Friday, September 4, 2015

Terror Bird Update

I would be remiss if I didn't mention this study on the neck anatomy and implications for vigorous movement in the sagittal plane.

Tambussi CP, de Mendoza R, Degrange FJ, Picasso MB (2012) Flexibility along the Neck of the Neogene Terror Bird Andalgalornis steulleti (Aves Phorusrhacidae). PLoS ONE 7(5): e37701. doi:10.1371/journal.pone.0037701

Since both my scenario of bite, grind and pull and the hammer blow hypothesis both rely on extensive, dynamic, and robust neck musculature I can't really say that this work supports either notion more strongly.

What I did find of interest was the one comment someone left in the comment field for this PLoS ONE paper:

Well RobertoS, as you made the connection between Allosaurus/theropods way back on October 11, 2013 looks like you beat me to the punch a bit :^)  .... Just add the serrated tongue/choanal papillae and stress reducing headgear and it's complete!!

Furthermore the authors responded to this valid point and question with.... nothing!! Seriously what is with writers/researchers not fielding the questions that someone who took the time and energy to write on your very own published work - and probably had to go through the hastle of getting a PLoS ONE account. Say what you will about blogging but it is a living, breathing, responsive media.

Wednesday, September 2, 2015

Terror Birds Cometh: A New Theory Unlocking Phorusrhacid Feeding Dynamics & Ecology

*Warning scenes and depictions of extreme animal violence will commence

If you are new to this blog or this series of posts you will get best utility by starting with this post and working forwards to follow the thrust of my thought and ideas since these posts build into one another.

All right time to talk about terror birds or, as I like to think of them, the most recent radiation of large bodied terrestrial ziphodont theropods. Yep they have all the hallmarks of a true ziphodont theropod (except for, you know, the teeth); long and muscular neck; strong and rugose orbital brow ridge/top of skull; tall and deep skull braced for strength in the dorso-ventral plane but still relatively lightweight with a central hollow cavity and mechanically weak in the lateral plane; and a relatively weak bite force. Sound like anybody we know?

Now wait a second... what about that whole study pointing to these birds using a unique punch and jab routine in which repeated hammer blows delivered from the tip of the beak killed prey (Degrange et al. 2010)? Well, I am going to be getting into that study on Andalgalornis, in fact the data from that study is what I am going to use to prop up my contention that not only were teratornithids true big game hunting ziphodont predators they were "toothed" but not in the normal sense of the word. Like modern carcass rendering birds (new & old world vultures, petrels) they were equipped with cutlery in the form of a serrated tongue and choanal papillae that interfaced together to commence "choanal grinding" and were true flesh rendering machines of the highest caliber.

Andalgalornis credit Degrange et al. 2010

Again, note the congruence in general form to other theropods. Deep reinforced skull but with weight saving pneumatic cavities, narrow laterally, vaulted and thick orbital ridge and upper bill to absorb stress and strain. Remind you of somebody else with similar features?

Allosaurus credit Witmer labs
Now Allosaurus had those serrated, mechically reinforced teeth that, I argued, when combined with rapid dorsoventral movements of the neck in a "shimmy" motion instigated a diabolical bone saw technique to saw through skin, muscle, cartilage, and bone. The jaw was weak because the driving power was outsourced to the neck musculature. Phorusrachids lacked serrated teeth but they did have that strong downcurved beak. It was the hooked tip of the bill that grabbed onto a plug of meat from a prey animal (alive or dead) which brought said plug of meat into the shearing section - the middle of the jaw - I contend. Here a combination of rapid dorsoventral shimmies of the neck and rapid serrated tongue oscillations against the choanal papillae worked to render the meat. After being mechanically compromised, the flesh was broken off with a strong leveraging hook and pull action powered by the entire head, neck, and legs.

If choanal grinding was the predominant feeding method of these birds we should expect to see the highest capacity for stress and strain along the middle section of the jaw.

