos credit from Helen Zhu.

The above x-rays (borrowed from Helen Zhu's research page) should give you moment to pause and reflect upon how much soft tissue can surround and obscure even a reptiles skull (diapsids generally being impoverished in facial muscles compared to mammals). It should be noted that huge jowls of the red tegu are a male feature and are mainly for show although the huge pterygoideus muscles certainly help with cracking snails and shellfish - a common part of the animal's diet.


As the above youtuber puts it these prominent muscles in the tegu form some very voluptuous "neck boobs" on the side of the jaw. Crocodiles also feature said neck boobs that form the dominant jaw closing group of muscles in their particular jaw apparatus (they don't put a lot of muscles on the top of the head for concealment reasons).

Now to what extent and how much T. rex, and other tyrant lizards - or even theropods in general had prominent pterygoideus muscles is equivocal and loaded with uncertainty as is the muscular reconstruction of any extinct animal. But as one of the largest and in fact the strongest biting terrestrial vertebrate T. rex likely had some rather prominent "neck boobs", at least more so than is almost always depicted.

Here are some pics on how the pterygoideus muscles may have attached in T. rex and Majungasaurus:

Pterygoideus group in purple (from Bates & Falkingham, 2012)

Pterygoideus muscles = mPTv from C.M Holliday 2009

credit Ira Block/ model Brain Cooley

Again this post is not so much about the bite force and the technical side of theropod / T. rex biting but appearance and the cultural conceits there of. So whether or not T. rex had red tegu sized "neck boobs" or maybe something like a croc or somewhat less than that - there is a lot of room for variation in how much "neck boob" you want to put on your T. rex as well as other theropods. But do we see this variation in T. rex paleoart? I can say almost universally nope, no we don't. Go peruse T. rex art and you will see that the pterygoideus is petite at best and sometimes not even there.

One avenue of looking into how much muscle T. rex was packing there is to compare the size of this muscle in juvenile versus adult crocodilians. As is seen in these dissections of immature crocs the size of the pterygoideus is fairly modest in relation to the animal's whole head. This changes with adulthood when we the grotesquely flared pterygoideus of large crocs.

If we peruse this nice color schematic of the jaw closing muscles of the American alligator (Alligator mississippiensis) it is obviously that it is a youngster (big eyes) and it does not have quite the degree of pterygoideus flare or "neck boob" as the boomer sized adults have. From Holliday et al 2013 Plos One A 3D Interactive Model and Atlas of the Jaw Closing Musculature of Alligator mississippiensis)

credit Holliday et al 2013 pterygoideus in orange/red

Note prominent jaw muscle "neck boobs" CC2.0 credit fvanrenterghem

Now compare the muscles in a large croc to a baby croc:

Getty Images

Is this ontogenetic change due to a shift from small prey to large prey? I don't know if that is completely the answer... in fact I am not sure that adult crocs prey on animals any larger relative to their own size than baby crocs. I suspect it has a lot more to do with the ol' square cube law. As crocs get bigger their volume increases disproportionate to their surface area. Muscles have volume but they are also influenced a lot by surface area. Big crocs have to move a lot more mass (i.e. from having more volume) relative to small crocs and grow muscles disproportionately larger than small crocs to basically do the same job - bite and subdue prey. There is probably a paper or two in there somewhere but I don't know if it has been written.

Following from this maybe... just maybe... T. rex had to grow some quite impressive jaw closing pterygoideus muscles to do it's job amply - after all it was certainly no light weight.

Again my main point in all of this is not to convince you one way or the other if T. rex had red tegu sized neck boobs or something more moderate. Chances are it had something prominent there and given it's size and proclivity for a particularly strong, tenacious, and evenly distributed bite the pterygoideus would and should be apparent in life.

But do restorations give this muscle enough flare, weight, and voluptuous girth? I would say no and the  reason I think it is underrepresented I suggest is cultural.

We have all been smitten, bedazzled, and suffered a bit of a man-crush on T. rex's hypermasculine and all too handsome jawline.

You heard me right, the jaw line of T. rex features a jaw line that any A-list Hollywood actor would kill for. The human male jawline is a perhaps seldom mentioned but very distinctive and sought after trait in male sex symbols and is also ubiquitous across... hypermasculine male superheroes.

Pixaby

credit Elaine Thompson AP

We are drawn to Tyrannosaurus rex - possibly on a subconscious level - because the skull encapsulates many of the male attributes we find desirable in our own species both sexually and for our leaders, warriors, and mythical superheroes.


And I did not even mention the strong chin of T. rex which adds a whole other layer to the hypermasculine attributes we are drawn to in the T. rex skull.

John Gurches now iconic T. rex. Note prominent chin and jawline well displayed. Archetypal hero stance

But what if the strong jawline of T. rex - seemingly chiseled out of tooth, scale, and hypermasculine hero worship - was cloaked by layers of feather, flaps of skin, or as suggested earlier in the post by particularly voluptuous "neck boobs" and jowels giving the animal a decidedly softer, rounder and perhaps feminized appearance? Things could change a lot as goes appearance. The skull of T. rex is optimized for muscular performance, not to appeal to the cultural and sexual biases of extant hominins.

Astute readers should note that this cultural and anatomical analysis of T. rex appearance has implications for how other theropods are restored to greater or lesser extents it is just easier to make the point with big ol' sexy rexy.

For the next part of my analysis I want to talk about a soft tissue that regular readers of the dino-blogosphere should be well aware of and which is quite possibly one of the most contentious issues in theropod soft tissue restoration: lips. Yep, I am going into lips.

Instead of making a long and lengthy review of this issue I am going to outsource some of the background as the issue has of course been gone over extensively by Jaime Headden - Making Lip of It, Support For a Lipless, Cheekless Dinosaur World, Cheeky Commentary on Ornithischians& others

To summarize my views going in and add some arguments that probably need reiteration:

Theropods most likely had lips. I also think that these lips (contra most depictions including my own) would have mostly or even completely covered the teeth. While the notion of a croc like skin sheathing the head of theropods has been argued, probably most vociferously by Tracy Ford, what I find lacking is that fully exposed teeth and oral cavity would put a lot of burden on the animal in terms of water loss via exhalation. Here it is worth noting that terrestrial predators keep a pretty tight seal on the mouth. Aquatic animals, not so much - sharks and crocs come to mind but there are many more examples of exposed snaggle toothed aquatic animals. There definitely seems to be a bit of bias for aquatic animals having more exposed oral regions than terrestrial.

One of the critiques for lower lips in theropods is that the preserved skulls for many theropods suggest that the upper teeth would penetrate into the lower lips and gums of said animals cutting such features to shreds. Check these pics out. However one of the best rebuttals to this argument was done by Tyler Keillor in the chapter Jane in the Flesh: The State of Life-Reconstruction in Paleoart from the excellent book Tyrannosaurid Paleobiology. Let me quote Keillor directly as I don't know if this argument gets enough exposure:

What's my name? extreme jaw closure credit James St. John CC2.0

On Jaw Closure (pp 160-161):

"...fossilized theropod skulls have been found with the jaws tightly closed. While some artists have used this as the living animal's closed-mouth pose, I offer another interpretation. The jaws that are tightly clenched may show a postmortem deformation, akin to the "death curve" seen in the axial columns of many vertebrates under certain conditions. As tissues desiccated and shrank in the dead animal, the massive jaw closing muscles may have shortened and pulled the jaw tightly closed, more so than it would have been in life. Punctures in the palate of Sue occurred after death, when the jaw's dentary teeth were closed further than they had been in life (Brochu 2003). In skulls that are preserved right-side up and resting on their jaws, overlying sediment compaction after burial could further crush the jaws closed in dorsoventral compression (Bakker et al. 1988)"

I would actually go a little further than Bakker and suggest that irregardless of whether the skull is preserved right side up compression from multiple angles could compress the jaw shut. Why? Because the earth shifts and moves all the time not just from top to bottom.

Furthermore Keillor draws attention to a rather simple and seldom mentioned critique of the "extreme close mouthed" interpretation which is bone on bone contact with no room for soft tissue. When a skull was put in this pose (extreme close mouthed) Keillor noted "contact between the quadrate and angular, the jugal and extopterygoid come close to touching the surangular, and the dentary teeth contact the palatal bones and medial maxillae (pp 162)".

Keillor also decides that in the situation of tyrannosaur lips he must look beyond the extant phylogenetic bracket of modern birds and crocs due to their unique specializations (beaked and aquatic)  not offering the ideal evolutionary context for a toothed terrestrial predator. And here I agree the EPB feels a little lacking. Keillor expands the bracket to consider large terrestrial predatory lizards i.e. the komodo dragon as the ideal model for looking at the type of "lippy" tissue present and the ideal neutral position of jaw closure. Essentially this lizard lip type arrangement allows a tight seal when closed - to enhance "sniffing" presumably - as well as protect the oral cavity and teeth from dehydration and abrasion. Yeah it is kind of a "just so" argument but keeping your cutlery sheathed and moist probably has some fairly obvious benefits to it in drying terrestrial environs full of abrasives.

Probably one of the best representative views of the lizard lips hypothesis is that done by the promising game Saurian. Picture below borrowed from said development team:

credit Saurian development team

You should note that when the mouth is open the upper teeth have nice little "pockets" to fit into between the dentary and outer lower lip. When the jaw is shut the lips seal things up nice and flush to create a tight seal that inhibits moisture loss and enhance the ability to suck up smells via the nose.

That the upper teeth went below and lateral to the dentary is corroborated by the path the nutrient foramen follow on the dentary.

Below one of my favorite skeletal mounts of T. rex because it eschews the overdone Rex vs Triceratops battle. You can see quite clearly how the nutrient foramen on the upper jaw come right to the edge of the alveolar margin on the upper jaw (maxillae). But if you trace the path of the nutrient foramen on the bottom jaw (dentary) you will notice that while the nutrient foramen come up against the edge of the teeth in the anterior and posterior they take a noticeable dip towards the middle of the jaw - which corresponds directly with where the longest teeth from the upper jaw would be presumably in closure.

Houston Museum of Natural History. credit Daderot CC. Edmontonia & Wyrex

note how nutrient foramen take a dip along bottom margin of jaw corresponding to longest upper teeth

So all is hunky dory right? T. rex - and probably most predatory theropods - had lizard lips fairly similar to monitor lizards like komodo dragons right?

Not so fast Mr. Lizard Lips...

To prime you for my argument please take a good long hard look at another readily available wiki pic of ol' sexy rexy that is taken from the front. If you look into its orbits and squint just a bit you will see it....

credit ScottRobertAnselmo CC3.0 "Sue"

There are some (blasphemy!!) very mammalian things going on here...  those endearing forward facing eyes looking right into your soul... then there is the VERY prominent nasal region (smell being a noted mammalian sense)... that pinched in upper snout which allows the binocular vision... which itself creates a sort of "muzzle"... which terminates in some heterodont dentition with vaguely "incisiform" front teeth for nipping and the tallest but still very stout and almost caniform teeth midway back on the upper jaws... and that flared back of the skull creating a vaguely cheeky countenance. Not only are we attracted to ol' sexy rexy for it's ruggedly handsome jawline but, well, to put it frankly it is harkening up some distinctively mammal type sentiments in us that remind us vaguely of the mammal things we are ourselves and which we allow most intimately in our homes and lives.

Cave Bear. wiki commons

Furthermore when we look at terrestrial predators that share these same attributes of heterodont dentition, binocular vision, a dominant olfactory sensory apparatus - they don't have lizard lips, they have loose, draping, jowel like lips. Yes I am looking at canids, ursids, hyaenids, and even felids to an extent. And yes I took the liberty of extending the bracket further than reptiles to include these predators that might offer more utility than a lizard. Because really what we are talking about is simply growing more skin and all kinds of animals grow all types of skin so again here I don't think the EPB offers much utility. I can see why people are more comfortable with the lizard lips hypothesis for T. rex it might feel safer than what I am offering. But let's break that somewhat arbitrary rule and see where it takes us...



To clarify I should stipulate that I am not suggesting we consider muscular mammal style lips in T. rex and other theropods but basically loose and hangy jowls of flesh (think condor cheeks but not continuous across mouth).
What is lacking in the lips debate is really any type of analysis comparing the adaptive benefits of tight sealing lizard type lips versus the more open hanging mammalian style lips. That debate has not occurred because, well to put it bluntly, mammal type "bulldog" like lips in T. rex and other theropods has been shut down by not being talked about at all really. These are the assertions that essentially shut down the topic I hear and feel free to illuminate me if there are more rigorous reasons not to consider bulldog lips in the comments section btw.

"Too far outside the phylogenetic bracket" 

- Well when we infer lizard lips we are already outside the phylogenetic bracket... so.... and it is a bit telling that many seem to have no problem inferring fleshy mammalian (albeit non-muscular) cheeks in ornithischians but how do dare you consider fleshy, hangy lips in a theropod!!

Or my favorite: "I find them unlikely"

- Like that is all you have to say on bulldog style lips to not consider them? No support at all for not considering, just saying "unlikely"...

I suspect that there is more to it than this and people don't want to consider bulldog style lips because well... aesthetically and culturally it is not what we might like or even feel comfortable with on theropods and especially ol' sexy rexy. Because as I have been saying all along these are as much cultural creations as they are objective scientific animals. Both academics and fans of theropods and T. rex have ignored the idea of hangy, floppy lips in these animals because... for the most part they just seem to laugh and ridicule the idea away.

So as opposed to trying to decipher the type and extent of "lip" in these animals via skeletal traces which I think is a proposal loaded with potential pitfalls - for example how do you account for the amount of stem cells that might just grow loads of skin and tissue (?) - I am going to take another line of inference. I will be exploring lizard lips versus jowl style hanging bulldog lips in terms of relative adaptive benefit. This is admittedly not going to seal the deal either way because there is some subjectivity involved as well as the fact that animals don't always evolve into "optimal" or "perfect" organisms. However I do think comparing the relative benefits of either style of lip in lieu of really being able to eliminate either possibility is a valid form of inquiry. Again it might not seal the deal but it may open up some minds to possibilities...

The Smell Situation

There is one important distinction between lizards and theropods/mammals. Lizards primarily scent the world via their Jacobson's organ - the vomeronasal organ. In all lizards and snakes this organ is present and in reptiles that scent their prey the distinctive fork tongue is the tool that is used to gather sensory input from the environment and put into contact with the vomeronasal organ. Lizards and snakes - because of this system of sensory input don't need loose lips to let information from the environment into their oral cavity because their forked tongue does all the work for them. For lizards and snakes having loose lips to let chemical cues into the oral region is redundant and an unnecessary potential source of water loss. It is true that certain mammals have this organ but in general it is substantially reduced compared to reptiles. I can find no reference to this organ in birds and crocs and it is likely absent or extremely reduced in dinosaurs.

However, as anyone who has had or watched a baby explore its environment via its mouth can attest,  having a relatively open and exploratory labial region may carry significant adaptive advantage. Animals can taste things and loose lips that can be pressed into various substrates can help pick up and adhere odors that can then be picked up by the nose or tasted. Having loose jowl type lips in this scenario of helping to scent or taste things would hold substantial adaptive advantage over the tight sealing lizard lips associated with reptiles that explore the world via their fork tongue.

The bloodhound dog breed - a specialized scenting breed of dog - has low hanging ears that trail along the ground, loads of wrinkles on the face, dewlaps, and very prominent jowls. All of these features have been suggested to stir up, trap, store, and distribute sensory cues for the nose.

Bloodhound. credit Superfantastic CC2.0

It is not unreasonable to argue such adaptive benefits to various theropods - especially T. rex - in scenting and tracking food, rivals, mates etc etc. The open jowls and additional sticky substrate exposed to the environment  would help trap and collect scents in close proximity to the nose. Certainly a lot more potential adaptive benefits in these regards than thin closed lizard lips.

Hellhound Rex by Duane Nash

Tactile Input, Prey Handling & Delicate Nipping

Another benefit of having more open "bulldog" style lips versus closed lizard type lips is the potentially higher amount of sensory data collection points available to "feel out" things. This ability comes in handy in terms of how to react and fine tune grip/bite strength/position when engaged with struggling prey. Having lips that can sense and anticipate muscular twitches of struggling prey is a great advantage to have as it allows the predator to fine tune its own biting and avoid suffering undue injury. Lizard lips, exposing much less sensory surface area than bulldog type lips, offer less data collection points to make these rapid adjustments. Again, adaptive advantage goes to the bulldog lips.

I know that there is something about cats I should be saying here I read somewhere. That when biting struggling prey the sensitive lips and whiskers are able to detect and collect information on the prey. Ok found something I can give to you from The Other Saber-tooths: Scimitar tooth Cats of the Western Hemisphere:

from pp.26:

"large scale movement of the prey relative to the predator can be constrained by powerful forearms, but fine scale adjustments in upper canine placement require tactile input from whiskers, lips, and nerves in the periodontal ligament and pulp cavity." 

Granted T. rex was probably not making the precise bite adjustments of a felid but still could be of use.

The "incisiform" front dentition which allows delicate scraping of meat off of bones is also potentially aided by exposed and extensive lippage. Having a bit of a blind spot here and lacking sensory tactile front paws T. rex could feel out where the trace bits of meat are on a bone and better position its incisors for delicate nipping. Thin and not too supple lizard lips would be less efficient in these regards. Or whiskers...

Take home point: precise biting/nipping with heterodont dentition is associated with loose lips in extant animals and not lizard lips.

Teeth Baring




Although humans have bastardized this traditionally violent signal of aggression into something called a smile the ability to bare your teeth in a visible threat display is a potent and well understood universal across the animal kingdom. The lizard lip model might allow the teeth to show a little bit and maybe not at all in some theropods but in the bulldog lip model the upper teeth are potentially totally obscured ( I doubt that they had facial muscles to enact a sneer) but the bottom teeth and gums would be totally exposed when the theropod opened its mouth just slightly, creating a startling and disturbing visage of exposed gums and teeth. Once again, adaptive advantage goes to the bulldog lips.



Water Loss

Now you would thing that the tight fitting lizard lips would hold a substantial advantage over the more loose and draping habit of bulldog lips there might be more than meets the eye. Mucous could be particularly viscous inhibiting loss. The gap between the lower two mandibles forms a natural trough so that saliva would not be spilling out at a high rate anyways. And camels. Yes camels. If there was ever any animal that should be outfitted for water conversation among mammalia it is camels. Yet camels are noted for having particularly loose and jowly lips. And also, not coincidentally I suspect, camels are noted for a particularly good sense of smell. So whatever evolutionary disadvantages are incumbent upon having a loose set of lips in the dry desert they are not profound enough for camels to evolve a tight set of lips - or at least tighter fitting than the pics below attest.

credit AP

Tight Seal For Sniffing

Sort of a toss up. Reptiles with tight fitting lizard lips should get a pretty tight seal that will enhance sniffing. You would think that the more loose and drapey lips of mammal sniffers would be inferior but it does not seem to stymy them much as they seem to be doing just fine in terms of olfactory prowess. I don't see why such an arrangement in theropods would not work as well for sniffing.

Probably a mention of an extensive secondary palate in T. rex is worth mentioning here...