Granted these various finite element tests (from Degrange et al. 2010) on Andalgalornis, a golden eagle, and cariama were calculated with the bite force (133 N for the terror bird) centered at the tip of the jaw. It is worth looking at where the stress is greatest though. In order to help read this the small chart in the upper left of the diagram goes from relatively weak Von Mises force in the blue upwards to progressively higher forces through the green, blue, yellow, and red colors. If the color is white, well that means the force is off the charts and could potentially imply catastrophic mechanical failure with increasing force. In A, D & G we see that the lateral shake is not looking to good for any of the birds. Note that although the middle of the jaw for Andalgalornis is running red the tip of the beak is off the charts in white realm. I will return to lateral forces later in this post btw. If we look at B, E & H which is a normal bite the whole jaw line is in the nice blue realm for Andalgalornis while the tip of the beak is running red. This suggests that the tip of the beak - which supposedly is meant to withstand the most harrowing pressures when it is slammed into prey - is actually starting to trend into inferior performance during a normal bite pressure. What would happen if it slammed into struggling prey at even higher pressures? And finally we get to the pull back and here again we see the middle of the jaw outperforming the tip of the beak which we can quite readily see is going from red into white color implying the potential for catastrophic failure.

credit Marcos Cenizo
If the tip of the beak really functioned in the battle axe capacity that has been suggested for it as a way to stun/kill prey then we should expect this portion of the skull to show lots of blue color during these strain tests. Except we don't. In all the tests the middle of the jaw - which is where the action is occurring via choanal grinding I suggest - is outperforming the tip of the jaw.

Prediction is met and the battle axe interpretation appears less valid than typical choanal grinding as performed by modern carcass rendering birds (new & old world vultures/petrels) which I first discussed here.

*It should also not go unnoticed, per my previous post theorizing on the mechanical stress relief of theropod head crests/ridges/lacrimal crests that the surparorbital ridges maintain some of the most "blue" areas confirming the mechanical advantage I ascribed them.

Here are some other problems with the battle axe interpretation:

1) Lack of a modern analogue. If this method of prey acquisition is adaptive we should expect to see at least a few of the 10,000 or so birds in the world evolve some type of analogous prey capture technique. But they are lacking.

2) Difficulty striking a moving, struggling prey item with precision. To kill an animal with a precise blow to the back of the skull or neck as suggested in this method is likely more difficult than assumed. Felids have to grapple and restrain prey in order to initiate their precise biting mechanism. Repeated blows to kill larger prey items seems problematic too as such hooked tips tend to gouge into and get caught in flesh rather than cut through items.  We know this due to recent functional tests on the "sickle" claws of dromaeosaurid theropods working more as hooks than slicers. Additionally if a phorusrhacid gets entangled with a large prey item in this manner it is now in danger of sustaining destructive lateral forces from said prey struggling.

3) Dubious depth perception capabilities. For the head to swing back and then into a prey item it is hard to imagine how the phorusrhacid's eyes can stay trained on the prey - especially to hit precise targets such as the back of the skull, vertebral articulation ete etc. If I were to play creator for a second and wanted to design a bird that could pull off this killing technique I would make a sort of composite heron/woodpecker design. Exquisite depth perception, reinforced skull, straight and pointed bill for precise powerful blows. Phorusrhachid skull design is more similar to other carcass rendering birds and extinct theropods and most likely suggests that it fed in a similar fashion.

4) Prey size question. While the battle axe interpretation does not outright dismiss large prey capture it certainly favors a more small/medium game emphasis. This interpretation is ecologically untenable because - with the exception of a few land crocs and marsupial predators - phorusrhacids were far and away the largest, most diverse, and longest lasting predators in South America. They were also the only large South American predators that penetrated into North America. It just makes more ecological sense for them to prey on the largest prey items available to them. No extant terrestrial predators grow to the size of Titanis or Kelenken to primarily hunt prey the size of rabbits or small antelopes.

5) Bite strength. The authors of the Degrange et al. study openly struggle with the relatively weak bite force of Andalgalornis (133 N) which is less than several small mammalian predators. This relatively weak bite force, especially when combined with an increasingly akinetic skull is a bit of an enigma.

Larry Witmer (from here) on bite force:

"We were surprised that the force of biting wasn't greater in Andalgalornis. As we say in the article, our estimate of bite force might be a bit low for some technical reasons, but in general we don't think this bird was delivering hugely powerful bites."

6) Battle Axe/Hammer blow model not consistent with pneumatic structure within skull. Although the skull was large, reinforced mechanically in the dorso-vental plane, and, due to it's size, was absolutely heavy it was made relatively light by a large central pneumatic cavity in the upper jaw. In the battle axe model such a cavity would diminish the impact of blows because of loss of mass. Although, in fairness, such loss of mass could be compensated for by increased acceleration.

Andalgalornis with special prominence of choanal papillae & serrated tongue (c) Duane Nash

However these problems seem to melt away if we invoke a biting adaptation analogous to modern  carcass rendering birds (new & old world vultures, giant petrels) and Mesozoic theropods.

1) Loads of modern analogues for this method. In terror birds what you are essentially looking at is a hopped up lappet-faced vulture or giant petrel. While typically castigated as weak billed scavengers these birds routinely dominate the "predatory" eagles/hawks/falcons at carcasses, engage in combative behavior amongst themselves, drive off and intimidate mammalian carnivores, and are well established hunters and killers in their own right. The absolutely more massive and robust bodied/billed phorusrhachids would be even more impressive in these regards.

2) No precision bite necessary in this model. Prey is bit, hooked into by the bill tip, grinded in the mouth against serrated tongue and choanal papillae, and finally yanked back by the beak/neck & leg musculature until massive trauma facilitates death. Consumption of prey likely began before death. Not pretty or quick but a time honored theropod tradition.

3) Depth perception to a high degree is uncalled for. Through comparison with the way giant petrels and various vultures kill prey - through prolonged and repeated biting, yanking, and grinding encounters - we see it is not necessary for precision bites as called for in the battle axe model i.e. precise depth perception not necessary.

4) Average prey size increases. Giant petrels kill birds almost as large as themselves. Vultures kill relatively large ungulate calves, especially in mobs. Single phorusrhacids were likely capable of killing animals as large, or slightly larger, as themselves and, in groups, targeting animals absolutely larger than themselves. This makes sense ecologically because although South America hosted other large carnivores, phorusrhacids were the most diverse, widespread, long-lasting, and common large predators on the continent. It makes ecological sense for them to be targeting the largest prey available to them. There are no large 50 kg plus terrestrial predators that concentrate or is limited to a prey base that is 1/4 or less of their own size. You might not agree with this assertion but I can't think of one predator that is so ecologically hemmed in. Comments section is open. Peer review has been outsourced to the readers of this post. Generally large carnivores take prey up to and marginally beyond their own size.

5) Strong bite force is not necessary for this model. The cutting of meat via choanal grinding is dependent on speed and friction - not static pressure. The driving musculature facilitating prey trauma and flesh rendering is the serrated tongue and choanal papillae followed by pulls from the neck and  legs to pull off bites. These were the two largest muscle masses in the bird's body and are where we should look for possible clues to feeding tactics.

6) Large pneumatic cavity in skull convergent with large foramen (especially antorbital) in ziphodont theropod skulls. Such a weight saving adaptation proves useful in the need for rapid dorsoventral movements of entire head to assist in choanal grinding and pull back motions for prey dismemberment.

credit Degrange et al., pneumatic cavity in Andalgalornis skull

There is no need to invoke a feeding method for which there is no modern proxy, and which has significant mechanical and practical problems. A method largely congruent with modern day large carcass rendering birds (new & old world vultures, giant petrels) provides an elegant analogy for phorusrhacid feeding behavior albeit not taken to the extremes that phorusrhacids took such behavior and adaptations. All things being equal, it is more parsimonious to seek modern analogues - especially within the same order - than assume novel and unparalleled feeding adaptations.

For physical confirmation of the likely presence of potentially robust and mechanically reinfornced choanal papillae below is a still taken from the video from this study. You can clearly see the two large ridges of bone - on which the choanal papillae would have sat - in this shot of the roof of the mouth in Andalgalornis.