On a related note I did some research viewing of how bears - the penultimate scenters - actually do their sniffing. What I found was surprising and interesting and I don't know if it has been explored further. What I noticed is that sometimes when a bear is intently sniffing it will repeatedly open and close its mouth. Is it trying to taste the air? Or is it trying to suck air in closer to the nose by opening and closing it's mouth creating a vacuum. Check it out:


Check out the same sniff then open and close mouth behavior in this video as well:


And this brown bear does it too:


Anyways if the bears in these videos are trying to draw air into and closer to the nose I can easily imagine a T. rex doing a similar sort of behavior. Or maybe this behavior has something to do with a (reduced) Jacobson's organ?

Another interesting bear fact I learned in making this is that the lips of bears - apart from all other carnivorans - do not attach directly to the gums. Presumably this is to allow fine tune manipulation of small objects - such as plucking a single berry off a bush. Interesting to think how omnivory and the quest for high quality food items might engender "prehensile" appendages (I am looking at you ankylosaur tongues).



Anyways,

There is no terrestrial predatory tetrapod alive today that shares the suite of characteristics that T. rex has and which also has tightly sealing lizard lips. Asides from the vagaries of what can be gleaned from being one bracket closer on the subjective extant phylogenetic bracket in choosing the Komodo dragon as the best analog I would suggest that we look at the complete adaptive package of T. rex /tyrannosaurids and find the best and most comparable extant analog. Tyrannosaurus rex and other tyrannosaurids line up more closely with mammalian predators in terms of  adaptive features including; a dominant nasal olfactory apparatus; heterodont dentition with precise "nipping" incisiform like front teeth; forward facing eyes; high metabolism; and an extensive secondary palate. I suggest that we have been more than a little hoodwinked by a serrated toothed, poisonous, scaly faced, fork tongued, and lizard lipped trickster in the Komodo dragon that fails compared to mammalian carnivorans in terms of nearly every metric listed when comparing tyrannosaurid facial anatomy, especially in terms of extraoral tissue (i.e. "lips"). 

Let the saliva spray!!

HorridRexDarkerSepia by Duane Nash

credit Carli Davidson

As I alluded to earlier in the post although I concentrated on T. rex this inquiry into lips may have implications for many theropods to varying degrees. Certainly I would hedge my bets towards more of the jowly type of lips in olfactory dominant tyrannosaurids and dromaeosaurids. There is room for nuance in many of the other lineages of theropods though; with variation ranging from more of the lizard type arrangement in some theropods up to this more jowly visage with all the various factors I mentioned in this post coming in to play: how important is scent? tactile prey handling or precision biting important? threat display important?

I also did not mention feathers in this post as this issue is taken up very well in this youtube video:


Feathers can be on top of skin, scales can be on top of skin but feathers and scales can not exist on top of one another.

And I am under no illusion that this post will overnight cause a whole scale reevaluation and overhaul in how we depict theropods. I fully expect most to adhere to the lizard's lip paradigm as that is what classic phylogenetic bracketing dictates. But in the end I find the lizard lips adaptation adaptively inferior to the bulldog lip adaptation. Ironically I have old images that still show lizard style lipped theropods which I still plan on using too... funny thing is I really wanted to concentrate on theropods other than T. rex but this is where my questions took me!!

As I anticipated, reaction to my Hellhound rex bulldog lipped Tyrannosaurus rex argument was mixed. Some liked it, some were equivocal, and some were vehemently against it. You should know by now I have more than a little flair for the dramatic and don't think for a minute I have played my full hand when it comes to extreme "lippage" in theropods... That being said I took - for me at least - a very cautious, muted and tentative tone in that post. Not being naive and knowing full well that the backlash yet to come and the strong culturally entrenched reaction against extreme "lippage" in theropods going right to the heart of our cherished and idealized view of these animals... the struggle is real.

So in this post I am going to eschew that waffling, tentative tone and go right in for the kill shot. Yup names will be named. Things will get messy. Feelings might get hurt. Reputations might get questioned. Including my own but that's ok I am willing to play the villain.

But...

I did go through some real searching in how I wanted to approach this post. I mean the good and bad thing about blogging is you can see where and how traffic gets shuffled to your site which means that you get to read the things people say about you - and it does affect you deeply. In various form I have been called overly speculative, aggressive, a bit of a bully, not to be taken seriously, and sort of a mean and angry guy. And I get it why people say these things about me. I have always indulged in what I consider plausible speculative possibilities. I fully admit that I have a bit of chip on my shoulder that has a lot to do with not getting recognition and blogging not being recognized as a form of science communication on par with the "peer reviewed word" but I think that is changing. I have no problem calling out the "luminaries" of the field when they leave out data, make less than ideal suggestions, and use the weight of their name as a bully pulpit. At the same time I am fully confident that if you spent any amount of real time in the flesh with me you would come away with a perhaps very different or at least more nuanced impression of me than the above characterizations. I have also seen it written that I am too passionate and excited about my own ideas. "Too passionate and excited"... think about that for a second.... I've said it before and I'll say it again there is a little too much tone policing in paleo these days when passion and excitement are discouraged. If you have not noticed science is in a war and is failing to create the excitement, fun, enlightenment, fullfillment, and yes mysticism that other forms of belief are giving people for better or worse.

Never the less it is a hard thing to tell someone that a significant chunk of their life's work is obsolete and you have to be just a little bit of a bully to do so.

To quote the great "Nature Boy" Ric Flair: "To be the man you gotta beat the man!! Whoo!"




To really s - p - e - l - l it out for you I am make the allusion to "professional wrestling" to evince the level of venom, anger, and aggression in my heart - none at all really. It is all a bit of a bluff theatrical arrangement. Of course tone has a way of getting misconstrued in writing. And no, I am not on cocaine.

That being said I am really going out to pick a fight on this one and you better believe I am coming in swinging, guns blazing, and with the gusto!!

La Brea Tar Pits. Charles R. Knight public domain

There is a bit of a problem in sabertooth paleontology. An echo chamber has evolved where one man and one man only seems to dominate the narrative over this eco-morphological grouping of animals. And that man is Mauricio Anton whose books, papers, artwork, and blogging have cast a heavy influence on our view of these animals. Truth be told he deserves the recognition and there is good reason for this respect. His artwork is captivating and in a class of its own. His books are well written, engaging, and straddle the difficult line between being overly technical and approachable. However when the artistic and scientific leanings of only one man become the main voice heard or recognized that is never a good thing in any social or scientific activity. Biases can and do slip through. Unconscious memes passed on.

Charles R. Knight. Public Domain

In the case of this one aspect of sabertooth predators that I will be addressing the cultural transmission of this meme has gone on and on for some time now, Anton as the de-facto principal conveyor of sabretooth aspect and imagery merely inherited it from Knight and paleoartists/paleontologists of the past. It is not really his creation. However Anton "is the man" in sabertooth paleobiology and paleo-art. Heavy lies that throne and any reappraisal of sabretooth anatomy and imagery can not eschew mention of his influence. There really is no way to avoid going through him.

Enough beating around the bush, it's time for Mr. Sabertooth Tiger to get some self respect, stop walking around all exposed, have some decency AND COVER UP THOSE DAMN DAGGERS!!

Yup, sabertooth predators its time to grow up and cover yourself properly with nice big luscious lips sheathing your cherished daggers. You know, like is the case for EVERY EXTANT MAMMALIAN TERRESTRIAL CARNIVORAN. Is that phylogenetic bracketing enough for you? Truth be told phylogenetic bracketing should never be looked at as the ultimate truth, just a rough road-map. It is always better to take a pluralistic approach imbuing the EPB with a heavy dose of adaptationism - Stephen Jay Gould be damned. That is the approach I took with my last post on a heavily lipped T. rex and it is the method I will take here. One caveat of the adaptationism approach is that the feature you are looking at should be one that has a strong influence on survivorship and hence sexual success. So yeah, I think a feature intimately influencing, protecting, lubricating, and assisting in killing via those precious daggers counts in that regard in a very robust way.

"But what about elephants, walrus, and other tusked mammals? Their teeth are exposed all the time."

Pacific Walrus. Cape Pierce Public Domain

You know, I have to admit to throwing up a little in the back of my mouth whenever I hear this argument trumpeted out again and again. First of all it is moving further and further away from the extant phylogenetic bracket. We already have tons of living extant carnivorans to infer from, all of them cover their teeth completely or mostly. Even the clouded leopard the cat >most< often compared or likened to sabertoothed predators covers its teeth with a nice set of lips. Secondly, tusks don't even compare in form or function to saber toothed canines. Tusks are robust, coarse choppers for plowing into trees, roots, gouging into sediments, and >most importantly< fighting with and intimidating rivals. That they are always exposed has a lot to do sexo-social signalling. Sabertooth canines do none of these activities, are often serrated, and are intrinsic to survivorship. Tusks are always out and on display because a better strategy for always getting into costly and risky fights is to bluff your way to the top by always having your weaponry out, exposed, and in full view. Sabertooth daggers were not sexo-social displays and/or fighting tools, an argument Anton (among others) has summarily dismissed. Finally tusks keep growing in many animals that have them. Sabertooth predators had no such luxury. Comparing sabertooth daggers to tusks is like comparing a surgeons scalpel to a machete - a machete that keeps growing back. As you can tell I don't take this argument very seriously. In fact I would call it special pleading.

clouded leopard. credit Vearl Brown CC2.0

clouded leopard skull

We already have numerous and unequivocal osteological evidence of direct evolutionary pressure on sabertooth predators to sheath and protect their cutlery.

Rubidgea. credit Ghedoghedo CC3.0

Thylacosmilus atrox. credit Claire Houck AMNH. CC2.0

Machaeroides eothen. credit Ghedoghedo. CC

Pogonodon platycopis. Edward Drinker Cope public domain

Eusmilus. wiki commons

Hometherium crenatidens fabrini. Public Domain

Above you see examples of the bony correlate in all six of the respective sabertooth predator radiations; gorgonospid synapsids; thylacosmilidaen metatherians; machaeroidinean creodonts; nimravidaen carnivorans; barbourofelidaen carnivorans; and felidaen carnivorans.

It is in the form of the mandibular flange. In some examples it is quite profound, in others it is a little incipient. However it occurs in all radiations of sabertooth predators giving us a strong example of convergent evolution. But to expect evolutionary pressures to exert an influence on just the mandibular, inferior section of the tooth and not expect protection from above - where blows are most likely to come from? Evolution are you drunk? Should we really expect evolutionary pressures to exert an influence on protecting just the bottom aspect of the dagger and not the top? Really, you think so? When you blink does your eyelid only cover half of your eyeball? Does a turtle carapace only protect half of the turtle? Does your cranium only cover half of your brain? Sounds like a very half-assed protective strategy to me.

Instead I would argue a much more robust inference is that ALL sabertooth predators protected their cutlery from above and below. Some species show evidence of the inferior protection via the mandibular flange which itself was sheathed in a very rugged and durable layer of "skin" a lot like the darker area of the jowls you see in your own pet dog. The upper protection would come from a fleshy expansion of the upper lip region - just as you see in any felid or carnivoran today - except larger. As sabertooth predators evolved larger and longer daggers so to did the soft anatomy that protected and assisted them evolve in tandem. Pull up the upper lips to expose teeth and bite. Let lips go loose when teeth are not in use. That a Smilodon with big droopy facial lips seems shocking now is only an artifact of the cultural shock of multiple decades of toothed exposed iconography.

Such protection would not be 100% but I would hedge my inference in favor of protection rather than not. If a feature can evolve that can assist in the struggle for survival, then it should be there.

"How dare you compare sabertooth lips to the lips of artificially selected dogs and cats? Stop it."



Nope, not stopping. The reason I posit this distinctive bulldog looking Smilodon is that artificially bred mammalian carnivorans aptly demonstrate that there is a lot of plasticity in the facial region of these animals. That humans bred them this way for looks, for better scenting abilities, for whatever... I don't really care. All that these domestic breeds show me is that giving the evolutionary context and pressures (i.e. fleshy lips to protect large dentition) there is the genetic potential in mammals that such a look >could< evolve in a wild extinct sabertoothed animal. That the bulldog look comes about is, well, try drawing a sabertooth yourself and the only prerequisite is that the teeth are mostly or completely covered by lips and it is hard to avoid the bulldog look.

Extensive Lips & Fleshy Oral Tissues Allows Enhanced Proprioception of Sabertooth Head & Daggers in Relation to Prey. We Have Direct Osteological Evidence Of This Too.

As tool using, reduced canine having primates I think we often fail to appreciate the risks incumbent upon biting down into something that does not want to get bitten into. I mean, it is a pretty simple thought but revelatory at the same time. You are literally ramming your most vulnerable external body part into another organism latching onto and often holding onto them. Let me restate that again: your most vulnerable body part is in direct line of fire for whatever you are attempting to latch onto. Remember you have to do this again and again to make a living so to speak ecologically. All of these pitfalls would be especially true for sabertooth predators which seem to show a penchant for not only large, strong and retaliatory prey but direct and relatively prolonged contact (i.e. not a bite and flee predator but a tackle, subdue, and bite predator) in which their vulnerable daggers are put into jeopardy. If there is ANY advantage you can potentially and reasonably evolve that helps you to make a killing safer, quicker, and more efficiently then that evolution will likely occur and the inference is a robust one.

Large fleshy lips and oral tissue not only provide a better means of protection from struggling prey (although not 100%) but they also provide a larger and more extensive tactile surface area to position the teeth for efficient and safe biting.

Let me just quote Anton directly here from his book Sabretooth (pp 178-79 Sabretooths as Living Predators):

"One consistent feature of most sabertoothed carnivores is the relatively large size of the infraorbital foramen... (discussion of potential muscular insertion, rodents, Barbourfelis)... there are other structures that pass through infraorbital in all mammals - specifically, the infraorbital nerve, veins, and arteries. The infraorbital nerve is a branch of the maxillary nerve, and it provides sensory nerve endings to the whiskers. Once the nerve crosses the canal, it begins to branch; and when it reaches the roots of the whiskers, it forms a true "nerve pad," creating a characteristic swelling on the sides of the muzzles of many mammals. Thus, one tempting explanation for the large diameter of the opening in sabertooths would be the presence of very well developed, especially sensitive whiskers with rich innervation."

While Anton later tempers his stance mentioning issues of direct proportionality he does mention that " the relationship between the development of the foramina and the function of the infraorbital nerve is widely accepted among zoologists."

I would go further and posit that the reason the infraorbital foramen is relatively larger in sabertooths than other predators is that not only was the "nerve pad" more sensitive - it was also absolutely larger than the nerve pad in extant felids. Why such a large and sensitive nerve pad would be needed in these predators is fairly obvious in terms of making precise and safe incisions into struggling and retaliatory prey that could easily snap off or damage your cutlery.

Anton pp 179:

"... the killing bite of sabertooths must have been quite precise in order to avoid accidents involving lateral torsion or hitting a bone in the prey, which could cause the sabretooth to break a canine. Since the target area of the bite would be outside the predator's visual field, the tactile information provided by the whiskers would be especially useful for the precise control of the biting motions. Modern cats are able to move their whiskers thanks to well developed piloerector muscles, and during the killing bite the whiskers are usually directed forward, enveloping the bitten area in a sensitive net of hairs (Leyhausen, 1979). Given the additional risks imposed by fragile sabers, improved perception would be a useful trait for the sabretooths."

I like and agree with everything Anton says here. I just differ from him in inferring an absolutely larger "nervepad" that would ultimately be more adaptive than the smaller nerve pad he prefers that only partially cover the daggers as depicted in his and all others' paleoart. I can already picture some people saying "well what if the whiskers were just longer?" nah, always better to have the tactile ability and protection. That is the more adaptive and reasonable inference not whiskers creeping down like daddy-long legs.

credit Nick Farnhill. CC2.0

As you can see in the above pic of a cheetah throat clamping Thompson's gazelle - in which the canines clamp shut the windpipe and kill by suffocation - the sensitive nerve pad is deeply enmeshed in this activity. Indeed as the bite occurs in a blind spot for the cat it is the nerve pad, especially via the whiskers, that most accurately dictates to the predator where and how the clamp should be applied. Let's think about this for a second. Many modern large felids clamp the windpipe shut with their relatively stout and blunt canines. That is a pretty refined and delicate approach and the utility of having the sensitive muzzle and whiskers enmeshed in close proximity to the bite area is self evident. However when we contrast this method with how sabertoothed predators - especially the "dirk toothed" cats likely killed - they were looking to inflict massive trauma to the general fleshy region of the neck (but also possibly abdomen). Whether the killing stroke severed arteries or the windpipe or both not really important as the end result is the same - death. So if you think about it the killing method of such sabertooth predators is  less precise than many modern felids -  as long as they get their bite in the general non-bony area of the neck (or abdomen) they good. SO WHY WOULD THE INFRAORBITAL FORAMEN BE RELATIVELY LARGER IN SABERTOOTHS? The logical conclusion is that the "nerve pad" was not relatively more sensitive per surface area than modern felids, it was in fact absolutely larger than modern felids and likely equally innervated and fed with adequate blood supply. This soft tissue adaptation would cover up those precious daggers and provide the tactile support to place the daggers in the right spot to make a killing stroke without risking torsional twisting of prey or bone chipping.

Additionally when we consider how this biting action would look and function in a sabertooth with the traditionally depicted modest sized nerve pad a real dilemma occurs. Due to the large size of the daggers - especially extreme in genera like Smilodon - the sensitive nerve pad would be scrunched up and pushed away from the bite area and not very useful for "feeling out" the best place to position a bite when the mouth was open. Indeed it would be the large teeth "feeling things out" - exactly the problem sabertoothed predators want to avoid!!

Ki Andersson, David Norman, Lars Werdelin - http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0024971

You can easily see what I am talking about using this kinematic illustration above. The sensitive nerve pad would be nowhere near the bite area in traditionally depicted sabertoothed predators. But if we infer a large upper lip and nerve pad that completely or nearly completely sheathed the upper teeth even when the mouth is opened then you have a much more efficient and safer ability to "feel out" where and when to engage the teeth with prey. In this manner the teeth are protected and sheathed until the final split second before impact and the upper lip is pulled back to reveal the daggers. The tough and elastic lip need not even be pulled back that far because as the daggers are plunged into prey the body of the prey itself would simply push back against the lip sliding them back further. Large upper lips provide the most safe, efficient, and osteologically corroborated method of biting possible.

"If only we had evidence for sabertooth appearance via cave-art or other ancient depictions" ... well maybe we do.

Yup it is time we revisit the potential Rosseta Stone of sabertooth life appearance: the paleolithic statuette from Isturitz.


Now I want to make it clear - this is an artistic representation by Mauricio Anton based upon the rendering of Czech paleontologist Vratislav Mazak who himself saw representations of the original statuette in 1970. Long story short nobody actually has the statuette as it has been lost since at least the early part of the 20th century. As the statuette has been lost and been redrawn at least two times, maybe even three times as Mazak himself is said to have only seen "representations" of it, the logical conclusion is that there is a lot of ambiguity in this piece. Furthermore as the original piece can not be directly observed i.e. it can not be "tested" by others it should be in fact stricken from scientific discourse. I mean, am I wrong? Is that not the argument put forth why "private fossil specimens" can not be part of the recognized science as they can not be first hand analyzed, observed, and tested by all parties... am I missing something here? Never the less the Isturitz statuette representation has made it through peer review and is part of the "recognized" scientific literature despite the inability to test it (peer review fail #1).