Turkey vulture mouth closeup showing serrated tongue & choanal papillae.
credit Williston Conservation Bird Trust Blog

Now the above gif is not provided to provide simple shock value, shocking as it is, but used to argue a corollary in the feeding apparatus that I argue is largely congruent among phorusrhacids, Mesozoic ziphodont theropods, and modern flesh rendering birds like giant petrels. You should note the strong leveraging capability of both the neck and legs working in conjunction. As well as the rapid "chewing motions" of the beak where I have argued the serrated and stiff tongue is shredding the tissue against the choanal papillae. But more importantly you want to note how the petrel works to keep the fight in the vertical realm. As mentioned earlier and as supported by the Degrange et al. study the phorusrhacid skull is weak when confronted with stresses in the lateral realm. Allosaurus and Mesozoic ziphodont theropods likewise had skulls that were ill-equipped to handle substantial stress in this realm. Petrels and vultures too have skulls likely weak in this realm and their feeding behavior supports this notion. They don't shake their head side to side when interacting with prey or a large carcass. Instead all these animals have a vested interest in keeping the field of battle strictly limited to the vertical plane.

Gina Carano Ground & Pound CC2.0
To make a rough analogy to sports let us look at the two main contrasting styles of fighting in mixed martial arts. You have fighters that are most comfortable and effective as upright strikers. They would rather play to their strengths and keep the fight off the mat but upright where their ability for rapid and powerful strikes is most useful. And then you have the specialist floor grapplers. They want to take the fight to the floor where they can utilize their superior grappling skills and specialized submission hold technique. And of course there are fighters that blend the two such as in the pic above where Gina Carano blends grappling with striking to devastating effect in a technique known as "ground and pound". The take home message is that it is in the fighters vested interest to dictate the terms of in what realm the fight occurs based on his/hers respective abilities.

So if we look at the topic from this perspective we can test it to see if it holds any merit based on presumed prey base for these birds. If phorusrhacids were analogous to "strikers" and wanted to keep the fight upright and in the vertical plane we should expect their prey base to be on the whole more like "grapplers" with a lower center of gravity and more geared towards taking the fight to the lateral realm. Which when we look at the presumed prey base of phorusrhacids they are, as a whole, not striking me as especially swift/cursorial track & field superstars.

Notoungulates (including toxodonts): although there are some smaller and swifter varieties like Protypotherium that might have been about as quick as rabbits they are overwhelmingly pretty stolid, clunky bruisers when you get down to it. Certainly no indication that they were on their way to matching the cursorial abilities of derived horses or antelopes. *Update, spoke too soon. Thomas Holtz caught my mistake - there were cursorial herbivores in South America. (see comments below)

Homalodotherium cunninghami. Notoungulate. credit Smokeybjb. CC3.0

Nesodon imbricatus. Charles R. Knight. public domain

Xenarthrans - these are the weird armored guys - including ground/tree sloths, armadillos, glyptodonts, anteaters & tamanduas. Again these animals are not going to win any races.

Megatherium americanum. Hakan Svensson. CC3.0
Glyptodon & Doedicurus. credit Robert Bruce Horsfall. public domain
And later after the great American interchange Gomphotheres were very successful in South America as well.

Stegomastondon mirificus. Wolfman SF. public domain
But don't forget about Macrauchenia. These interesting animals - what is that a camel spliced with an elephant - appear a little leggier than the other critters discussed so far. Speed is always a good tactic but, just giving it an eyeball test I would probably most likely infer it on par with a camel. Probably a good fast trot - but not on par with advanced horses/antelopes.

Macrauchenia patachonica. credit Robert Bruce Horsfall. public domain
But, whatever cursorial ability this animal had, what is more important is the suggestion that via its flexible shin and ankle bones these animals had outstanding agility. They could twist and turn on a dime. Admittedly I can't track down an actual source for this ability - it is just repeated several times on the wikipedia page. If anyone has more info, the comments section is open.

All right, so a prey base not necessarily highly cursorial but with armor plated skin, striking hand claws or clubbed tails, large size/robust build, and potentially good maneuverability. Does this sound familar? It should because these characteristics describe the Mesozoic prey base for theropods pretty much tit for tat.

Thyreophoran dinosaurs - stegosaurs, nodosaurs, and ankylosaurs - were both squat, armored, and to varying degrees armed with counterattacking tail clubs, shoulder spikes etc etc. Very reminiscent of xenarthan mammals such as armadillos/glyptodonts.