In his paper reconstructing the musculature and facial anatomy of Homotherium latidens (Anton, et al. 2009) steer away from Mazak's interpretation of the Isturitz statuette representing a late surviving Pleistocene Homotherium and instead side with the original interpretation of cave lion. In Facing Homotherium Brian Switek summarizes their argument succinctly:


It should be noted that this analysis dovetails into the facial reconstruction that Anton et al perform on Homotherium in the same paper.


 Compared to:



And a cave lion representation:

Replica Chauvet Cave Lions, France

While Anton et al. do provide some compelling arguments concerning body proportion and the lack of a sloped back in the model as Homotherium would have in life (sort of like a spotted hyena) these gross anatomical inferences can be explained by the lack of forefeet in the statuette which may influence how the posture is meant to be; the possibility the figure represents a dead or lying felid; and simple errors on the part of the artist.

On the chin argument I find it less than compelling that the strong chin and large lower jaw represents the tuft of hair on a lion. It just looks too prominent and large in my eyes and is more consistent with the mandibular flange of Homotherium. There is no abrupt transition from the chin to the neck line as should be expected if the chin was simply a tuft of hair. Furthermore the manner in which Anton et al reconstruct the jaw in Homotherium is inconsistent with how we or most animals actually hold the jaw in neutral pose. They pose it in "extreme" jaw closure as if the animal would be walking around clenching its teeth shut - similar to the argument put forth on extreme jaw closure in tyrannosaurids and other theropods debunked in my last post. I suspect most animals (including you as you read this unless you are like really mad right now ;')  have their jaws just slightly agape in the neutral pose. This would dissuade the need for the teeth to fit into pockets of flesh in the lower jaw as suggested by Mazak and argued against by Anton et al. (sort of like male baboons) but instead the whole upper canine would simply be sheathed by the upper lip/nerve pad. When the jaw was fully closed it would simply lie against the thick tough, elastic, and lubricated skin of the lower jaw. Just like a clouded leopard which, by the way looks to have canines at least as big or bigger as Homotherium relative to its head size.

There is a bit of a tendency in paleo for people to see beautifully rendered muscular and skeletal reconstructions  of extinct animals and take them a little too literally. When in reality there is a lot of guesswork and biases at play in even the most "rigorously" reconstructed extinct animal no matter how aesthetically appealing. In the paper Anton et al. provide a list of references for how they reconstruct the soft tissue for Homotherium latidens:

"For soft tissue reconstruction we followed the methodology outlined in our previous works (Anton, 2003; Anton & Galobart, 1999; Anton & Sanchez, 2004; Anton et al., 1998; Turner & Anton, 1998)." 

Notice any pattern there? If a guy with the last name of Anton is the lead author of the paper and the source methodology for reconstructing soft tissue is also culled from a guy with the same last name it is not unreasonable to suspect a certain unanalyzed bias to seep through? Could there be a bit of an echo chamber here?

Anton et al., also cite the extant phylogenetic bracket as defined by Witmer as a means to infer soft tissue. But what this method lacks is putting soft tissue through the lens of adaptationism.

Anton et al. also assert that if the canines are long enough they should be seen passing past the upper lip. As evidence for this assertion they cite one example of a canine peeking past the upper lip in a dead lioness they dissected.




Now, you need not be a statistician to realize that when N=1 that is not a very large pool of a sample size to draw meaningful data from. Additionally, you need not be a mortician to realize that when stuff dies things change. Muscles grow tighter drawing back soft tissues. Mouths clench shut potentially. Anton et al. did not account for this or even mention these obvious pitfalls on drawing anatomical conclusions from a cadaver of one sample size (peer review fail #2 ). Better to look at live animals. And when you look at live carnivorans - especially felids - the upper canines are completely or mostly sheathed by the upper lip and the mouth is not clenched shut but slightly agape. Go ahead and peruse google images of large felids and see where the bias lies in terms of canines exposed or not. I double dog dare you.

Other facial features that the Chauvet lions display that are not concordant with the Isturitz statue are that the ears of the cave lion are rounded while the statuette's ears are very distinctively pointed. The spotted pelage and what appears to be a countershaded line along the torso in the statuette also do not match well with the striped pelage that has been suggested for cave lions from ancient cave art. This is a notable omission and Anton et al. deserve to be called out for not mentioning these anatomical incongruity. ( Peer review fail #3 & #4)

One of the more interesting ideas put forth is that the figurine represents a cub due to the big eyes. However I am not sure if those eyes are just stylized and if such a bold chin would be consistent with a cub lion. This idea might explain the spotted pelage as cub lions have spots and then lose them; on the other hand the cubs of striped tigers are not born spotted they are always striped.

And finally the tail. Homotherium has a bobtail while cave lions do not. Is the tail broken off in the statuette? I don't know, we can't go back and analyze which is why it probably should not have got into the scientific literature in the first place!!

Finally it is interesting that - if cave lions had manes like modern lions - a female lion would be chosen for the statuette, and not a male. I mean if you look at iconographic imagery of lions made by humans the male lion predominates in representation. It is larger, has a striking mane, is more powerful and the symbology to "warlike" civilizations is obvious; but perhaps the female lion was actually the preferred symbolic analogy used by paleolithic cultures and they in fact had a different set of cultural values than modern humans...

As you can see we are clearly in the subjective zone on this one. Switek says it takes a lot of special pleading to infer that the statuette represents Homotherium but I say it takes just as much, if not more, special pleading to infer it as a cave lion.

Look the statuette can be argued about until the cows come home - which I will abstain from doing so in the comments section so don't even try and tempt me... But it is a compelling and interesting story.

On a bigger level  this whole discourse is a great lesson in how bias can go unseen and get propagated seemingly without question.

If you go back and read the selection I culled from the Switek article he states his bias right up front:
"... and there is no reason to believe that the canines would have been covered by lips in life."

Let me just refresh you on the talking points on why large lips covering teeth should not only be the belief but the null hypothesis that should be disproven in extinct mammalian carnivorans; all modern terrestrial mammalian carnivornans sheath most or all of their teeth in lips and flesh (EPB); an extensive and proportionate "nerve pad" inferred from large infraorbital foramen located proximate to canine entry assists in vulnerable and precise tooth entry; protection of teeth, especially canines, from breakage and grit; osteological evidence of mandibular flange in sabertoothed predators infers complimentary protection from above.

It may appear that I am picking on Brian here but really he is just a fill-in for many of our biases favoring tooth exposed extinct predators, including until recently myself. Darren Naish seemed to have been favorable to the Isturitz statuette representing a late surviving Homotheriumwhen he discussed it way back in 2006. However after Anton argued otherwise Darren seems to have changed his mind in 2010. However if you look through the comments section in that post you will see that longtime Tet Zoo commentator Jerzy makes many of the same arguments (except I don't think the canine teeth need fit into pockets like in male baboons as suggested by Mazak as well) I am making and calls out several omissions from the Anton paper:



Evidence of Morphological Features Evolving in Tandem With Increasing Canine Length In Sabretooth Predators

As cultural creations as much or even more so than scientific ones it is always useful to brace yourself for the shock and cognitive dissonance of a cherished and loved extinct animal taking on a radical, bizarre new look. We see this startling and immediate transformation but I don't think that we always appreciate that an organism is the product of evolutionary pressures and compromises occurring to it and molding it over millions of years. From our perspective large lips smothering a Smilodon's face appear to evolve over night but in reality the large lips and large teeth would be evolving in tandem as each feature influenced and reinforced the other in a feedback loop. It is only the shock and awe of seeing this change so sudden and profound that we rebel against it.

My contention that increasing lips evolved in tandem with increasing canine size is bolstered by a study showing the exact same correlation of increasing forequarter and forearm strength in sabertoothed predators occurring in concert with increasing canine length. Powerful Arms Saved Sabretoothed Killers' Fearsome Fangs, Study Shows


Julie Meachen-Samuels:

"I found that they had very thick humerus cortical bone, much thicker than any non sabertoothed cat living or extinct... I hypothesized that this extreme cortical thickness was correlated with the extremely long sabers. The robust limbs allowed Smilodon to restrain its prey so that it would be able to make a killing bite without damage to its saber teeth... These traits evolved as not only a suite of characters but as a viable distinctive prey killing strategy several times independently. This combination probably evolved several times because the predators that could best protect and preserve their teeth during prey killing survived longer and could have more offspring, thereby making this combination of long teeth and strong forelimbs a winning combination."

So should I connect the dots? Canines start growing a bit longer, lips evolve in tandem to sheath, protect, lubricate, and provide optimal tactile sensory usage. Forelimbs and forequarters get more robust to further the safety and efficiency of the kill. Canines grow a little longer still as do the lips and forequarters. The animals that can best protect their teeth and live longer reproduce the most even if it is just by incremental percentages. Repeat, repeat, repeat until you get something that looks like this:

Duane Nash. EatYourKittenSmilodon

The thing is you can still haz ur scary Smilodon even with the lips covering the fangs. It is often times what you don't see that scares you the most. If anything the big, jangly jowels add a surreal and disturbing touch. And it is all too easy to imagine that upper lip being pulled back to reveal that staggering dental load just glistening with lubricating juices and ill intent.

So just one more time to hammer down the talking points:

Facial tissue completely or mostly sheathing the upper canines as is corroborated by ALL extant terrestrial mammalian carnivorans and is the best null hypothesis; exposed and constantly growing tusked mammals use their non-serrated tusks for coarse hacking, chopping, digging, combat and display and are an inferior analog to sabertooth canines and need not be considered as they fail in comparison along nearly every metric; the clouded leopard which has long canines comparable to many sabertoothed predators covers its canines completely; all five radiations of sabertooth predators display osteological evidence of protective sheathing on the lingual inferior aspect of the canine via a mandibular flange - a logical evolutionary inference is that protection for the superior labial aspect of the canine was also selected for in the presence of a large fleshy upper lip; the presence of this large fleshy upper lip is corroborated osteologically by the relatively large infraorbital foramen found in all sabertooth predators; this large infraorbital foramen supplies the blood and nerve supply to an extremely large and sensitive "nerve pad"; the extremely innervated nerve pad provides tactile support to make precise and crucial placement of canine entry for bite; such tactile support would be diminished in sabertooths depicted with modest sized upper lip region as this area would be scrunched away from the bite area when the mouth is opened and it would be the vulnerable canines that would "feel out" where to bite; large lips and supporting nerve pad evolved in lock step with increasingly large canines and forequarter strength for maximum safety and efficiency in these highly precise yet vulnerable predators.



And I did not even mention the benefits of; having your serrations free of grit & abrasives; accruing scent particles on a larger "environmental swab"; lubrication for cleaner cutting; and preventing excess moisture loss.



Or you can keep your feebly lipped, tooth exposed, non-tactile, maladaptive, vulnerable, culturally enshrined, and just plain weird looking sabertooth predator. But I say you are holding onto a dream... Yup puny lipped advocates it is you and not I that need be on the defensive on this one. Your creature is the myth - not mine. Script. Flipped.

"It is the responsibility of the scientific paleo-illustrator to make sure that his images rigorously transmit the knowledge that the paleontologists have gathered from specific extinct species."

-Mauricio Anton

*Clarification. I can already see some people misconstruing what I am suggesting with the notion that the upper canines fit into "pockets" formed by the lower lip and the mandible as suggested by Mazik. I don't think this was the case as at all. The upper canines simply rested against a more extensive lower lip region that was very durable and tough tissue - again not unlike the tough, elastic usually dark lips of domestic breeds of dogs that have had this feature artificially enhanced. Also don't confuse what I am suggesting with the debunked notion of G.J. Miller who suggested a quasi- "bulldog" look but for other reasons than what I am suggesting. Miller thought that the lip was retracted backwards to allow proper carnassial use due to the canine length. However this premise is faulty because such a lip would cut right into the masseter muscle and it is not needed anyways as modern felids are able to use their carnassial teeth without opening their mouth all the way.

References

Andersson K, Norman D, Werdelin L (2011) Sabretoothed Carnivores and the Killing of Large Prey. PLoS ONE 6(10): e24971. doi:10.1371/journal.pone.0024971

Anton, M. 2013. Sabretooth. Indiana University Press

Anton, M., Salesa, M.J., Turner, A., Galobart, A., Pastor, J.F. 2009. Soft tissue reconstruction of Homotherium latidens (Mammalia, Carnivora, Felidae). Implications for the possibility in paleo-art. GEOBIOS 42 (2009) 541-551

Cohen, Jenny 2012. Powerful Arms Saved Saber - Toothed Killer's Fearsome Fangs, Study Shows. January 4, 2012.

Meachen-Samuels, J.A. 2012. Morphological convergence of the prey killing arsenal of sabertooth predators. Paleobiology 38(1): 1-14

Naish, Darren. 2006. The late survival of Homotherium confirmed, and the Piltdown cats. Tetrapod Zoology. Thursday, March 9 2006

Naish. 2010. Tetrapod Zoology Book One is Here At Last. Tetrapod Zoology. October 7, 2010

Switek, Brian. 2010 Facing Homotherium. WIRED. November 18, 2010


Cheers!!

I knew in my last post that some might take exception to my tone a bit... ahem... maybe the 'rastling analogy went over their heads. I went with my gut and my gut said take the fight to 'em which is what I did knowing full well that the blowback would be real and palpable. However the blows I delivered came in the form of valid, scientific arguments.  The majority of blows I received were anything but.  Again some might take exception to my approach calling it "antagonistic " or "childlike" but these critics did not get attacked like I did. No one enjoys getting called "inane", "ludicrous", or a "jealous idiot" (Ok I might be jealous some times and an idiot at other times but never the two at once). But this is all the majority of the arguments really amount to; name calling; dismissive; and clinging to custom. While there were some intelligent questions and criticisms I did not find any of them damning to such a degree that they warrant scrapping the hypothesis. Indeed the multiple lines of evidence I offered in that post will be further augmented in this post to such a degree that any attempt to invalidate this hypothesis need to disassemble each individual argument one by one not merely poke holes in individual arguments to cast shade. Because as much as I pleaded and prodded for scientific reasons why a small lipped sabertooth predator is the better and more supported option than what I suggested I received nada. Nothing. Nunca. There is literally nothing that puny lipped sabertooths give advantage to over big lipped ones. Indeed big lipped sabertoothed predators should have always been the null hypothesis but cultural inertia, dogma, and "awesombro" exposed toothiness got in the way.

Smilodon populator. used w/permission credit deviantartist Dontknowwhattodraw94 (Robin Liesens)

Here is a more classically felid look that could work too.

All the while I knew that if I shook the tree hard enough something might just fall out... which it did and it splattered everywhere.

Time to crack this thing wide open...



And crack is the word of choice here because as traditionally depicted cracking is what sabertooth canines would be doing a lot of. Not just because of being exposed to blows from prey/competitors. Not just because of grit working away at the denticles. But because of chemistry.


Special kudos to Brad McFeeters for turning me onto the abstract of an as yet to be published work on the relationship between enamel health, saliva, and closed oral lips. Something any good dentist could tell you. Indeed it was a man who said he teaches students taking the dental admission test that presaged this very fact to me in a comment from my last post:


Please excuse the "appeal to authority" but it is none other than the American Dental Association that refers to saliva as "the bloodstream of the mouth" :



Intuitively this makes complete sense. Ever fall asleep with a stuffy nose and then wake up with a mouth that feels like a crypt? The bad breath and general oral malaise of just spending one night with your mouth exposed and dried out is but a preview of the dental horrors that would befall a sabertooth predator spending a lifetime with its physiologically expensive canines unsheathed.

Here is an excellent, easy to follow, and well referenced summary of the benefits of saliva by the European Food Information Council:  Saliva - more than just water in your mouth

Of special relevance is the chemistry of saliva which is crucial in maintaining the mineral balance of tooth enamel and dentine and preventing the loss of calcium and phosphorous. I am not going to pretend to be a chemist or that I can explain it any better than they do so let me just outsource their summary below:


Essentially not having saliva - which is buffered with loads of calcium and phosphorous - would open up the crystal structure of hydroxyapatite (the building block of dentine and enamel) to chemical attack.   The attacking molecule that would strip calcium and phosphorous out of the crystal structure is... water "in water the crystal would steadily lose ions form the surface and shrink". Best keep your cutlery sheathed and lubricated with saliva otherwise you are looking at some brittle canines because water is pretty much everywhere!!

Time To Stomp the "Tusk" Argument to Smithereens


Clearly I did not state my case strongly enough in the previous post that the last thing you want to compare sabertooth canines to is tusks which differ in just about every fundamental metric from sabertooth canines. Never the less you still have people chiming in "but what about fanged deer"? Please don't insult these proud and magnificent predators by comparing them to..... deer ( I jest, just a little). To be fair musk deer have continual growth of their canines and as I will explain shortly tusked deer will most likely share histological features of other tusked animals. Let me reiterate; tusks are sexo-social symbols and hence need to be displayed while sabertooth canines are not; tusks are used for not only combat but coarse gouging of sediment, bark, roots, and other gritty abrasives - sabertooth canines do none of these activities, in fact to the contrary, the fine serrations on many sabertooth canines would be damaged through excess grit; tusks grow constantly, sabertooth canines do not. These are all patently good arguments that are also essentially adaptationist in their approach. However paleontology and evolutionary theory have fallen out of love with adaptationism to some degree dismissing such arguments as "just so stories". I blame Stephen Jay Gould for this pervasive sentiment. I don't mean to kick a man when is down (literally six feet under in this case) but Gould was a little less than precise in giving us good examples of evolutionary spandrels after all. But I digress.

This just means I got to look a little bit harder and deeper than "just so stories" to persuade people that tusks are the last thing that you want to compare to sabertooth canines. Luckily enough for us there is quite a bit of information out there on tusks because ivory - the cultural trade and carvings of large animal teeth - has been a pretty important thing in human economics that people have looked at. When we investigate the histology of  tusks (i.e. large exposed teeth) there are some interesting surprises...

credit USFW services

Notice that in the schematic above there is just a bit of enamel at the tip but the bulk of the external layer is actually cementum, followed by dentine. Now in the hierarchy of hardness scale enamel is hardest, then dentine, and finally cementum. However given that enamel occurs only at the tip where it is actually worn away during the life of the tooth it is a bit of a paradox. Why would tusks - which are subject to all sorts of rough and tumble activity - only have such a paltry layer of the hardest structure which is enamel? Not only that - it is counterintuitively cementum that covers the bulk of the exterior of tusks which is the softest of the three materials? It's a bit of a paradox that tusks disinvest in enamel but invest heavily in the softer tissues of dentine and cementum (also btw which is why ivory can be carved). The reasons I would suggest are manifold:

1) Enamel once it is formed can not keep growing, only maintained. Dentine on the other hand can be grown continuously via odontoblastic cells in the pulp cavity - which is why tusks keep growing. Cementum too can repair itself and grow continuously via cementoblasts.

2) Enamel is the hardest structure of the three but also the most expensive physiologically to grow, form, and maintain. Minerals are very precious things after all and investing so much mineral wealth in a structure that will be winnowed away is maladaptive.

3) Because the enamel in tusks is not constantly bathed in a buffering solution of saliva that maintains calcium and phosphorous balance of the crystal structure it is prone to not only physical attack but chemical. The investment of enamel in the tip of the tusk is a throw away investment. Over time it will be lost. From USFW on elephants/mammoth tusks: "Enamel is only present in the tusk tip in young animals. It is soon worn off and not replaced."

4) I will suggest that cementum and to a lesser extent dentine - having less of a solid crystalline structure than enamel and a higher percentage of other protein tissue that form it (e.g. collagen) - are less subject to chemical attack than enamel in the exposed state and offer an ideal compromise: just enough hardness to get the job done without the excess chemical attack that enamel suffers. Again, both dentine and cementum can grow constantly while enamel can not.

If this is a robust and true pattern we should see it again and again in animals that leave their teeth (i.e. tusks) exposed to the air. Through convergence this prediction should be met and these animals will disinvest in enamel on the exterior layer of the tooth and have relatively higher investment of the less mineralized and softer dentine and cementum.

And gee willikers look what we have here:

Walrus (Odobenus rosmarus)

From the USFWS: "The tip of a walrus tusk has an enamel coating which is worn away during the animal's youth."

cross section walrus tusk. C=cementum, PR=primary dentine, SD=secondary dentine

Also of note cementum is softer than dentine. This follows the somewhat counterintuitive pattern in having the least mineralized (softest) part of the tooth exposed to the environment as to not become demineralized. The cementum literally shielding the dentine from exposure.

Sperm and Killer Whales (Physeter catodon & Orcinus orca)

From the USFWS: "Both species display conically shaped teeth with a small amount of enamel at the tip. The rest of the tooth is covered by cementum."

killer whale

Which of course reminds me of the population of offshore killer whales that specialize in feeding on deep water sharks. This population pay a heavy toll in the form of declining dental health with old adults in such populations showing severe tooth wear reduced to gumming shark liver and the young doing most of the tearing up. Not too surprising that captive killer whales have horrible dental issues as well.

Narwhal (Monodon monoceros)

From USFWS: The narwhal horn (actually a modified upper incisor): "Enamel may be present at the tip of the tusk."

Narwhal

Wart hog (Phacochoerus aethiopicus)

From the USFWS: "a longitudinal enamel band with approximately one-half to two-thirds coverage mark the tusk's surface in the raw unpolished state."

Wart hog

Hippopotamus (Hippopotamus amphibius)

From the USFWS: "A broad longitudinal band of enamel covers approximately two-thirds of the surface area of the tooth... The surface which is not coated with enamel displays a very thin layer of cementum... Hippo incisor crowns are covered with enamel."

Hippopotamus

Wait a second here, the hippo seems to be breaking the pattern of tusked animals that have minimal enamel coating on the exterior of the tooth. What is going on here? All is not as it seems with this tusked animal. The hippo is a tusked animal that keeps its tusks and dentition covered with big lips that don't quit. Therefore it gains the protective benefits of saliva and can afford to have enamel rich dentition. By the way why does no one consider the massive lips of hippos preposterous or ridiculous but big lips on a smilodon? that is just ridiculous.

credti Quartl CC3.0 Huge Lips to Cover Huge Tips

The Croc Question

"Ok then, what about crocs? They leave their teeth exposed to the elements - including water - which can itself strip away calcium and phosphorous?"

All is not as it seems as well with our smiling crocodilian friends. Their sinister smile betrays a sneaky way around the problem of exposed teeth. First of all - analogous to ever growing tusks of mammals  - crocodilian teeth have the ability to get replaced. Second of all crocodilian teeth show a histology more congruent with tusked mammals than the enamel rich dentition of mammalian carnivorans or predatory theropods. Their teeth actually act more like miniature tusks in that they too share the pattern of a thrifty use of enamel on the exterior.

A recent study of this very issue (Enax, 2013) provides some telling information:


Some things attract my attention here.

"Virtual sections through the tooth and scanning electron micrographs showed that the enamel layer is comparably thin."

To beat that drum again that is exactly the pattern in tusked animals with exposed teeth and opposite the pattern in animals with closed lips and sealed mouths that allow teeth to bathe in saliva and remain enamel enriched.

"The crystallites in the enamel are oriented perpendicularly to the tooth surface."

Very interesting here in that the crystal structure - being perpendicular to the tooth surface - is oriented in a manner that minimizes exposure to the outside environment. Could a very logical (and adaptationist) hypothesis be that this orientation is not haphazard but in fact that it has selective benefit in minimizing surface area exposure to chemical attack from the environment?

From the discussion section and conclusion:




The authors explain the thin layer of enamel in crocodiles which contrasts to the thick layer of enamel in mammals due to "the enamel of crocodile teeth is very thin.. because crocodiles do not use their teeth for cutting and chewing."I don't really understand why people say crocodile teeth do not cut, I mean tell that to anyone or anything that actually who has got bit by a croc. Those teeth do cut. Point taken they are >mainly< graspers but they can inflict some pretty nasty damage as well.

Never the less it is readily apparent that the authors failed to compare croc teeth to exposed mammalian teeth (i.e. tusks) which they do share a convergence of composition, microstructure, and hardness. By the way also interesting that croc teeth compare in hardness with human teeth given the high disparity in bite strength. Probably helps in preventing brittle deformation in croc teeth but still strange to think about.

I would venture to say that in the worn teeth of old crocs all of the enamel has been worn off through either mechanical or chemical wear and you are in fact looking at the dentine after the thin enamel tip has been worn away.

any enamel left in those tooth crowns? I doubt it. American crocodile. credit Daderot public domain

 Shark teeth... well I don't even want to confuse the situation further.

The main point is that croc teeth and mammalian exposed teeth (i.e. tusks) show congruence in composition and structure that suggests a possible selective advantage in being thrifty with the amount of enamel coating the tooth. Tusk bearing animals that maintain an oral seal via lips such as hippo can coat their teeth with relatively more enamel due to the salivary benefits to enamel health.

So the million dollar question is: if sabertooth predators indeed left their canines exposed to the environment then they should show histological tooth characteristics similar to crocodilians and exposed tooth bearing (i.e. tusked) mammals such as minimal enamel coating of the tip and potentially a layer of cementum covering the coat of most of the tooth. If they were just good ol' mammals that kept their lips shut and their teeth sheathed and bathed in saliva then we should see bountiful amounts of enamel especially on the exterior of the tooth.

So which is it?

Unfortunately I can not find adequate and thorough histological work on the microstructure of all sabertooth predators. But I can find such work on the creme de la creme, el utlimo hombre of sabertooth predators Smilodon fatalis. If this predator keeps the pattern of thick enamel forming the exterior of the working tooth and not just the tip it squarely lines up with animals that cover their enamel rich teeth in big luscious lips and bathes them in a protective broth of saliva. And if this penultimate of sabertooth predators can cover its extreme canines with lips there is all the reason in the world to expect all the other sabertooth predators to fall in line.









From the paper Cementum on Smilodon sabers (Riviere & Wheeler, 2005) these depictions clearly label the cementoenamel juction. Everything on the exterior of the tooth towards the tip from this junction is enamel. Smilodon is not like a tusked mammal or crocodile but congruent with every other enamel rich mammal that sheathes its teeth in lips and saliva.

Interestingly the Riviere & Wheeler paper came to the conclusion that gingiva - in other words gum tissue - covered the root of the tooth all the way to the cementoenamel junction.

From (Riviere & Wheeler, 2005):


This interior soft tissue protection would inhibit infection, alveolar bone resorption, periodontal disease, additional tactile capability, and tooth stability. In short very consistent with the soft tissue benefits of large lips and a sealed oral cavity for tactile ability, protection, lubrication, and enamel health. It all meshes together to create a very gummy, lippy, and infinitely more adaptive vision of these predators than is classically portrayed.

used w/permission credit LWALTERS. deviantart page LWPaleoArt

Here is a more classically felid look that could work too.

This is for the haters - if your mind changes as the facts change this need not apply to you, move along and let it not apply to you - but if you attacked me with name calling or just dismissed my arguments as "ludicrous" then yeah, this is aimed directly at you. Can you feel that?



Call me childish, but hey, talk to me after you take a chance on something and take the shots I do. Gonna rub it in their face just a little bit.

And finally back to the yet-as-unpublished work by Robert R. Reisz that Brad McFeeters brought to my attention after the last post was published. Presented at the 2016 Canadian Society of Vertebrate Paleontology. Unpublished stuff is always "iffy" but hey if CNN is gonna cover it and the press is all over it then fair game for me I say. So far the press has put out the stock line you see in all theropod related news and somehow T. rex has to be the star of the show... all the while (predictably) ignoring the more obvious implications for sabertooth predators that this study also hints at.




I am very bolstered by the observations by Reisz and Larson on the histology of tusked mammals differing from theropods which converge with my argument regarding tusked mammals falling down as an analog to sabertoothed predators. However I would certainly encourage Reisz and Larson to look more closely at their statement "we propose that this requirement of hydration is not possible to maintain if the tooth is exposed permanently". As I discussed earlier saliva's benefit has much to do with maintaining chemical equilibrium of enamel while water that is not buffered with calcium and phosphorous can strip it away. Water has some pretty unique chemical properties (dipole moment, net negative charge) that can overtime strip enamel of positively charged calcium and phosphorous. Not saying that hydration does not play a role in all of this - it likely does - but chemical equilibria is another important aspect of enamel health. Again, remember hippos were the only "tusked" animals that have a lots of enamel on the exterior of the tusk but only because they keep them bathed in saliva.

To drive the point home one last time:

Facial tissue completely or mostly sheathing the upper canines as is corroborated by ALL extant terrestrial mammalian carnivorans and is the best null hypothesis; exposed and constantly growing tusked mammals use their non-serrated tusks for coarse hacking, chopping, digging, combat and display and are an inferior analog to sabertooth canines and need not be considered as they fail in comparison along nearly every metric; exposed toothed mammals (e.g. tusked) and exposed toothed crocodilians have differing tooth histology from sabertoothed predators*; unlike smilodon these animals have minimal enamel laid down at the tip of the tooth often worn away during the animal's lifetime; exposed toothed animals have an exterior tooth largely covered in cementum or dentine, both of which can grow constantly unlike enamel; saliva plays a crucial role in the dynamic chemical health of enamel; saliva provides a buffering role in hydroxyapatite crystal as saliva is enriched with calcium and phosphorous preventing demineralization of enamel; this salivary coating is only maintained in closed mouth (e.g. lipped) animals; the clouded leopard which has long canines comparable to many sabertoothed predators covers its canines completely; all five radiations of sabertooth predators display osteological evidence of protective sheathing on the lingual inferior aspect of the canine via a mandibular flange - a logical evolutionary inference is that protection for the superior labial aspect of the canine was also selected for in the presence of a large fleshy upper lip; the presence of this large fleshy upper lip is corroborated osteologically by the relatively large infraorbital foramen found in all sabertooth predators; this large infraorbital foramen supplies the blood and nerve supply to an extremely large and sensitive "nerve pad"; the extremely innervated nerve pad provides tactile support to make precise and crucial placement of canine entry for bite as well as early warning for violent torsional twisting of prey that could damage/snap canines; such tactile support would be diminished or non-existent in sabertooths depicted with modest sized upper lip region as this area would be scrunched away from the bite area when the mouth is opened and it would be the vulnerable canines that would "feel out" where to bite; extensive gingiva possibly reaching up to the cementoenamel juction protected, sheathed, and provided tactile support to the canines; large lips, gingiva, and supporting nerve pad evolved in lock step with increasingly large canines and forequarter strength for maximum safety and efficiency in these highly precise yet vulnerable predators.

Your puny lipped sabertooth kitty is not only smashed...  it is curb stomped!!

Destroy all those lines of evidence systematically and I will disavow this hypothesis. Come at me bro.



No we don't need a sabertooth mummy, we already have more than enough to sensibly conclude LARGE LIPS FOR THE WIN!!






Special thanks to the work of Jaime Headden and of course this post has the spirit of "All Yesterdays" (Naish, Witton, Kosemen) smeared all over it. Whether or not these researchers agree with my conclusions this work would not have been compiled without their existing works, thoughts, and efforts.

Also special thanks to the deviantartists who took a chance on depicting big lipped sabertoothed cats. I fully believe that your risk taking will end up on the right side of history.

P.S. This was just the warm up. I'm coming for ya' next lizard lipped theropods...

References

Ivory Identification Guide. USFWS. https://www.fws.gov/lab/ivory_defined.php Natural Ivory. https://www.fws.gov/lab/ivory_natural.php

Saliva - More Than Just Water in Your Mouth. EUFIC. http://www.eufic.org/article/en/artid/Saliva-more-than-just-water-in-your-mouth/

Enax, J., Fabrittus, H.O., Rack, A., Prymak, O., Raabe, D., Epple, M., 2013. Characterization of crocodile teeth: correlation of composition, microstructure, and hardness. Journal of Structural Biology 184 (2013) 155-163 link

Reisz, RR, Larson D. (2016) Dental anatomy and skull length to tooth size rations support the hypothesis that theropod dinosaurs had lips. unpublished abstract 2016 Canadian Society of Vertebrate Paleontology

Riviere, HL, Wheeler, HT. 2005. Cementum on Smilodon sabers. The Anatomical Record. 7 June
2005. 285A 634 - 642. link

"Night Terrors"Sinornithosaurus by Duane Nash

Making dromaeosaurids nasty again... Yes, there is a bit of a straw man argument in there because many might say they never stopped being nasty. But it is my straw man to make, tear apart, refashion, and burn to smithereens as I will... so while reading these posts on dromaeosaurids always keep in mind the tug of war between past and present interpretations scientific, artistic and popular. Don't forget as well these animals had a long tenure as small to medium sized predators so there is a lot of room for variation in terms of behavior, physiology, and appearance.

Something has happened to dromaeosaurids. They have went from jumping on the back of giant ornithopods to jumping on the back of opossums. They no longer look like the scaly, crazed, methed out gang overlords of the Mesozoic bestiary but instead dapper, attractive fashionistas that glided out of some Mesozoic audobon photo shoot. The psycho reptoid wolf-lizard of the Mesozoic is now the camera friendly fashion model of the Mesozoic.

Probably my favorite ol' school Deinonychus image credit William Stout

New school Deinonychus taking on smaller game in RPR model credit Emily Willoughby

A very attractive, dapper Deinonychus by Emily Willoughby. CC4.0

While the ol' school raptor I grew up with is now nothing more than a nostaligic memory ready to join the ranks of swamp bound brontosaurus I am not entirely at ease with all aspects of this new dapper "ground hawk" model for dromaeosaurids. Something just does not sit well with me.

First things first, the claw. Dat claw. Second to ol' sexy rexy and his chiseled and ruggedly masculine good looks the "killing claw" of dromaeosaurids and especially Deinonychus is probably one of the most emblematic and iconic elements of the theropod predatory arsenal. Are we focusing too much on the "killing claw" in terms of prey dispatch but negating other aspects such as the hand claws and teeth?

A brief review of several of the more pertinent works that have brought us to where we are now.

The Slashing Claw Denied...

While the youngins today have grown up knowing that the killing claw of these animals did not cut scythe like slashes through the hides of dinosaurian megaherbivores I do have to admit to feeling a pinge of let down in my inner fanboi when this was first revealed via the study "Dinosaur killer claws or climbing crampons"way back in 2005. Essentially what Manning et. al. did was build a robotic hydraulic Deinonychus antirrhopus claw and lower leg and attempted to drive it through a pig carcass. Instead of the meter long slashes of lore the results were a little underwhelming. The claw did puncture the carcass but as they attempted to drive it through the flesh tissue simply bunched together below the entry preventing a long slash wound.



In comparing the morphology of the claw they found it most lined up with the claws of climbing animals. Manning et. al. did not totally eschew the notion of dromaosaurids leaping onto the sides of megaherbivores but offered an alternative; the killing claw was now a crampon which allowed the predators to jump onto the side of prey and deliver slashing bites with the jaws.

Jumping on the Flanks of Giant Herbivores Denied...

Seems pretty legit right?

Well the next paper seemingly expunges the use of the claw in climbing onto the back of megarherbivores. Enter the Raptor Prey Restraint model (RPR) which probably needs little introduction to most readers here. Fowler et. al. reject the notion of dromaeosaurids latching onto the flanks of large herbivores and slashing at prey with foot claws or teeth. Instead prey subequal to the size of the dromaeosaur is pinned down beneath the weight of the predator; stability flaps of the "wings" and movement of the beam like tail help maintain an upright position; and prey is essentially eaten alive if it is not killed outright by the feet.


And you know... I like this a lot. It makes sense - there is a good analogy with modern accipitridae and it has a nice little thematic thing going on with the flight exaptation given that dromaosaurids are likely secondarily flightless. The authors also make a very striking contrast between dromaeosaurids and troodontids that suggests a degree of partitioning between the two groups. Dromaeosaurids had shorter but more powerful metatarsals suggesting a larger prey size seized by the feet than troodontids which compromised strength for cursorial ability and a quicker grip on smaller prey.

So ground hawk Deinonychus... what is not to love?

There are some caveats to this model that the authors address that I think warrant repeating:


So, despite the arguments in favor the RPR model for dromaeosaurids and the inherent attractiveness of the model it appears that dromaeosaurids were not >as good at it< as their modern avian counterparts. I am not saying RPR is not a thing and, again, this is from their own paper but it appears that a 50 kg Deinonychus is not equal to a scaled up 50 kg red-tailed hawk in terms of relative grasping power of the feet. Furthermore if you look at the vice like grip that modern raptors can enact in which digit I is rotated completely opposite the other three digits it appears that Deinonychus and other dromaesaurids do not fully rotate the digit opposite the other three for a truly powerful vice like grip.

credit eaglesohio

Again, not trying to imply that RPR is not a thing for dromaeosaurids or that they did not pin and even kill prey with their feet but let us be clear with what the science shows as of now. In dromaeosaurids the RPR model is a relatively less powerful and less efficient version than modern raptors essentially due to the anatomical concessions of retaining some cursorial ability. But I am sure it was still unpleasant...

Actually what dromaeosaur foot graspers remind me of is cats claws and paws (gasp!! mammals). No really... anyone who has had a cat "knead" on them (i.e. breadmaking) knows what I am talking about. As the cat's claws clench shut in a semi-opposable fashion the claws actually pin stuff against the lower arm. In dromaesaurids grasping things would be pinned against the bottom of the metatarsus. This is still a pretty good grip and with both legs working together likely very efficient.

Dino Kitty

The Role of the...
ArmsWings?

I am obviously not the first to ponder this and it is a perplexing issue in many, if not most, predatory theropods - but what were the clawed wing/arms of dromaeosaurids good for anyway? Fowler et. al. posit them as dynamic stabilizers that combined with the fully feathered tails (like Archaeopteryx not Caudipteryx plumes) allowed these predators to maintain vertical superiority via flapping over prey caught in the foot claws. I like this a lot. So please don't misquote me when I argue that there is something to augment this method not completely replace it.

Those big hand claws seem like such a waste if all they did with their arms is use them in stability flapping.

Issues have been raised as far as the practicality in using the hand claws to grasp small prey dexterously or even bring the hands together to grasp small prey with precision. I honestly don't know what the current thinking on this issue is - or if there is any consensus at all? I would love to hear thoughts and input in the comments section... From what I gather on my cursory research things seem a little equivocal. The wikipedia page on Deinonychus mentions papers that support grasping and others that bring forth some practical questions. Some observations that cause me to question fine tune grasping of small prey items include the potential issue of the "wings" getting in the way of each other when brought together. Also and this is my general observation of patterns in clawed grasping animals: it seems reasonable that in order to achieve a powerful and concise grip that the digits and claws work better aligned in a similar plane. Essentially when you look at the grasping claws of a felid, modern avian raptor, or hell... even our own hands what you see is the digits not varying tremendously in terms of length and that they line up together relatively closely when clenched.

credit John Conway. Deinoncyhus (L) Archaeopteryx (R) CC3.0

Allosaurus hand. credit Domser CC3.0

For these and other reasons I find  "fine tune grasping of prey" hypothesis more than wanting. Enough so that other hypotheses warrant exploration.