Pelorplites & H. sapiens immature female
Sauropods/Saurolophine hadrosaurs - Absolutely larger than theropods but also armed to varying degrees with strong tails/tail clubs, foot claws, dermal armor, and lateral sweeps of neck and tail. Analogous to gomphotheres but also tail wielding glyptodonts and giant sloths to a point.

Saurophaganax, Apatosaurus ajax, & Matt Weddel CC4.0

Therizinosaurs/Giant Oviraptors/Ornithomimids - Hand claws and stout build have often been compared to giant sloths.

Nothronychus credit Taylor/Weddel 2013 CC4.0

Cerartopsids/Pachycephalosaurians aka Marginocephalia - Stout, sturdy build & counterattacking head armament & beaks. Some parallels to notoungulates.

Montanoceratops cerorychos. credit Barnum Brown. public domain

Hadrosaurs/Iguanodonts - Turning agility superior to theropods perhaps analogous to turning ability in Macrauchenia vs. phorusrhacids. Kicks and tails swipes also important.

Iguanocolossus. credit lukas Panzarin from PLOS ONE

To have such high congruence in anti-predator strategies in Mesozoic dinosaurs and South American mammals should not be dismissed. I am not the first person to note this congruence. But it is suggestive of a similar method of attack - and weakness - shared between phorusrhacids and Mesozoic predatory theropods.

Faced with theropod marauders you can out-grow, out-fight, out-manoeuvre, or out armor them. Or some combination there of. But none of these methods was likely completely foolproof and phorusrhacids, as their theropod antecedents did likewise, probably were crafty enough to find flaws to exploit in all of the above defenses.

An interesting comparative test is useful when we compare placental mammalian predators/herbivores. The dominant trend here I would argue is that mammalian herbivores have been characterized by an increasing cursorial adaptation. This makes sense when we look at their predators. Canids and hyaenids are pursuit pack hunters. Felids are stealth grapplers. If you are big and strong it is sometimes a good tactic to stand your ground and fight - but this is only viable if you are many orders of magnitude larger and stronger than your predator. Otherwise running is probably the best tactic that works against both felids and canid type predators. Which is taken to extreme levels in various ungulates but especially horses and gazelles. If marsupial predators in South America were the prime danger to the large prey species that lived there we should expect them to evolve primarily in a direction that negated the likely stealth/ambush/grapple strategies employed by borhyaenids / sebecid crocodylomorphs / sabre-toothed Thylacosmilus. Except we don't see that pattern. South American prey species were relatively slow - although sometimes agile - and were more often big, clunky, armored brutes. Exactly opposite the pattern we see in mammalian pack hunting/ambush predator faunas but exactly congruent with Mesozoic ziphodont theropod dominated ecosystems. And like Mesozoic prey species they developed anti-predator armament - tail clubs, large clawed forelimbs, large size - useful in dealing a strong lateral blow to the theropod glass jaw.

The eastern Shasta ground sloth (Nothrotheriops texanus) and the four Titanis walleri terror birds had been at an impasse for several hours. Although both species were recent immigrants to North America the long standing predator prey arms race between these two lineages was not a recent development and heralded back tens of millions of years to their cooevolution on South America. The ground sloth had backed itself into a thicket of palmetto palms and cactus where it turned and faced its attackers.

Scrub Palmetto credit Jud McCranie CC4.0
The terror birds could not attack from the rear here and, faced with the pummeling hand claws of the sloth, were disadvantaged. But the location was in the full hot Florida sun and the birds then commenced a waiting game. When the sloth - after several hours in the sun and facing heat exhaustion - saw several of the scurrilous birds engage in an actual physical fight made it's break for cover. Less than 50 meters away it had excavated an extensive burrow system in the Karst topography. But the sloth would not make it 10 meters.