The hypothesis I will offer - not sure if this idea has been explored yet anywhere to tell you the truth - is going to highlight exaptation of the flight stroke and musculature of the maniraptoran arm to a high degree. This is consistent with the strong hypothesis put forth by Gregory S. Paul that dromaeosaurids are secondarily flightless.

The clawed wing arms of dromaeosaurids could potentially act as clawed battering tools that would further bludgeon, wound, and traumatize prey and/or competitors especially that have been pinned by the feet.

Why not? The arms were strong, long, and heavily clawed after all. More so modern birds just love to bludgeon and smack other things around with their wings. Made famous in a series of posts at Tet Zoo(here 1, part 2, part 3, wrestling birds) by Darren Naish, some wings even have weaponized claws, clubs, and spurs. Dromaeosaurids - likely being secondarily flightless - already had the exaptation to use their wings as bludgeoning tools. All the musculature was already set up for it.

Two Deinonychus have a disagreement. Provided by Robin Liesens (Dontknowwhattodraw94)

As I mentioned earlier the study by Fowler argued quite well that dromaeosaurids were not >as good< as modern raptors in terms of prey dispatch via the foot claws. Other tools might be needed for prey dispatch... Why not use those nice hand claws powered by the incipient flight stroke to further gouge, pummel, and weaken prey that is being grasped by the footclaws and jaws? Not saying stability flapping did not happen just that stability flapping used in conjunction with with wing pummeling might have some merit. Furthermore the need to maintain vertical position over prey might be just a tad overstated - don't forget the fighting dinosaurs!! After all dromaeosaurids had a little bit more liberty in terms of getting down and dirty on the mat as opposed to accipterids which always have to be mindful of getting grounded with a serious wing injury.

CC 2.0 credit Yuya Tamai. Protoceratops & Velociraptor

And modern birds do love to fight and 'rastle!!


Did you check out that eye gouge at about 1:03? Note how right above the eye is nice a ridge of brightly colored, caruncled tissue... remind you of a suggestion I made before?


Or the above video which actually doesn't feature a stork eagle fight but loads of domestic breeds battling one another (uuurgh there Nash goes with domestics again). Loads of fleshy caruncled faces, face biting, wing pummeling, talon thrusting. In short very awesomebro!! but not necessarily without merit just because it is awesomebro!! You see the pattern - lunges and strikes are made with the head and/or feet. When brought into the line of fire of the wings, pummeling commences.

Tsaagan dispatching Velociraptor. work in progress Duane Nash

This methodology of prey capture/combat is essentially a bit of an inverse of a common tactic used by felids. Anyone who has a pet cat  (or who has a cat that has them?) should be familiar with it. If not simply stroke the vulnerable belly of a said felid and the forelimbs and/or jaw will lock into your arm and the back legs commence clawed kicks. In dromaeosaurids it would be the hindlimbs and jaws locking prey into place and the forelimbs delivering blows and trauma via wing pummeling.

Deinonychus wing pummeling Zephyrosaurus. credit Robin Liesens (Dontknowwhattodraw94)

In addition to the analogy to modern bird wing pummeling the analysis of theropod stress fractures and forelimb avulsions (Rothschild et. al., 2001) came up with some interesting results with regards to Deinonychus limb use: 43 hand bones and 52 foot bones were examined for signs of stress fracture - none were found. However the second phalanx in the second toe (the killing claw) has a healed fracture (YPM 5205). Why is this important? Well it suggests that the hand claws are not hooking into things and holding them tightly such as appears to be the case with Allosaurus which shows multiple manual pathologies - but the healed killing claw suggests that digit II is hooking into and holding struggling prey/combatants to a higher degree. On the other hand it is worth asking why wing pummeling would not create stress fractures? Perhaps with the force being distributed across the whole surface of the wing (including the feathers) stress fractures would not be such a problem? Are stress fractures a problem in modern birds that wing pummel? Could be an avenue of exploration...



Really I am quite surprised that wing pummeling in dromaeosaurids (and other winged dinos/maniraptorans) has not been proposed before... I mean has it? I dunno, can't find any mention and it seems like a pretty logical inference from what I have gathered.

Two potential criticisms I want to address:

"Yes but modern birds use this wing pummeling in antagonistic disputes not predatorial. Birds of prey do not batter their prey with their wings."

True. Remember Fowler quite convincingly argued that dromaeosaurids were not  as relatively >strong< in grasping as accipterids. Does this imply that they were small game specialists? I think not. My contention is bolstered by the "fighting dinosaur" specimen. You will hear some researchers try and explain this situation away as a "rare" or "aberrant" exception to the "baby killer specialist" or "small prey only" model. With all due respect I think that they are mistaken. Not that loads of baby dinosaurs were not munched on, merely that dromaeosaurids and most theropods were not "specialized" for that task.

Given that dromaeosaurid foot grasping was meh compared to modern birds of prey but they were still getting into the thick of things with some pretty rugged combat other lines of attack should be invoked. Those big hand claws seem awfully put to waste in mere stability flapping. Especially when attacking strong retaliatory prey like protoceratopsids.

"Why don't birds of prey pummel prey with their wings?" As I alluded to earlier accipterids differ from dromaeosaurids in that they are dependent on flight. Wing pummeling for them may be selected against as a predatory strategy because they risk an injury, not to mention their feet do the job just fine.

"What about the claws getting stuck in the flesh and skin of the prey during pummeling. Could that be a problem?"

I don't think so. If the downstroke can enmesh the claw in the animal then the upstroke can pull them back out. If claws getting stuck in stuff was so much a problem I guess that implies these animals could not use their claws to climb and clamber in trees as well, because their claws would get stuck in wood, amirite?

Given that; dromaeosaurids are likely secondarily flightless; that their digit morphology is aberrant from other predatory "graspers"; that wings may have got in the way of grasping, especially of objects on the ground; that the fingers remain spread during flexion; that one handed clutching of objects to the chest is just weird; that the elbow can not be fully extended and forelimb mobility is limited;  that extant aves often use their wings - sometimes coupled with knobs, spines, and claws - to pummel other animals; for these reasons I posit the hypothesis that clawed wing pummeling is a promising tactic used in dromaeosaurid predatory, combative, and defensive endeavors.

At the moment I see no reason that the idea of wing pummeling can not be extended to other winged dinosaurs and maniraptorans. Hello wing pummeling Gallimimus, Gigantoraptor, Therizinosaurus, and Deinocheirus!!


Next up: biting, scavenging, scrumming, and bone cracking dromaeosaurids.



References

Fowler DW, Freedman EA, Scannella JB, Kambic RE (2011) The Predatory Ecology of Deinonychus and the Origin of Flapping in Birds. PLoS ONE 6(12): e28964. doi:10.1371/journal.pone.0028964

Manning, PL, Payne, D, Pennicott, J, Barrett, PM, Ennos, RA (2006) Dinosaur killer claws or climbing crampons. Biology Letters (2006) 2 110-112 pdf

Rothschild, B. Tanke, D, Ford, TL (2001) Theropod stress fractures and tendon avulsions as a clue to activity. Mesozoic Vertebrate Life. editor Tanke, D & Carptenter, K. Indiana University Press pp331-336

Senter, Phil (2006) Comparison of forelimb function between Deinonychus and Bambiraptor (Theropoda: Dromaeosauridae). JVP Volume 26 Issue 4 2006




As I have seen an uptick in traffic and subsequent comments that lower the standard of conversation on this blog I will be moderating the comments section from here on out. I don't have a comment policy other than it is my blog and I will do whatever the hell I want to with it and ban whoever and whatever comments I want. Disagree with my ideas - fine, disagree with me so strongly that you launch smear campaigns and rants against me... fine... go make something original on your own. You will still be banned here.  As several recent commentators now are - banned for life. It should not be too hard to find out who those are from recent posts as I will leave their comments up as fair warning to others.

There is a big ol' internet out there and I don't need you.

Over all though I am happy with the input, differences of opinion, and general intelligence of the commentators. You guys are my "peer review" as much as I can muster at least and have helped me change and refine my own thoughts and perspectives numerous times. Keep it up.

Sorry if you thought that theropod lip post was happening now, a little bait and switch hahaha... some other stuff beforehand that is very interesting to build suspense...  but I am still coming for ya' lizard lipped theropods.

Scavenging gets no respect. There is a reason you don't see hyenas and vultures put on coats of arms or have sports teams named after them. Lions and eagles yes, but never vultures and hyenas - ironic that all of these animals do scavenge (and hunt to various degrees). Doubly ironic is that in carcass disputes it is often vultures and hyenas driving the eagles and lions off of carcasses. It is a pet theory of mine that  what makes an animal an exquisite and refined hunter often works against them in carcass disputes. Because the refined hunter depends heavily on preserving the physical armaments that allow it to do its job it is at a disadvantage compared to more generalized opportunistic competitors who can be more reckless in battle. To make the sports analogy it is the difference between the tactical and technical boxer whom excels in the specific and controlled environment of the boxing ring and the unrefined street brawler. The highly skilled and nuanced technical abilities of the boxer will win the day over the street brawler in the ring for sure. But take this tactician out of the ring and into the street against the brawling street fighter - who fights dirty, uses bluff and swagger, and can simply take chances with regards to life and limb that the professional boxer can't - and the outcome swings in favor of the brawler. What makes a good street fighter work well is a different skill set than what a boxer has and what makes a good scavenger work well is a different skill set than what a specialized hunter has.

Cue youtube videos:


Note how the tawny eagle just can't hang with the vulture hordes. A better hunter the eagle definitely is - but a better brawler than the vultures? Sorry the eagle just can't bang with the vultures.


Of course I have to include a clip of my hometown hero the California condor displacing the largest eagle of North America the golden eagle. "Step up to me Mr. Eagle?!? Pwwwfff my ancestors used to go to toe to toe with teratornids over mammoth entrails! Go hunt some rabbits!!"





Don't forget to include mention of the epic dominance of cinerous vultures (sometimes called Eurasian black vulture not to be confused with the New World black vulture) Aegypius monachus which often usurps the golden eagle.



Were dromaeosaurids more the vulture or eagle in carcass disputes? Given that dromaeosaurids did not rely on flight to hunt and may have been afforded wing pummeling; that they were literally armed from head to toe in terms of combative weaponry; that they were good sniffers; that we have evidence very suggestive of scavenging; and the ecological imperative to do so; dromaeosaurids were likely very good facultative scavengers. Yeah, so I lean heavily towards more of a vulture than an eagle in these animals. Both in appearance and demeanor.



Taking the theme that I started with on my last post - an over reliance of the import of the "killing claw" in all endeavors dromaeosaurid and refining the dominant RPR model of a "ground hawk" dromaeosaurid - I am going to expand on that in terms of how and why dromaeosaurids were very good, capable, and successful facultative scavengers. The caveat being, I should just explicitly state, that this does not imply a lack to or unwillingness to hunt. But one more thing about that hypertrophied second digit - the "killing claw". It seems several vultures sports such an enlarged second digit - the magnificent cinerous vulture (Aegipius monachus) and the red-headed vulture (Sarcogyps calvus) pictured below.

red-headed vulture (Sarcogyps calvus) credit Dibyendu Ash CC3.0

cinerous vulture (Aegypius monachus) CC3.0 credit Mistvan

Enlarging the toe on the second digit serves a useful purpose in pinning meat down which allows the beak and head to get leverage in pulling bites off. The "killing claw' in maniraptorans might have been used just as much if not more in leveraging good bites while scavenging/feeding as opposed to outright "killing". Additionally the line of action on the dental serrations suggests that the denticles on the back end of the tooth - the lingual side - were doing most of the cutting work as the animal pulled back on food items. It really is all about the teeth and jaws anyways...

Achillobatar scavenging ankylosaur Talarurus by Duane Nash

Ecological practicality of terrestrial scavenging; optimal size; factultative vs. obligate terrestrial scavenging

First things first. The issue of ground based scavenging. We have all heard the argument "you can't have an obligate ground based scavenger because there simply isn't enough carcasses to sustain such an animal". Sounds reasonable enough and this was one of the trump arguments used to disavow the scavenging T. rex hypothesis. Is there a way to test it?

Some researchers recently did just that in a particularly ingenious and creative manner: Body size as a driver of scavenging in theropod dinosaurs (Kane et. al., 2016). Under various conditions of carcass detectability, carcass size, and competition they performed basically a SIMS version of let different sized theropods find dead stuff and see what body size pans out to be the most efficient in terms of cost/benefit analysis. Basically if you are looking for carcasses to supplement your diet the results are congruent with the assertion that only soaring scavengers can make a total living off of scavenging. Both small theropods and large ones had difficulty earning enough calories from facultative scavenging to make the activity worthwhile. If we think about the issues faced by both very small and very large theropods in terms of garnering benefit from scavenging this makes sense. Small scavengers can't cover as much ground and are easily displaced from carcasses. Large theropods - although they can dominate a carcass - have to move all that weight around and by the time that they detect and reach a carcass much of the available calories might already be consumed by smaller and more numerous scavengers.

What the researchers came up with is very interesting in terms of optimal body size for a land based scavenging theropod. There appears to be a mid-sized sweet spot. Small fry like microraptorines didn't do so well and at the other extreme multi ton giants like tyrannosaurids and carcharodontosaurids did not fair too well as facultative scavengers. Facultative scavenging is most optimal in terrestrial theropods in a size range of between (they get pretty specific) 27 and 1,044 kilograms.

Dromaeosaurids slot into that size range very nicely you should note.

While I have read of several people poo-pooing this paper and its conclusions I personally find a lot of merit (with some caveats of course) in this methodology and the conclusions reached. At the lower end of the size scale I would think that Velociraptor and Dromaeosaurus would still  fair pretty well even though they are lower than 27 kilograms. Jackals and coyotes do pretty well as factulative scavengers and they are a bit smaller than 27 kilograms. Additionally at the higher size range let us keep some perspective. Imagine just >one< 50 ton sauropod died in an ecosystem with several multi-ton theropods and loads of smaller and immature theropods. Chances are the big theropods could locate, dominate, and feast on that sauropod for a while. Their large size and relatively slower metabolism might allow them to scarf down a load of meat that sated them for several weeks or even months. So the big boys might scavenge less frequently but when they do dominate large carcasses that glut of food might form the bulk of their caloric intake for quite a while.

Not to mention this paper completely jives with the conclusions of a similar paper that came out in 2011 that has gone a little overlooked... when two independent studies reach similar conclusions that should perk your interest. The 2011 paper is called Intra-guild competition and its implications for one of the biggest terrestrial predators, Tyrannosaurus rex (Carbone et. al. 2011).

Here is my favorite excerpt from the results:



Physical evidence suggestive of scavenging

Dave Hone has written a bit on Velociraptor consuming and - in his interpretation - likely scavenging azhdarchid pterosaurs  here and here. Make sure to go back and read the commentary it is hardly a close and shut case of scavenging. Hone makes a more compelling case for Velociraptor scavenging a hefty size Protoceratops "fighting dinosaurs", part II. Hone also has some papers on the topics but they are not open access, shucks. The blog posts and commentary get the point across though.

credit Brett Booth

Phil Currie and colleague (1995) also describe another azhdarchid consumed by a velociraptorine theropod but don't conclude it was scavenged.

I don't fully agree that the idea of a velociraptor taking down a 2-3 meter wingspan pterosaurs is nonsensical so for me that is equivocal proof of scavenging. However the scraping of flesh off the jaw of the large Protoceratops is a more compelling argument for scavenging.

Additionally you have the famous Yale Deinonychus and Tenontosaurus quarry that might indicate not only scavenging but aggressive intraspecific killing and cannibalism among Deinonychus. And who knows what surprises await us with the new Utahraptor block James Kirkland and co. are working upon...

Roach and Brinkman (2007) advocate a "diapsid like" foraging strategy in Deinonychus and other theropods as the best and most parsimonious null hypothesis. They eschew the notion of cooperative pack hunting posited to bring down herbivores that are several orders of magnitude larger than the theropods but instead highlight scavenging, combat, and cannibalism as the likely culprits that resulted in the taphonomic signal from the Yale quarry. Chief among these is the presence of articulated tails in the quarry the argument being that the bony and tendonous tails were eschewed in favor of more meaty pieces that were hauled off. I do agree with a lot of what they are selling. They do leave the opening for opportunistic group foraging where a congruence of factors might lead to a "mobbing" type foraging scenario. We see this with sharks gathering escorting ailing whales along and literally eating them alive. Or crocodiles gathering at choice feeding situations or latching onto the same prey animal or loosely "cooperating" to shoal prey together. I would also extend this to the manner in which vultures gather around a carcass and use strength in numbers to harass and intimidate other predators off a carcass.

The blog post Raptors: Do They Live up to the Hype (part 2)? Goes a bit further into the Deinonychus saga if you want to go further...

My purpose here is not too weigh too heavily on whether each of the above scenarios are unequivocally evidence of scavenging but merely highlight that there is a body of evidence that points heavily in the direction of scavenging in dromaeosaurids.



On Hell (Creek) Patrol With Dakotaraptor

Few stories in dinosaur paleontology were as exciting and celebrated as the revelation of an honest to goodness mega-dromaeosaur in Dakotaraptor (DePalma et. al., 2015) that inhabited the latest Cretaceous of North America right alongside good ol' sexy rexy. Met with a flurry of fanfare and fan art I decided to let the dust settle a bit before giving this beast the antediluvian salad treatment.

Any epic beast needs a suitably epic soundtrack to go along with it - Judas Priest's Hell Patrol:




There are a few points from the paper on Dakotaraptor that have not received enough attention in my opinion. Specificities that really speak to the adaptations and ecology of an animal that should garner much attention.

Dakotaraptor Is Cursorial

Interpretations of Dakotaraptor that highlight the ecology of this animal as a cryptic, stalker of closed habitats - the "ghost of the forest" scenario - are missing the story that the bones are telling us. This animal was leggy, it was cursorial, and in life it would have departed strongly from the more low slung and slower Utahraptor or Deinonychus.

credit taphonomy CC4.0

I mean just check out those legs!! Keep in mind that this critter was having to go toe to toe with ridiculously leggy young T.  rex and you can imagine the evolutionary imperative to get speedy. Dakotaraptor appears to have made the necessary concessions needed to increase cursorial ability.

As I discussed in my last post there are certain compromises to be made in terms of raptorial grasping abilities in these animals versus cursorial ability as highlighted by Fowler. To review as grasping ability increases the metatarsals shorten for better leverage and strength but running ability is compromised; conversely as cursorial ability increases grasping strength decreases. Also bear in mind that all dromaeosaurids/maniraptorans were relatively weaker than modern raptors in terms of grasping power of the feet - they were not simply overblown red-tailed hawks.

An Interesting Incongruity

If you followed my articles on Spinosaurus and my argument for underwater punting in that animal you  know that I do have a fondness and attraction for anatomical incongruities; two things combined that seem to make no sense but when analyzed in a different light actually offer a more refined animal. In Dakotaraptor we have such an incongruity.