Although surprisingly quick, especially in dense brush, the sloth had failed to account for the location of the dominant matriarch of the birds. She, the largest of the flock, stood over 2.5 meters tall and weighed over 170 kg. Having quietly crept down to lie behind some palmettos posterior and adjacent to the sloth she had simply waited for her opportunity. When the sloth made for cover her long legs covered the distance in less than a second. Her aim was deliberate and intentional. She quickly drove into and bit with her hooked beak the softest and most exposed area on the rear of the sloth under the tail - it's anus . And with a series of almost imperceptibly quick serrated tongue and neck oscillations she had established a grip on the sloth's rectum and large intestine. Now with the muscles in her neck and muscular legs working in conjuction she pulled back hard. In a macabre and gruesome tug of war,  the sloth pulling in the other direction from the bird helped facilitate its own fatal outcome - disembowelment.

The sloth realizing it's predicament switched from fleeing to fighting. Mortally wounded it's fate was already sealed. Dancing and lunging from all directions the terror birds harried and harassed the cornered sloth. They knew that exhaustion and blood loss would hasten the death. And with their superior aerobic capacity, speed, and heat threshold the advantage lay firmly with the birds now.

Perhaps there was good reason for ground sloths to excavate and seek shelter in their extensive tunnel systems....

bats in ground sloth paleoburrow Brazil. c/o GeorgiaBeforePeople

We can just be thankful for the advent of relatively quick killing predators like felids and constricting/poisonous snakes. The most common method of killing prey during the Mesozoic and in Cenozoic South America was most likely breaching of the body cavity via the anal/cloacal opening. They eat your asshole out of you while you are still alive.

P.S. Some, or even most, might strongly disagree with my self-publishing style via blog post. Indeed the pitfalls of such method are well documented. I choose this method because it is accessible to all, and - with the use of visuals, video, links, gifs - a superior platform to express ideas in my opinion. Furthermore published academic papers tend to suck the life out of such work, are often behind paywalls, insist on inane formatting rules, cumbersome citation regulations, and peer review is no fool-proof method anyways. To be perfectly transparent I am not going to go through all that. So this is what you get. I know that I have an intelligent and growing audience so I would rather out-source the peer review process to them. If something can survive the slings and arrows of the internet comment section then maybe there is some merit there.

And what does everyone ask as soon as a new paper is published? "Is it online? open access? Can someone send me a pdf?"

Finally going through such prescribed channels is against my D.I.Y. ethos. Why should I PAY some other agency for the privilege to publish MY idea? Especially when they are going to insist on such a dry, cumbersome format? And then THEY get to profit from it?

And to those who simply will not cite, mention, or acknowledge my work because it has not gone through this prescribed process I give you this. If you claim to be a curious, scientifically minded person you should be less concerned with "THROUGH WHAT VENUE I AM GETTING THIS INFORMATION?" but instead "DOES THIS INFORMATION HAVE MERIT?" I have no hidden specimens outside of scientific scrutiny. Whatever I use is from online information available to all.

BTW I have seen popular books, personal communication, unpublished data, anecdotal records all in one form or another cited in reference in published peer reviewed material. So why not blog posts?



Degrange FJ, Tambussi CP, Moreno K, Witmer LM, Wroe S (2010) Mechanical Analysis of Feeding Behavior in the Extinct “Terror Bird” Andalgalornis steulleti (Gruiformes: Phorusrhacidae). PLoS ONE 5(8): e11856. doi:10.1371/journal.pone.0011856

Snively, Cotton, Ridgely & Witmer 2013 Multibody Dynamics Model of Head and Neck Function in Allosaurus (Dinosauria, Theropoda). Paleontologica Electronica May 2013

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Friday, August 28, 2015

Prehistoric Predators (Switek & Csotonyi) Is a Banal, Color-by-the-Numbers Cash Grab

Sorry, not going to mince any words here.

When a new paleo-art book aimed at younger audience comes down the pike I often check it out - especially when significant names are attached to it. I have in the past found books written for this age group more daring, audacious, visually inspiring, and willing to go out on a limb than the books written for a more adult or technically minded audience. And really, that's the way it should be. The young mind is generally more flexible and open to new interpretation than us olds. But such a book is not what I found in Prehistoric Predators. A book that, in my estimation, rests on its laurels relying on the name brand recognition of free lance science writer Brian Switek and paleo-artist Julius Csotonyi.