Digit II is hypertrophied. The "killing claw" in this animal lives up to all the hype. Not only is the claw relatively large, the attachment for the muscle and tendons that drive it - the flexor tubercle - is robust. Whatever way in which this animal was using its digit II it is obvious that it has invested heavily in it.

However the incongruity is seen when we move out to digit III and IV where the claws on those digits are not highly recurved nor is there a significant flexor tubercle present. In fact the flexor tubercle is so reduced in those digits to be pretty much non-existent!!

credit Taphonomy CC4.0 arrows point to flexor tubercle in foot claws Dakotaraptor

I mean just look at the contrast in the flexor tubercle attachment in these two claws. For me this is a compelling argument that the classic raptor prey restraint model posited for these animals is lacking. Dakotaraptor was moving further away from grasping things with its foot claws yet at the same time digit II was still large and strong. What is going on here?

Going back to my earlier bit on the cursorial aspects of this animal and resolving its place in the ecology of the environment in which it lived proves useful I contend. Several inferences are useful in giving better precision as to how this animal likely operated.

Inference 1Dakotaraptor was highly cursorial.

Inference 2Dakotaraptor - at least in the adult morph - was fairly limited in arboreal capacity. At best they were probably very clumsy in trees due to large size, long legs, and limited foot strength.

Inference 3 Lesser dromaeosaurids, azhdarchids, and tyrant lizards - especially juvenile and rapidly growing teenage rexes - created an especially quarellsome predatory and scavenger ecology. All of these animals would have been usurping, competing, and fighting over carcasses. Azhdarchids, juveniles rexes, dromaeosaurids, and Dakotaraptor all slot into the ideal size niche to be successful facultative scavengers.

Inference 4Dakotaraptor could dominate pterosaurs, dromaeosaurids, and smaller rexes. However because it could not dominate larger immature rexes - which were still very cursorial - Dakotaraptor itself needed both speed and maneuverability to evade these animals as it was likely not highly arboreal.

Inference 5 The enlarged and robust ungual and claw in digit II primarily aided in combat - especially in competitive skirmishes over carcasses - and assisted in pinning meat down as the teeth, jaws, and neck pulled bites away from the animal (alive or dead). The denticles on the teeth of Dakotaraptor are most defined on the rear (lingual) side as they are in other dromaeosaurids supporting this notion, The RPR restraint model appears less important in this animal relative to other dromaeosaurids in prey capture. Instead digit II could primarily be used in combative endeavors while wing pummeling and the teeth and jaws did the actual killing.

HellPatrolDakotaraptor by Duane Nash

Dakotaraptor may just be a very specialized and rare component of the Hell Creek hunter/scavenger guild. It was large enough and well armed enough to drive off everything but the larger rexes from a carcass. The cursorial adaptations speak to an animal that could cover a lot of ground to find carcasses, prey, and evade larger competitors if need be. In short we see a lot of compromises that facilitated the existence of a sometimes hunter often times scavenger. It was big, but not so big that scavenging became impractical. It was well armed with a massive and powerful digit II but compromised the raptorial abilities of the other digits in favor of cursorial adaptations. The forelimbs were large, feathered, and powerful - great assets for combat, display, and intimidation. In many ways the large and rare Dakotaraptor was possibly like the lappet faced vulture of Africa. Large and strong enough to dominate most other scavengers at a carcass but would step aside for the larger tyrant lizards just as lappet faced vultures dominate other vultures, marabou storks, and jackals but move aside when hyenas show up.

Wings Suggested as Dominance Display

As in my last post on wing pummeling I will get behind another spotential behavior for dromaeosaurid wings that gets surprisingly scant attention - dominance display.

credit Christine Lamberth blog

Such wings could be spread wide over carcasses in order to appear large and more dominant over competitors. Indeed this is the classic show of dominance modern carcass rendering birds (vultures, raptors, petrels) display at carcass disputes. Wing display for intimidation is so painfully obvious I can't believe that such suggestions don't get more attention. I have heard of it before so I can't claim to be the first to suggest it but I am definitely in favor of it. When we look at what modern carcass disputing theropods do with their wings... you have heard that story before though.

Such a shame that vultures do not get the recognition and respect they deserve for their role in modern competitive ecosystems; that they are spiralling into extinction; that they are not posited as the go to analogy for how extinct theropods looked, behaved, and operated when rendering carcasses - despite the fact that, quite simply, they are the modern theropod that does such things most often. Instead grumble, grumble flipping venomous lizards for crying out loud. Venomous lizards.

When you are watching a scrum of vultures feeding you are witnessing a direct portal into to the feeding activities of dromaeosaurids and other theropods in the Mesozoic's past. The theatrical displays; the spread wings; the fast jerky bites; the constant fight for dominance and hierarchy; and, most importantly, the constant and non-stop flurry of motion, action, and violence. Such scenes would be enacted on a much larger and grander scale in the Mesozoic. A difference of degree but not type. A sight both startling and jaw dropping.

lappet-faced vulture and white backed vulture scavenge elephant carcass. credit Chris Fallows CC2.5

Coming up: restoring dromaeosaurids, ugly vs. pretty, and a new hypothesis on dromaeosaurid biting technique!! 

P.S. I will talk of the weird "tail plume" I depicted on the Dakotaraptor in my next post too so don't even ask about it.

References

Carbone, C., Turvey, S.T., Bielby, J. (2011) Intraguild competition and its implications for one of the biggest terrestrial predators. Proceeding of Biological Sciences. Sep 7(278) 1718 2682-2690. online here

Skeksis (singular and plural) Antagonists from Jim Henson's 1982 film The Dark Crystal. Concept artist Brian Froud conceived as "part reptile, part predatory bird, part dragon".

Appearance (from wikipedia):

The Skeksis are tall bipeds combining avian and reptilian characteristics. They wear elaborate but threadbare robes of lace, velvet, and brocade which apparently keep the skeksis' constantly decomposing bodies intact and make them look larger and more intimidating. Their heads are beaked like a vulture's but simultaneously sporting curved fangs. They have enlarged bellies and long reptilian tails, as well as curved quills on their backs. They have two pairs of arms but only one functional the other reduced... despite their frail appearance they are powerful creatures.

It should be no great revelation that this post will serve as the most subjective and probably therefore most controversial in this series. Experience in electing novel soft tissue structures in T. rex and Smilodon has  taught me that much...

It should also come as no surprise to readers that I am no great fan of dapper dromaeosaurids - a look that has come into vogue in recent years.



Dapper /'dapper/ adjective (typically of a man) neat and trim of dress, appearance, or bearing.

Deinonycus antirrhopus credit John Conway CC3.0

How did this look evolve? It is not too hard to trace a lineage of inspiration from Gregory S. Paul who retooled dromaeosaurids as feathered and decidedly bird like to John Conway who took a lot from Paul's look and made these animals even more birdy to Emily Willoughby one of the leading contemporary dromaeosaurid paleoartists whom has greatly inspired the dominant ground hawk look.

Acheroraptor credit Emily WilloughbyCC3.0

A commonality in all three of these artist's look is the clean cut juncture on the facial region separating feathered from non-feathered parts. This clean cut visage, almost always combined with an attractive feathery countenance lifted from a modern bird of prey (red tailed hawks and peregrine falcons are common suspects). A look that has been consistently aped and imbued itself into the dominate appearance of these animals in paleoart.

Peregrine Falcon credit Magnus Manske CC2.0

Gregory S. Paul hypothesized a "proto-beak" around the mouth of his dromaeosaurids and other maniraptorans. Basically an area free of integument and slightly cornified. See here and here. Essentially it was an inference made on the perceived - and correct - relatedness to modern birds.

The problem is that we do not have any evidence of a proto-beak in dromaeosaurids or any predatory maniraptorans at all for that matter. Nothing, nada, nunca. Nor do we have any evidence of the type of clean cut juncture depicted by Conway & Willoughby which has influenced current depictions.

Mathew Martyniuk discussed this seldom mentioned meme in an excellent post The First Feathered Dinosaurs (In Art):

"Paul essentially invented the latter meme (half feathered faces) in an attempt to make his theropods look more bird like (by suggesting a sort of beak), and while this was his own speculation, many later artists ran with it, including in early drawings of Sinosauropteryx."

While Conway's and Willoughby's renderings do not necessarily imply the sort of "proto-beak" structure that Paul hypothesized both of these artists kept the clean cut dapper "featherline" which Paul used demarcating a solid break from the feathered region of the head and the bitey jaw region. This trope has imbued itself into countless depictions of dromaeosaurids since, to the point that it is in many ways the de-facto way to depict the heads of these animals in many people's minds. Just remember - if you chose to depict dromaesaurs this way you are merely inheriting a trope that has no basis in evidence of either a proto-beak or a defined juncture between feathers and non-feathery covering on the heads of these animals. Not saying it is impossible that some dromies did not have such a juncture just that it is based on a hypothesis of a proto-beak which has not been borne out evidence wise but remains with us as an attractive speculation.

Indeed feathers covering the entirety of the head (except maybe the nostrils left open ala mammal noses) is what might be the more parsimonious interpretation as suggested by Sinornithosaurus and Zhenyuanlong. With no evidence of a proto-beak in these animals there is no reason to assume feathers did not go all the way to the oral region.

Sinornithosaurus'Dave' credit DinoGuy2 CC1.0

This actually opens the doors for a lot more play as goes the facial appearance of these animals. As it should be, because we should not expect a lineage of animals that evolved and lived in diverse conditions for over 100 million years to all look a like. Everywhere from fully feathered to yes, naked skin, or in between.

"Go Away" by Lucas-Attwell w/permission Tsaagan mangas. deviantart

You know I loves me some vulturine inspired dromies. I really like how the tail display, arm-wings, contrasting white/dark colors, and jaw are all used together in threat display. As I argued in my last post there is at least as much - if not more - to glean from vultures as analogues to many dromaeosaurids as there is from raptorial accipterids. Also note that the feathers are plumaceous like in an ostrich not the stiff venaceous feathers we have often seen in paleoart.

Tsaagan. credit Matt Martyniuk CC2.5

I am a little surprised at the blowback I receive in electing naked headed, gnarly faced, caruncle ridden dromaeosaurs as a likely look for many of these animals. But why not? I am fully willing to concede my bias for ugly, uncouth, goblin looking critters duh.... I wear my inspirations on my sleeves baked in bong hit residue, blotter acid, splatter films, and swedish death metal. That does not mean I am in fact wholly wrong. More to the point, I would suggest others are less open than I am in conceding their own biases. Do I suspect that some people really have a penchant for the attractive, elegant, and refined look of dromaeosaurids that has come into vogue? Essentially a grounded peregrine falcon or red-tailed hawk? That such elegant, attractive, and appealing visages have a conscious or subconscious appeal to many of the artists and fans who endorse such a look even going so far as to assert "this is how they looked, period". Wrapped up in a nice little bow because of the RPR hypothesis - which as I have mentioned again and again Fowler stated specifically dromaeosaurids were not as strong graspers as modern accipterids - fueling the typological thinking to dress up a Deinonychus as a grounded red-tailed hawk? And that people who have such a definite and emotional attachment to such a look would be dismissive and threatened by my interpretation asserting a more vulturine influence? Nah, that never could happen snark, snark...

Just to keep in mind I am getting my inspiration from birds too, and not all birds are concerned with looking regal and elegant...

For every grey-crowned crane I can raise you a helmeted hornbill;

helmeted hornbill. Rhinoplax vigil Doug Janson CC3.0

For every great blue heron I give you a marabou stork;

Marabou Stork (Leptoptilos crumeniferus) credit Rusty Clark CC2.0

(end of rant)....



Truth is we do not have a lot to go on in terms of facial appearance of the medium to larger dromaeosaurids that lived in open and/or hot & arid environments. Painting with broad strokes I would lean more towards fully feathered heads for smaller dromies/small game specialists especially in closed temperate environments - essentially Liaoning. But for dromies that were out in the open, fighting and competing over carcasses, going toe to toe with carchs, abelisaurids, and tyrant lizards, in hot and/or arid environs a naked head with fleshy adornments is a defensible position. Many of the more famous dromies such as Velociraptor, Deinonychus, Utahraptor, and Dakotaraptor fall in this category.

credit Charlie Hamilton Jones Getting Cozy With Vultures

Large exposed patches of skin on the head and neck can serve a thermoregulatory function and also social signaling. Blood can be flushed into caruncles, necks flaps, and other skin adornments in colorful threat dominance displays as occurs in condors.

Andean Condor credit Kevin Law CC2.0

Whenever I talk about fleshy skin adornments on theropods - including large lips - there is a consistent critique that people chime in with: "but these areas would be targets for biting by conspecifics and get snipped right off!?!"

Let me offer some rebuttals (takes a deep breath):

1) Losing a chunk or flap of skin is still preferable to losing an eye or getting a bite on the neck or vertebral column which could have fatal results. That being said skin can be amazingly strong, elastic, and (best  of all) it grows back. Hyenas, bears, badgers and yes vultures are often noted for the strong and elastic properties of their skin that allow them to suffer abuse that would seriously lacerate lesser skinned animals. Theropods - and especially combative dromies - had all the reason to not only have such thick and elastic skin but abundant skin derived display structures. Just look at the skull of a male andean condor, there is no tell tale osteological signifier that it looked like the mug above.

2) Which brings me to my next point. We already have compelling and irrefutable osteological evidence of display structures on other theropod skulls (Dilophosaurus, Guanlong, Monolophosaurus etc. etc.). That these animals would grow such features in a highly visible and vulnerable part of the body complete with thin struts of bone - and they were not snipped right off - is all the more compelling reason to suspect a more widespread and outlandish panoply of soft tissue structures throughout theropoda (and many dinosaurs in general) that would not preserve. Especially among those theropods that were regularly coming together socially at large carcasses in feeding events/social gatherings. Dromies certainly count in that regard. In fact we should predict such structures.

3) Which leads right into my next point - prediction met (sort of) !! By now many readers have doubtless heard of the (as yet undescribed) evidence of a large distensible gular neck structure on a Tarbosaurus bataar. If this story pans out we do have evidence of a fleshy display structure on a lineage of the most bitey theropods of all time in the most vulnerable part of the body. So putting a highly visible, likely brightly colored display structure on the neck of the most powerfully biting terrestrial tetrapods of all time still panned out in the Darwinian struggle.

4) Such critics have probably never really been in a fight or done poorly in one... really don't take it as an insult because fighting and violence in humans is not really a good trait to endorse. But looking at what professional fighters and strikers do and the tactics that they use can be useful. One common tactic  used in boxing is to intentionally offer up a shot that puts your opponent in a vulnerable position by feinting a move and then counter-striking.  Let's go through what happens when a "vulnerable" fleshy skin adornment (or large lips) are bitten by another theropod.

I In a dispute one theropod bites the skin flap on the chin of another theropod. Due to the strength and elasticity of this skin it is not simply cleaved right off but instead substantial yanking and pulling would be needed to remove such structures.

II As the theropod that did the biting - let's call it theropod A - pulls and yanks that piece of skin off the bitten theropod - theropod B - and finally cuts clean the skin structure the momentum of the pull off will move theropod A downward and lateral from theropod B.

III At this point it is theropod B - the bitten theropod - that has tactical advantage. Theropod A in the course of yanking off a chunk of skin has put its head and neck inferior to theropod B.

IV Theropod B can now attack theropod A and get a potentially fatal or devastating bite to the back of the neck or head of theropod A. More importantly theropod A can not retaliate when bitten from this position at the back of the neck/skull.

V Theropod B has lost a piece of skin that can potentially grow back. Theropod A has in its miscalculations put itself in a vulnerable position and although it successfully inflicted non-fatal damage by removing a chunk of skin it may potentially lose its life because in doing so it left the back of its head and neck open.

"Bite my lips I dare ya'" credit Tiia Monto CC4.0

Watch brown bears fight. Their big, jangly, fleshy lips are mere inches from one another yet they are not targeted. Because bears are better tactical fighters than most people. Bears know better than to commit to a non-fatal attack that might leave them open in the end.

One final word on theropod facial biting/skirmishes. I suspect the vast majority of bites were not the bone scraping/puncturing potentially fatal traces we see in the fossil record. The overwhelming majority of interactions that went beyond theatrical displays and gesticulations were probably the fast little nips and non-committal bites we see among canids and social feeding birds. Many of these bites would not even break the skin.

Ruppels Vulture bites another, showcases tough, elastic skin. credit. credit Charlie Hamilton Jones. natgeo

I will delve more into display structures in theropods in the future because I think that they are a fascinating topic for exploration. Instead of asking how much or how little these feature were found in theropods - as you can tell I suspect that they were quite widespread - I think we should be asking why are mammalian predators (and I guess you can extend this question to predatory monitor lizards) so impoverished when it comes to display features?

A Long History Of Dromaeosaurid Evolution Lots of Room For Variation

If we accept a middle Jurassic origin for dromies of about 167 mya that gives us more than 100 million years of dromaeosaurid tenure of small and medium sized carnivorous theropod. That is longer than felids or canids have been around. More importantly that is longer than ratites have been around.

I really want to drive home the ratite comparison because dromaeosaurids are increasingly likely secondarily flightless - probably evolving from something like Microraptor that could glide if not fly in a limited capacity. So if we look at ratites it becomes apparent that they have done all sorts of weird things with their feathers once they became permanently grounded. Especially so with their flight feathers. Ostriches no longer have the stiffened vennaceous wing feathers of flighted birds but more open plumaceous ones. Cassowaries have quilled wings. These options are real possibilities for dromaeosaurids but should be analyzed and imbued within a likely evolutionary/ecological framework.

Cassowary. credit Gambier Bolton

I also gave Dakotaraptor a striking white feather patch on the front of its chest for bold display and intimidation. Such bold white patches - when contrasted against darker integument - are common in birds of prey and also some mammals such as various species of Asiatic bear.

Ursus thibetanus. credit Guerin Nicolas. CC3.0

I took this notion of feather disuse and even extreme reduction further in a rendering showcasing a Dromaeosaurus feeding scrum on a non-descript chasmosaurine ceratopsid. An azhdarchid and a troodon are looking on waiting for scraps.

feeding scrum by Duane Nash click on image for bigger shot

As you can see I really took the hyena analogy to the extreme even to the spotted scruffy coat. I reduced the wing feathering and eschewed tail feathers completely as this ground based, running, scavenging dromie had little need for them.



I also gave Dromaeosaurus a thick neck mane of coarse feathers for protection during skirmishes.

100 million years of terrestrial evolution from likely flighted ancestors allowed for substantial variation in appearance and function of dromaeosaurids; modern flightless birds show that flight feathers can become plumaceous or quilled; aggressively combative, usurping, and scavenging dromaeosaurids especially in hot and/or arid environs likely featured large areas of the head, neck, and chest bare or with feather reductions; such areas could have sported extreme skin adaptations that offered thermoregulatory, protective, social, and intimidatory benefits; for these dromaeosaurids new world vultures (cathartidae) and old world vultures (accipteridae) might offer more useful analogue behaviorally and physically than raptorial birds of prey (accipteridae); feathers could additionally have been arranged in coarse manes or thick tufts around the neck for protection as well as bold white/dark contrasting areas for intimidation.

One final note and this has to do with anthropomorphism - the ascription of human values, conceits, and emotions onto animals. One charge I have seen leveled at me is that I, to paraphrase, "depict many of my animals intentionally weird, ugly, or unattractive". To which I reply "duh, goal achieved".

I have always been transparent with my inspirations culturally on this blog - informed as I am by ugly music and ugly movies. I think it important that researchers be transparent with their inspirations, not just their scientific ones, to most reveal potential biases. We are all primarily cultural critters and it would be naive to think even the strictest and staunchest scientists are not first and foremost cultural creatures.

So when one looks at vultures gobbling and skirmishing over a carcass or the scruffy, uncouth appearance of hyenas and their cackles and the words "horrific", "disturbing", "ugly", and "revolting" are bandied about is this a cultural reaction or a more intrinsic, base natural one? Let us flip our way of thinking about combative scavengers... do we think about them with these conceits in our mind because of culture, or, because we ourselves are animals and most animals want to move away from the sight of such animals feeding? That is the that the shock, the visual awe, the intimidation we feel at the sight of these feeding events is the same gut level emotional response other animals feel: "I don't want to get near this cancerous looking, tumor faced, loud, shrill, dominating, repellent, and combative animal not because of some cultural tradition but because I too am an animal and I react on a visceral level to this display?"




Coming up a new hypothesis on dromaoesaurid biting technique because it really is all about the teeth...

Hey now... I really thought about splitting this post into two posts for both respective hypotheses, but for the sake of brevity and wrapping this series up I decided to combine them. Additionally, as I will elaborate on further, the two aspects I will focus in on here - biting & locomotion - are not mutually exclusive and one dovetails into the other. So I gave this article a really long title and hope you get something out of it!!

Readers of this series may have detected a slight yet pervasive diminution of the import of the famed "killing claw" over the course of these posts. In my first post I documented the shift in scientific thought on these claws from scythes that cut meter long slashes in prey to crampons that allowed hitching rides on the hides of dinosaurs to ultimately the prevalent modern interpretation of raptor prey restraint (RPR) model of Fowler et al. in which prey subequal in size is grasped by all four digits. I reiterated a point seldom mentioned from the Fowler et al. paper on the dromaeosaurid RPR hypothesis: relative to accipterids, the ungual grasping ability of dromaeosaurids was >not as strong< as these birds in that arena i.e. they were not simply scaled up hawks. Later in that post I suggested a role for the arm/wings for pummeling prey/combatants as the feet grasped and pinned the animal. In my next post focusing on aggressive/combative scavenging in these animals I focused in on digit II as a useful tool in pinning large carcasses down as the head, neck and teeth pulled back on flesh - an idea supported by the unique morphology of the denticles on these theropods and the presence of enlarged digit II claws in several birds that work in a similar fashion.

My contention is that the import of digit II - so highly regarded that it is referred to as the "killing claw" - has both culturally and scientifically influenced these animals to the point that other aspects have been enshrouded. But was the "killing claw" really the most pivotal aspect of these animals behavior and ecology? I think not, or at least >not always<.

If the use of the "killing claw" digit II was indeed the be all and end all of dromaeosaurid prey capture and feeding technique we should be able to make some predictions to test that assertion. That over the course of the 100 million year evolutionary trajectory of these animals an increasing reliance on ungual prey capture will 1) show a trend towards shorter and therefore stronger legs i.e. less cursorial adaptations 2) as firepower is concentrated in the feet for killing the robustness of the skull and teeth should hold steady or potentially diminish.  In the early Cretaceous Deinonychus we have a relatively sub-cursorial but highly adept foot grasper - again there is a bit of an inverse relationship between foot grasping strength and cursorial ability as I discussed in the first post and which Fowler et al. highlighted in their paper. I will cut and paste the source of this observation from the Fowler et al. paper:


As evidence for the purported trend in increasing foot strength Fowler et al. cite Deinonychus (early Cretaceous), and Velociraptor& Saurornitholestes (late Cretaceous). While Deinonychus and Velciraptor have relatively short metatarsi I can't see how they interpret the leggy Saurornitholestes as an example of this trend. Additionally there are some notable omissions, most obviously the name sake for the whole family Dromaeosaurus!!

In Dromaeosaurus albertensis cursorial adaptations are highlighted, the killing claw is relatively atrophied, and the skull is relatively massive and robust (almost tyrannosaurid like as GSP has commented). I mean just check out the skull of this animal, there is nothing slight, superficial, or atrophied about it at all:

robust head of Dromaeosaurus albertensis. credit LadyofHats. public domain

relatively diminished claw size/strength D. albertensis. credit LadyofHats. public domain

On the other hand digit II is not especially robust in Dromaeosaurus and the remaining unguals look more adapted towards a cursorial lifestyle than grasping. A "ground hawk" this was not.

Several of these trends towards diminished ungual strength and/or increasing skull robustness also play out in Dakotaraptor (cursorial w/diminished foot grasping ability) and the very robust skulled Atrociraptor.

Atrociraptor credit Ferahgo the assassin (Emily Willoughby) CC3.0

What am I getting at here? If anything the trend is towards increasing tooth and skull reliance over time >not always< towards increasing foot grasping & "killing claw" importance. I say >not always< because there were and likely always were dromaeosaurids that highlighted foot grasping ability. Sometimes foot grasping became diminished, sometimes it was very important. But what was always important and what was always highlighted in these animals was the jaws and teeth. They are the feature that always stayed pat or, if anything, increased in prominence.

No dromaeosaurids were not evolving protobeaks or going edentulous despite the persistent artistic meme and no they were not diminishing emphasis on teeth and jaws.

It really is all about the teeth....

To drive home this contention I want to revisit a famed piece of data that has caused quite a stir in terms of whom and how it was done - the famed Tenontosaurus bite marks and the case for Deinonychus"bite strength". A technical paper by Gignac et al. (2010), a blog post by Mark Witton, a blog post by central coast paleontologist, and an internet article/summary from The World of Animals all highlight the attention and thought these remains have attracted.

That these bite marks have evolved into a bit of a paleontological "who done it" has always irked me. Not because of a lack of data or some systemic problem with the analysis - but because of the pervasive "explaining away" of data that most parsimoniously points to Deinonychus as the perpetrator. Several  ideas have been bandied about in an attempt to account for these bite marks by Deinonychus, a predator that appears to not have an especially high bite force.

Let's unpack them:

1) An undescribed and undiscovered tyrannosauroid dinosaur did this damage.

We have seen this story before... tremendous damage to bone - no way a "blade toothed" theropod did it much less a puny dromie. Let's just imagine a stout toothed, bone crunching tyrannosauroid existed at a time when such animals were basically all blade toothed anyways, and make this essentially fictional animal the perpetrator. Made up tyrant lizards did it!! Pesky blade toothed theropods just stay in your lane - you guys can't bite through bone the way tyrant lizards can!!

As you can tell (snark alert) I am not so much a fan of this idea. We have evidence of Deinonychus being the most ubiquitous theropod in the area; the tooth arcade matches; broken teeth in the area; the well established Tentontosaurus - Deinonychus relationship - the whole tide of evidence points to Deinonychus. If a cryptic lineage of stout toothed, bony crunching tyrannosauroids existed at this time I will be happy to be proven wrong - as of now I know such evidence and of the tyrannosauroids from this time period they are blade toothed predators without expanded jaw musculature - although I have heard murmuring of tyrannosauroid teeth from the same formation (but blade toothed not lethal bananas).

2) Deinonychus could bite hard, but it did so extremely rarely.

I mean really? Remember when you kept hearing how humans only use 10% of their brain? Yeah, this explanation sounds a lot like that. Over designed with a bite force exceeding modern American alligators yet barely ever uses this strength? I can't really go with this thought.

3) Stronger bite than predicted from studies.

I don't think that this animal had much of a stronger bite than studies indicate. I believe that we have been a little bit more than led astray by always looking at static bite strength as opposed to other methods of cutting that highlight speed, friction, and getting those darn denticles to do the work for you. It really is all about the teeth and it really is all about getting the denticles to work in a way that maximizes cutting efficiency with minimal effort and wear & tear of the tooth.

Its high time we start looking at hypotheses that invoke Deinonychus as the prime perpetrator. I will  put out a hypothesis that highlights an unorthodox feeding mechanism in these animals, that is consistent with the data, and offers much explanatory power for the observed data.

To prime you for it I want to look at birds a bit (as usual). To really confound the situation the obvious choice is flamingoes - because what better to compare dromaeosaurids to than flamingoes, amirite?!?



I mean, excuse the poor video quality, but just look at those tongues go!! It is the tongue just pumping back and forth causing the whole neck to just vibrate. I have no idea why these flamingoes engage in this lingual vibration? Anyone ever see wild flamingoes do this? I would have to assume that they pump their tongues back and forth to filter food but in my observations of these captive Chilean flamingoes they just do it while walking around... probably just bored.

No I am not suggesting that Deinonychus had some sort of lingual vibrational apparatus set up - just pointing out how one muscular organ - the tongue - can move with such speed and power in this bird that it vibrates the whole head and neck of these animals. I mean can your tongue move with such speed and power that it causes the whole body to hummm and vibrate... ummm never mind. The message I am trying to convey here is that when we look at avian feeding mechanics - and by extension many dinosaurs and especially paravaians/maniraptorans/dromaeosaurids - there is a lot of potential for quick twitch muscle, full body and/or neck movement involved in the feding apparatus.  To drive home this point, literally, what would woodpeckers be without their exceptionally quick and rapid - fire neck movements? Yes, it is the skull of woodpeckers that is wonderfully equipped to handle the blows and stresses incurred but without the power and speed provided by the neck the woodpecker would, essentially, not peck. It would just be a bird with a strong skull.


An often overlooked aspect of feeding mechanics is elaborating on how parts of or the whole of the body is engaged in feeding mechanics - the head need not be looked at as an isolated aspect of the process. Regular readers should note that I have made this point before on antediluvian salad especially with regards to twist or torsional feeding (death rolls) in plesiosaurs and in my bonesaw shimmy hypothesis on Allosaurus in which it is rapid neck movement in both the fore and aft direction that allows the denticles on the front and back end of the tooth to saw right through tissue. Bite force was not especially important in that hypothesis, in fact tight clamping would work against free movement of the denticles over the tissue.

This hypothesis does take some inspiration from the bonesaw shimmy model but it does deviate from it in several ways.

I propose that fast twitch muscular contractions of the neck, torso, and even tail would pulse out vibrational waves of energy towards the head. As bipeds that do not have their front feet on the ground these pulses of vibrational energy would travel unhindered through the neck, head, teeth, and ultimately into the food item they are cutting into. As the vibrational energy literally vibrated the tooth back and forth into the food item the peculiar denticle pattern of dromaeosaurids comes into fruition as an optimized adaptation to literally bore and auger into tissue.


The most striking and unique feature about the denticles on Deinonychus is that they are fairly reduced on the front of the tooth but very pronounced on the rear. But even stranger is the manner in which they are curved on the rear side which is towards the tip of the tooth, referred to as apical hooking. Fowler et al. suggested that this unique denticle design would optimize cutting into tissue as the prey animal was held in the RPR model and the head of the dromaeosaurs was sub-vertical with the nose facing down and biting between the legs. However this suggestion by Fowler fails to address the issue that many other theropods likely held prey/food down with their feet and wrenched off bites in a sub-vertical manner yet these theropods did not evolve such weird denticles as seen in many dromaeosaurids.

But if we imagine each denticle as a "tooth" and each tooth having a respective duty in food processing a potentially new perspective emerges that could explain the unique bone damage ascribed to Deinonychus.


As the piece of food is grasped a strong bite is first established. The slight and reduced serrations on the front of the tooth are useful here in establishing a piercing bite - not very deep as their bite force was modest but merely a small indentation into the article of food. Once a purchase is made then the body commences vibrations - potentially a combination of head, neck, torso, and tail rapid fire twitches - which allow the tooth to bore and auger into the food particle i.e. bone. As the "bore hole" phase commences the utility of the weird apically hooked denticles comes into play as each denticle literally chips and shreds away at tissue like individual teeth. As the tooth works its way into the material it leaves a remarkably accurate impression of the tooth - a literal bore hole that for all intents and purpose can be read as a puncture. Once the integrity of the material is weakened substantially the item can be pinned with the arms and/or feet and the head and neck are pulled back strongly incurring further and more drastic damage as the tooth is dragged back through the (weakened) material literally leaving deep bone raking marks and furrows. It is also potentially possible that vibrations of the body were not emphasized or were in fact used in concert with multiple quick bites - essentially chattering of the jaw - in which micro - abrasions from the denticles work to carve into tissue.

This "vibrational feeding" hypothesis could potentially explain the two types of feeding traces recorded on the bones of Tentontosaurus which include longer gouges and simple punctures.



Above you see the type of "bone rakings" I mentioned earlier. An initial puncture is established and with the teeth embedded now the neck and body can pull back and rake through tissue.

What I suggest was occurring here is that these were investigative bites into bone. The theropods were gouging into the bones to see if there was ample nutritional value in them to justify the effort and potential wear of teeth. There would always be a three-way tradeoff between nutritional value versus the effort and wear on the animals feeding apparatus all of which is tempered by the relative health of the animal i.e. how desperate for food is it. Ultimately it looks like the theropods abandoned the bone consumption in this case.





That dromaeosaurid teeth occasionally show extreme wear - especially on the tips as should be predicted in this model - is very interesting.

worn tooth "Dromaoesauroides" wiki

Private "dromaeosaur" tooth Montana .84"

Judith River "dromaeosaur" tooth

Clearly these animals were putting some heavy wear on their chompers, especially when we account for the fact that they were not keeping their teeth for life. An interesting test would be to see if komodo dragon teeth ever show equal levels of wear. But again, not the best test because theropod teeth were actually superbly designed to withstand stress more than any other ziphodont predators (Brink, 2015) (including komodos), yet they were still showing drastic wear... these animals were not getting this type of wear from just eating small animals and delicately nipping carcasses I'll tell you that much.

Of course it is worth mentioning that there is a lot of room for deviation in this model and we need not assume that all dromies employed vibrational feeding to the same extent. Indeed Dromaeosaurus could have employed a lot more emphasis on traditional "power chomps" than what I suggested for Deinonychus.

In theropods, being both ziphodont toothed and bipedal, there is no go to analogy among modern tetrapods - birds don't quite tell the whole story and neither do monitor lizards. So maybe we should expect some unothodox feeding mechanics.

Lifestyles of not only the quick and cursorial but the slow and persistent as well...

And now for the tail. Probably the aspect >least likely< to be assumed to be involved in "making dromaeosaurids nasty again". But it is the tail that is the most important aspect of these animals I will argue. The tail is what really pulls together all the disparate attributes of these animals and makes them what they were. And what they were was quite literally the most successful in tenure small to medium sized terrestrial hunter - scavengers that have ever existed. A unique blend; of accipterid "raptor"; combative scavenging vulture; bone chomping hyena ; a dash of felid; and, yes, highly efficient cursors similar to kangaroos, hyenas, humans, wolverines, and Arctodus.

One of the persistent ideas that has gained popular recognition in recent years is that dromaeosaurids were sub-cursorial - that they were slow. A chief argument put forth to support this notion is that the ankle bones - the metarsii - were rather short. And this is true for many species - Deinonychus and Velociraptor in particular - that were gaining mechanical advantage of foot claw strength at the expense of speed. But this was not so true in several other species - Dakotaraptor and Dromaeosaurus for instance - that were leggy to an exceptional degree. I am just not at ease with suggestions that species at the lower end of the spectrum were heavy footed clunkers - they could probably all put on a decent burst of speed if need be. Ursids (da' bears) have all the hallmarks of real clunkers but put on good speed with their short ankles. Keep in mind that dromies were competing with larger - and in the case of tyrannosaurids likely larger and quicker - theropods as well as azhdarchids. It is not always about being the fastest - but about being more agile when fleeing a larger threat. With their arm - wings and long tails doubtless many dromies frustrated an angry tyrannosaurid back in the day with their superior agility.

The dromie tail, just like the dromie "killing claw" has gone through a twisted and convoluted history of interpretations and revisions. A brief recap. Ostrom interpreted the tail as an intricate balancing rod that facilitated use of the "killing claw" for kicking and hanging onto prey. Each subsequent interpretation of dromie killing technique from hanging onto the side of prey and biting to the RPR method invoked the tail as intricate balancing organ for their respective prime foraging technique.

To add further context to the strange saga of dromie tails I want to revisit a post from Pterosaur.net Blog  (remember that great site?) Dragon Tails: What Pterosaurs Teach Us About Velociraptor that made the strange and startling comparison between dromaeosaurid tails and rhamphorynchid tails... wtf? Well there is a comparison to be made there and it is not soooo strange when we work from the starting point that dromaeosaurids likely had flighted ancestors... so that they inherited a tail that - presumably - shared a convergence in form and function with rhamphorynchid pterosaurs.

credit Scott Hartman used w/permission . blog Scott Hartman's Skeletal Drawing

credit Scott Hartman used w/permission . blog Scott Hartman's Skeletal Drawing

So if dromaeosaurids inherited the weird morphology of their tails from flighted ancestors - full of chevrons, diminished musculature, partially ossified dual tendons (i.e. caudal rods) there becomes two rather interesting questions: 1) what adaptive benefit did these features incur in flighted dromaeosaurids and tailed pterosaurs? and 2) how was this morphology coopted into terrestrial based dromaeosaurids? Question number #1 I am going to leave alone but I think it is a long overdue question that needs analysis but question number #2 is what I am going to approach here.

credit Scott Persons

What I am going to suggest is that dromaeosaurids across all ranges of absolute speed and leg length - were highly efficient long distance pacers. They could and did just keep going for miles at a time at a relatively moderate pace. The whole lot of 'em could just run you to death. And the key to this long distance efficiency was the tail. The tail - the whole organ - served as an elastic recoil that allowed these animals to store, redistribute, and recoup energy for efficient, long distance traveling. I have seen scant attention to the tail as an aide in terrestrial efficiency in dromies. Despite the fact that these animals were terrestrial and the tail of dinosaurs is intimately linked with movement - especially per the caudemofemoralis muscle. Darren Naish raised the question of dromie tails back in 2008 (What the hell is going on with dromaeosaur tails?) in light of Norell & Makovicky (1999) describing an articulated and sinuous Velociraptor tail. The comment section is interesting. I do note in it a pervasive sentiment of trying to "explain away" the sinuous tail - the presupposition being that stiff tails is the better supported null in dromies to start with. But is a stiff tail the better supported null or is it just how we grew up expecting dromie tails to behave? In either case lateral flexibility shown in both Velociraptor and Bambiraptor seems to have prevailed. But there is one comment by Alan #19 that I believe was very prescient and which received literally no attention in the discussion.

I will be working from the assumption that dromaeosaurids - whatever abilities they had for arboreal behavior or even some amount of gliding or even "flight" in small ones - that they were basically terrestrial animals and that the tide of evolutionary impetus should create a better and more efficient terrestrially adapted animal. Not an evolutionary experiment, and not a maladapted kinda-climber, kinda-jumper, kinda-walker but a reasonably well equipped and efficient animal that could do all the things that we should expect a small to medium sized hunter - scavenger to do in a highly competitive ecosystem. In short they could climb, they could potentially even swoop, they could swim, but what they did the most was walk and run around. Namely that means that they could move fairly quickly and efficiently to highly localized food sources -   carcasses, hatching dinosaurs, large concentrations of prey. Especially given their long tenure, efficient terrestrial movement should almost be expected. Contra the "ground hawk" image we need not assume that these animals were >always< sit and wait ambushers or would swoop down from a perch. Indeed sit and wait ambushing is more of an ectothermic strategy and even when warm blooded predators do ambush from trees or from cover they choose spots that have a high degree of certainty that prey will be there fairly regularly. Dromies possibly could have utilized this tactic to some degree but I hardly think it was their dominant foraging strategy given that several species developed obvious cursorial adaptations and that some species lived in areas with little tree cover or sparse vegetation in general (i.e. dune fields).