You might not like what I am going to say because it might strike you as a bit "personal" but too bad - this whole trend of "we always got to keep it nice and polite in the sciences" is something that really irks me. When the stakes are high, when personal and professional reputations are at risk, that is the fire that stokes the creative furnace of art, science, and literature and creates the highest level of work. We shouldn't give people a pass just because they achieved stuff in the past.

In the spirit of transparency I should be forthcoming regarding my opinions of these people.

I am admittedly biased against Csotonyi. I am no big fan of digital photogrammetry and to tell you the truth I wish it would just go away. If you don't have the time, patience, or effort to render plants, landscapes etc. etc, then maybe step aside for other artists that do. All in all digital photogrammetry is  the performance enhancing drug of paleoart, except, unlike in athletes, it doesn't even merit superior results. I feel digital photogrammetry lacks believability, composition, and soul. Yes, soul. When the artists physical hand meets medium an imitable transfer of their personal touch is made. Even computer aided illustration has this to a point. Digital photogrammetry is as dead as dead can be creatively, spiritually, and artistically in my opinion. That being said, Julius' capacity with this medium is generally better than most. But it his skill in actual drawing and painting that sets him apart. Even his quick gesture sketches are far superior to most painted imagery. I do own, and for the most part enjoy, his art book. And when he really sits down and paints the whole scene he is pretty much without equal and arguably deserved of the title of leading paleo-artist. But I have to knock off some points for being one of the biggest practitioners of always plopping your dinosaur (or other beastie) down on a vacant plain or simply conveniently framed on a bare patch of soil. This in my estimation is the biggest meme in paleoart and commits a real disservice in terms of portraying how animals actually interact with their environment in the real world. And he is overly conservative in his depictions - never taking a risk or going out on a limb. I am fully convinced that if he was a preeminent paleo-artist of the 80's & 90's that he would have been drawing scaly, featherless theropods.

And as for Brian Switek I am honestly a little biased against him too. Many would consider him an exceptional writer and, for a science writer, I will concede that he is above average in portraying accurate science communication. However I find his writing a little too "vanilla" for my personal liking. And, while my tastes are a little left of center, this could also be a function of his having to write to a larger, lay audience. But it certainly seems from his comments section that noted paleontologists and dedicated paleo-nuts frequent his blog posts. Speaking of his comments section it really irks me that he seems to never respond to questions, queries, or criticisms in his comments section often times directly asked of him - this just doesn't sit well with me. In having put yourself up as someone with some instructional capacity you should at least have the courtesy to respond to people who have taken the time to read your post and type a response. I mean the internet is really just one big competition for content viewing so why be so - how else can I interpret this non-action - condescending? There are a lot of people that would love to have the platform that he enjoys - nat geo contributor the seemingly go-to-guy for popular dino writing - I just don't get the feeling that he recognizes his privilege. And yeah, if you sense a little jealousy on my part you are very astute. I am an imperfect person in an imperfect world. But that does not negate these critiques. Cuz I'm just gonna put it all out there, in three years of my blogging here at antediluvian salad Brian (or Csotonyi) has never once commented upon, shared, or promoted, a single post of mine. There's that.

As I alluded to in the beginning of this post dinosaur - or other science based books - aimed towards children can be challenging, intellectually stimulating, and actually fairly deep. It's a myth that kids don't like to read - just look at the astonishing success of Harry Potter and other series - in fact an argument can be leveled that children are more dedicated and voracious readers than most adults. But you can't talk down to them or placate them as just children... which is exactly what this book does in the text. In fact the sheer triteness and lack of descriptive, exciting vocabulary in the text is really disappointing. It's rehashed and boring. Anyone armed with a few wikipedia pages and with no extensive knowledge of "prehistoric predators" could have wrote this book. The fictional vignettes are under-utilized and uninspired at best. When I was young lad I was reading The Dinosaur Heresies and Predatory Dinosaurs of the World. I might have been a little ahead of the curve but there is nothing in those books that is not explainable to kids - especially kids today with the internet at hand. There are a couple of throwaway lines that could have been taken further. For instance Switek mentions that no one knows what horns, bumps, and ridges on the tops of theropods head were for (don't worry I got that one). And he posits Masiakasaurus as a fish eater - when there is no real evidence for that, it's just always kind of been - what's the word - assumed. Long story short the text offers less information for a paleo-hungry kid than a wikipedia page (which they can all access anyways).