From my own experimental paleontology in which I strapped on a huge tail to my butt at SVP Los Angeles and commenced to simultaneously entertain and annoy attendees I noted several patterns. What was really interesting to me is how much that darned tail moved around. Literally the smallest movement I made would thoroughly send the tail in motion. And what was most notable was the dramatic up and down oscillations that the tail went through as I walked. Each foot fall would create a simultaneous rise and fall of the tail - even the smallest and daintiest step. Don't believe me strap one on yourself and be a dinosaur for a day - you'll see what I am talking about.



These up and down movements of the tail that occurred simultaneously with each footfall likely occurred in all dinosaurs to some degree.  What is interesting is that dromaeosaurid tails - because of their "caudal rods" - were designed to diminish this up and down movement of the tail as thoroughly explained by Scott Persons on his post on dromie/rhamphorynchus tail convergence. Note in the pic below how the caudal rods are neatly stacked against one another on the vertical plane to limit movement dorso - ventrally.

Caudal rods in Deinonychus prevent up and down movement of tail credit Scott Persons

As has recently been illuminated by discoveries of articulated tails of Velociraptor and Bambiraptor these tails could still bend quite sinuously in the lateral realm.

Bambiraptor tail credit Scott Persons

So if the caudal rods of Deinonychus and other dromies diminish the up and down movement of the tails - which is a natural consequence of bipedal movement - we have some missing kinetic energy to account for. Energy is neither created nor destroyed. Something has happened to the energy otherwise absorbed and dissipated by the tail through up and down movement with each footfall in dromaeosaurids... where does it go? I suspect that this energy is recouped into the legs and aides in giving these animals just a little extra "bounce" to their step. The tail may work as a wonderful elastic rebound organ. We should potentially imagine dromies being very bouncy and springy as they paced along.

This model of locomotory efficiency is not without parallel in animals that have to move across vast expanses to find and locate rare and ephemeral food resources. A leading hypothesis concerning Arctodus is that it was a highly efficient long distance pacer that scavenged and usurped carcasses (Matheus, 2003) utilizing long legs and elastic recoil to travel at a moderate pace over long distances. Hyenas have long been noted for their efficient loping pace that allows large scale movements and carcass retrieval. Kangaroos and wallabies are well noted for their ability to travel long distance at an extremely energy efficient pace owing a lot to the elastic recoil in their leg tendons. Indeed a robotic kangaroo has been designed that utilizes such elastic recoil in the tail to recoup energy for movement.


I would be remiss not to mention the endurance running hypothesis has been invoked as a strategy for both scavenging and pursuit hunting in our own genus aided by the achilles tendon. To further quell the notion that short legs - such as in Deinonychus or Velociraptor - imply a suboptimal terrestrial movement capability let us not forget about wolverines which are notorious long range hunter -scavengers despite being very short limbed. I don't know if there have been any studies on the locomotory efficiency of these animals but I suspect there is something to 'em in those regards. There are at least loads of references to the marathon travels of these facultative scavengers.



"It is absolutely impossible for any human to keep up with a wolverine. What wolverine can do is just beyond human."

"A wolverine crosses a topo maps like we cross a street."

"They devour the landscape at a constant 4 mph regardless of terrain."

An energetic bundle of tooth, claw, and attitude? Switching from small game foraging to large carcass acquisition as the seasons dictate? Bone consumption? Able to outpace, outcompete, and outwork competitors that are several orders of magnitude larger in size? Thriving in areas and desolate habitats that other predators eschew (snowfields analogous to dune fields in these regards)? A little bit of the Gulo gulo in your dromie? You bet.

Making dromaeosaurids nasty again... Invoking the wolverine as a likely analogue for many dromies, it doesn't get much nastier than the demon of the north.

Ichnology: What Does It Tell Us?

Xing et. al. (2013) document a variety of dromaeosaurid trackways from the lower Cretaceouls Hekou group in China. The pace was not very high at about .75 meters/second which is about 1.7 mph or 2.7 km/hour. Average human walking speed is said to be about 3.1 mph or 5.0 km/hour. Let me just cut and paste the discussion:

So although these particular dromies seem to be moving along at slowish pace - perhaps they had full bellies or were just walking down for a drink. It is noteworthy that they mention several dromie ichno-species in the last paragraph that seem to be cruising along at quite brisk paces and one zipping along pretty good.

Dromaeosauripus from Korea at 4.86 m/s (Kim et al. 2008) which is 10.9 mph / 17.5 kmh

Paravipus  (Murdoch et al. 2010) at 1.67 m/s and 3.61 m/s which is 3.6 mph / 5.8 kmh and 8.1 mph / 13.0 kmh

Dromaeopodus at 1.63 m/s (Li et al. 2007; Kim et al. 2008) which is 3.6 mph / 5.8 kmh

Considering that to document an actual predatory chase in the footprint record is exceptionally rare and that there is no evidence that a chase was in progress in any of these instances the ichnological data is very interesting. We see a range of speeds here from the more leisurely .75 m/s to a quite hectic 4.86 m/s. If we assume that these are reasonable cruising speeds then the small sample size we have does point to a relatively fast paced "cruiser" similar to humans, wolverines, coyotes, and hyenas that can cover vaste expanses of land at an efficient pace as the penultimate terrestrial hunter - scavengers of their time.

The Seldom Mentioned Fact of Dromie Toe & Heel Pads

The trackways from this study demonstrate that dromies had big ol' foot pads like two toed ostriches but also large heel pads! So pay attention to this aspect paleo-artists  >at least some< dromies had big fat derpy looking foot/heel pads that are universally never depicted at all or large enough in paleo-art depictions (including my own). Why has this well documented aspect of dromaeosaur foot anatomy never penetrated into popular depictions? I mean no one - literally nobody - including world renowned paleoartists or more obscure/enthusiast artists depicts dromies with large heel pads. Yup the toes had big padding but the heel pad would have been very apparent in life. And this is from a peer reviewed paper with several notable authors including most notably to my western biased eyeballs, Phil Currie (who is btw the last author).




Such fleshy and large toe/heel pads would assist in stalking behavior by muffling sounds, stability, absorb stress from cursorial activity but I also have to wonder if such fleshy structures would diminish grasping effectiveness?



Also check out the base of digit II often reveals a bit of a fleshy toe pad. Dromaeosauripus yongjingensis represents a fairly large "Utahraptor" size dromie but other dromie footprints reveal fleshy toe pads and heel pads.




Kim et al. did a paper with reference to a speedy little dromie in the above discussion (Kim et al. 2008) from Korea of Dromaeosauripus moving along at about 4.86 meters per second (10.9 mph or 17.5 kmph).

Abstract:

The question is though does this represent a cruising speed or were we in fact lucky enough to document one of the rare instances that a theropod was actually "on the hunt"? Or neither? Could it be that dromies would normally walk at a fairly leisurely pace of less than 2 mph but when spurred into action (i.e. carcass or prey that have been detected via sensory cues but still require covering large terrain) that they then shift gears into a relatively higher pace 3 - 4 mph or even up to 8 - 10 mph / 16 -18 kmph? That is pretty fast but I hardly think it represent the top speed of these animals.

I also should give some space to the ichnological data pointing to at least six large dromies traveling in parallel and the special emphasis the authors give to the toe and heel pads in the footprints ( Li, 2007).






So when depicting the average large terrestrial dromie foot think more about ostrich feet than harpy eagle feet. Except that unlike ostriches dromies often had big ol' heel pads in addition to toe pads that would have further cushioned the foot and added a degree of stability normally not ascribed to these animals. The increased surface area would have facilitated greater efficacy and stability of movement in dubious terrain such as dune fields and mud flats.

ostrich foot credit Masteraah CC 2.0

Again it does beg the question that - at least among the dromies that sported such large heel & toe pads - how efficient a grip could have been enacted with the claws in the RPR model? I mean having such big, cushy organs between your claws and the animal you are gripping does pose some practical questions as goes the efficiency of such a grip.

A lot of questions to be answered but I do think that a fresh appraisal of these animals as primarily terrestrial long distance hunter - scavengers that have to cover a lot of ground efficiently is needed. Optimal walking versus optimal cruising speed can be addressed with larger sample size of ichnological data and computational methods... What I can say is that the anatomy of the tail likely has something to do with terrestrial locomotion and efficiency of gait is as good of a hypothesis to investigate as any...

These animals had to have been able to move and move well. They had to have traversed wide distances to secure meals in often times inhospitable terrain. They had to have competed against larger and aggressively hungry and growing youngsters of  tyrannosauroids, carcharodontosaurids, and other theropods. They had to get to carcasses before large pterosaurs got all the good stuff. They had to have been at least reasonably competent in these realms to have persisted as... I don't know... the longest tenured group of small - medium sized tetrapod terrestrial hunter - scavengers that ever existed ( I know I said it before but it bears repeating). Speedy thieves indeed.

Earlier in this article I suggested that there was a link between the tail and biting apparatus in these animals - that their functions dovetail together. At the risk of piling one hypothesis on top of another let me put it out there that the diminished dorso-ventral movement of the tail as dictated by the caudal rods would have shunted more of the potential energy towards the anterior of the body - essentially towards the head, jaws, and teeth - during vibrational feeding.

credit Duane Nash Tsaagan & Velociraptor

Final Thoughts

Both a scientific and cultural emphasis on the "killing claw" in dromaesaurids has obscured a more nuanced, multifaceted, and holistic approach to these animals; that the "ground hawk" model has so embedded itself into our conscious; that the potential role of arm-wings as brutal spiked clobbering devices analogous to wing pummeling in modern aves has been overlooked; that the teeth were highly specialized and brutal weapons in their own right capable of extreme insults to carcass integrity (including bones) and perhaps full body "vibrational feeding"; that the importance of head and tooth weaponry did not diminish over the evolutionary history of this group but sometimes increased while emphasis on "killing claw" and foot grasping capability did in fact sometimes diminish; that cursorial ability did often times increase in capability and that all dromaeosaurids may have benefited from elastic rebound provided by caudal rods in the tail enhancing long distance, mid-paced terrestrial efficiency of movement as well as large fleshy toe & heel pads; that life appearance may have been more varied than simply "grounded hawks" with "dapper" haircuts but imbued with much of the panoply of life appearance we see in ratites, predatory and scavenging accipterids, cathartidae, bucerotidae, galliformes, and other large/terrestrial aves including but not limited to large exposed fleshy areas including caruncles, wattles, frills, dewlaps, and other tough - elastic - and fleshy skin derived outgrowths for thermorgulation and sexo-social signaling; that these attributes when generously applied to an outstanding and long lasted dynasty - in fact the longest tenure of small to medium sized tetrapod terrestrial hunter - scavengers to have ever existed - create a strikingly original, efficient and for lack of a better term "nasty" eco-morphological package that punched above their own weights in many categories.

They were above all else... awesome... bro.

And finally... can we please stop calling them raptors? That name is already taken!! You may have noticed through the course of these articles that I have bounced a lot between dromaeosaurid and dromie... I probably in retrospect should have used the term eudromaeosaurid through out as they are what I am principally talking about here not microraptorines or unenlagines.

I vote for calling these guys "dromies"and am fully favor of eschewing the befuddled term "raptor".



Fowler, D. W., Freedman, E. A., Scannella, J. B., & Kambic, R. E. (2011). The predatory ecology of Deinonychus and the origin of flapping in birds. PLoS One, 6(12), e28964.

Gignac, P. M., Makovicky, P. J., Erickson, G. M., & Walsh, R. P. (2010). A description ofDeinonychus antirrhopus bite marks and estimates of bite force using tooth indentation simulations. Journal of Vertebrate Paleontology, 30(4), 1169-1177.

Kim, J.Y., Kim, K.S. and Lockley, M.G. 2008. New didactyl dinosaurs footprints (Dromaeosauripus hamanesnsi ichnogen. et ichnosp. nov.) from the Early Cretaceous Haman Formation, south coast of Korea. Palaeogeography, Paleoclimatology, Palaeoecology 262: 72-78


Li, Rihui., Lockley, M.G., Makovicky, P.J., Matsukawa, M., Norell, M.A., Harris. J.D., Liu, M., (2007) Behavioral and faunal implications of Early Cretaceous deinonychosaurian trackways from China. Naturwissenschaften (2008) 95: 185-191 online 
Xing, L., Li, D., Harris, J.D., Bell, P.R., Azuma, Y., Fujita, M., Lee, Y.−N., and Currie, P.J. 2013. A new deinonycho−

credit Coria & Currie. Murusraptor CC 4.0

Definitely shaping up to be the year of clan megaraptoridae with new species and information seeming to come down the pike on a weekly basis. When such a glut of data comes at us at such in such a breakneck pace and when - in the case of megaraptorans - such large questions remains such as "what the hell are they actually?"it does pay to sometimes take a breather and digest things a bit. By slowing down and picking things over details that might otherwise be glossed over might see the light of day. It is one such detail that I want to highlight in this post. It does take me into territory that I certainly don't specialize in nor have the inclination or background to really get into - cladistics.

Yup, in life you gotta know your strengths and weaknesses and, no disrespect to the hard work others put into this aspect of paleontology, it's simply not my bag folks. So no, don't expect any data matrix from me folks or some prolonged digression into some obscure processes or foramen. I like the "softer" aspects such as functional stuff, appearance, behavior, and ecology. That being said the one feature I want to highlight in this short post is a feature that bridges the adaptational approach which influences my thinking and the - no disrespect to practitioners - the bean counting of cladistics with its emphasis on character traits, data matrices, parsimony analysis... yawn I can almost feel myself getting sleepy just talking about it.

Megaraptorans have some pretty neat teeth to talk about, not so much for the features that they have, but for the features that they lack.

Megaraptoran teeth lack interdenticular sulci (White et al., 2015).

On lateral teeth:

"There are no interdenticular sulci between any of the denticles on the distal carina"

From the discussion:



As I keep saying (and feel free to say it along with me) : It really is all about the teeth.



Readers who have been following me for a while will no doubt recognize the importance of this dental feature in tracing my evolving line of thinking on the range of functional ability and carcass utilization in theropods that featured such adaptations. My first real exposure to this dental adaptation in theropods by a paper by Brink et al. (2015) Developmental and evolutionary novelty in the serrated teeth of theropods which I discussed in my post Death Comes Ripping: Bonesaw Theropods. Basically interdenticular sulci are recesses between the denticles that arise developmentally. They serve to alleviate stress and overall strengthen and prolong the life of the denticle and therefore cutting proficiency of the tooth over its lifespan and we see rough analogy in expansion slots built into bone saws and cutting blades. Such features are not found in sharks, monitors, and sabertooth cats therefore creating the argument that serrated theropod teeth are on a functional level superior to the the teeth of these animals in cutting longevity. Which makes perfect sense because it is theropods that had to carve up and butcher the largest, thickest skinned, bone plate armored, cartilaginous and tendinous food base the world has ever seen - their herbivorous brethren. Bone is just another tissue in this regard just as likely to be sawed through as armor plated skin or thick tendons and joints as enamel trumps all these tissues in hardness scale. It's not a mistake that a great many theropods had a head narrow side to side but thick and strong from top to bottom that bears some uncanny resemblance to a blade or hatchet. Bonesaw theropods are not likely right because they are "awesome-bro" but because from an adaptationist approach animals with such tough rinds were what they had to cut through on a day to day basis and we should expect their enamel covered (and therefore likely lip covered) teeth to do the task that was set out before them.

credit Brink et al. 2015 interdenticular sulci in theropods

An inference I am going to make is that megraptorans - as the most common large carnivore in their ecosystem in many places (but especially Australia) likely fed on titanosaurs (alive or dead it don't matter). Titanosaurs certainly had a tough rind and lots of evidence of osteoderms in that family.

From discussion White et al., 2015:


The logical question arises that if megaraptorans evolved from some putative tyrannosauroid or carcharodontosaurid why would they lose their interdenticular sulci with such a food base? The answer of course is that they would not lose such a feature that benefitted hypercarnivory and that they did not evolve from a hypercarnicorous carcharodontosaurid or tyrannosauroid. That still leaves open the potential of evolving from a tyrannosauroid that did not have interdenticular sulci and which was a small game scrounger - a possibilty White et al. allude to:


While evolving from a basal tyrannosauroid that lacked interdenticular sulci is still possible it might be more promising to look at even more basal common ancestors as a distinct possibility - a putative small game hunting coelurosaur. Something like Compsagnathus, Juravenator, or Scipionyx? Brink et al. (2015) suggested interdenticular sulci as a synapomorphy of theropods secondarily lost by troodontids and spinosaurids. However in their study they did not investigate basal coelurosaurs which might lack sulci due to their small prey diet. I don't know for certain if some coelurosaurs lack sulci? Anybody have any info on this question out there?

If some coelurosaurs lacked sulci a putative basal small prey coeulurosaur might just be the subject we are looking for. Such a culprit might produce the blending of features that have caused various analyses to suggest spinosaurid, carcharodontosaurid, and tyrannosauroid affinities. Such a culprit might make a good island hopper/rafter and colonizer (e.g. Japan/Australia) as several compsagnathid species do seem to have excelled at colonizing islands. Evolving from a small game hunter that lacked interdenticular sulci is consistent with the strange anomalous lack of interdenticular sulci in megraptorids given a likely "brontophagist" niche. Given enough time megaraptorids may have independently evolved interdenticual sulci but as they were possibly just recently patriated to brontophagy from (potentially) a small game hunting ancestor they only had simple serrations.

And if megaraptorids did indeed arise from a generalized, island hopping, small prey eating putative coelurosaur this sort of makes megaraptorids their own thang right? Not some obscure offshoot of carcharodontosaurids or tyrannosauroids but their own rightful clan of unique hypercarnivorous theropods. Not claiming this idea as unique to myself as I think several other bloggers/researchers have put forth the same idea of megaptorids being their own thing. But I think looking at the tooth adaptation adds another layer of evidence in favor of megaraptors being their own clan.

A final caveat is that just because megraptorids lacked interdenticula sulci does not suggest that they were inferior carcass renderers than theropods that had them. It merely means that their denticles did not last as long and something as simple as higher tooth replacement rates could have kept them equipped for efficient brontophagist shenanigans.

a very "coelurosaur looking" Megaraptor credit Tom Parker, 2015 CC 4.0

papers

Coria RA, Currie PJ (2016) A New Megaraptoran Dinosaur (Dinosauria, Theropoda, Megaraptoridae) from the Late Cretaceous of Patagonia. PLoS ONE 11(7): e0157973. doi:10.1371/journal.pone.0157973

Brink, K.S.  et. al. (2015)  Developmental and evolutionary novelty in the serrated teeth of theropod dinosaurs.
Scientific Reports 5, article no. 12338, July 2015


White, MA, Bell, PR, Cook, AG, Poropat, SF, Elliot, DA, (2015) The dentary of Australovenator wintonensis (Theropoda, Megaraptoridae); implications for megaraptorid dentition PeerJ Dec 2015 online