The choice of what animals get covered and what animals don't creates a weird hodge-podge effect. Why not take this more stimulating and still teachable angle to children: compare and contrast diaspid versus anapsid predatory technique over geologic time? That would have made for a more cogent and interesting book and potentially of use to children and lay adults. The book could have also contrasted the differing physiologies and respiratory systems of these two groups - especially with regards to monitor lizards/crocs showing signs of advanced respiratory tactics. Again kids could get this stuff if you don't overwhelm them with jargon and use interesting graphics and diagrams. If I was a kid I would feel this book is insulting my intelligence. Where are the monitor lizards, terrestrial crocs (or any crocs for that matter?), mosasaurs, plesiosaurs, ichthyosaurs, giant eagles, teratornithids? The only discernible pattern is that the animals chosen were critters that Csotonyi had images of lying around already for the most part. So yeah, I'm not a fan of the organization.

And now on to the art. With a few exceptions almost all of the Csotonyi art is lifted directly from his already published book, "The Paleoart of Julius Csotonyi", which again speaks to an obvious quick cash grab. Look - why should they presuppose that dedicated paleo-kids don't already own that volume? There is nothing in that admittedly awesome book that relegates it strictly to adults except for the arbitrary placement in the adult science section of Barnes & Nobles. If I was a kid I would feel ripped off - "I already freaking have all this imagery!!" However I am assuming that this book is aimed at dedicated paleo-kids. Perhaps it is not. The book is probably aimed at the more wider children's audience. You know the kids that are infatuated with dinosaurs for like a month but "grow out of it" - and then just want to play video games and shoot stuff? Yeah them. Because of this it will probably make a killing financially. But, at least in my mind, that doesn't excuse the less than stellar treatment of this young audience as a group hungry for exciting and revelatory new information in a way that they could digest. Instead the kids are given RAWR and big toothy things - which I am sure that they will enjoy - but I just think a big opportunity was missed here.

However there are a couple of new Csotonyi pieces that are worth mentioning... barely. What I remember - cuz I didn't buy a copy but read it in the store looking like some creepy big bearded dude in the children's section - is underwhelming. There was a rather insipid fight scene between an Ekrixinatosaurus and a Giganotosaurus. Kudos for picking a rather obscure abelisaurid but compositionally the piece is just kind of bleh... lacking any kind of atmosphere... Csotonyi is capable of just so much more. There was a very cliched "fight" scene between a T-rex and a Triceratops where they are just kind of staring at each other like junior high boys in their first real "fight". Boring. And then the kicker, the one piece where Csotonyi could have saved himself, a Spinosaurus rendering. But here again it looks rushed and just kind of typical. The spinosaurus has, what do you know, a giant saw-toothed fish Onchopristis in it's clutches - never seen that before. And it's standing upright like a good ol' well behaved bipedal theropod should - despite all the evidence to the contrary. Somehow presupposing an animal that we never had - a bipedal spinosaurus - is more parsimonious than the one we do have which is screaming out I'm not really any sort of a biped the way you imagine me to be?? Furthermore Csotonyi, in taking this overly cautious approach (which is actually the more radical one) takes complete liberty in depicting several Deltadromeus as hypercarnivorous theropods. Keep in mind that this is an animal that we have no head for and is most likely somewhat of a hipster ornithomimid - that is it was an ornithomimid before it was cool to be an ornithomimid. And the scene is plopped down in a gulf coast/Louisiana bayou style swamp full of giant swamp cypress trees. I have never heard any reference to giant swamp cypress type trees in the Kem Kem/ Cenomanian North Africa. But if Csotonyy did his homework he could have utilized the infinitely more interesting mangrove fern Weichselia reticulata as well as halophytic cheirolepidiacean conifers.  Long story short there is nothing in this rendering that you could have seen in a spinosaur rendering from 10 years ago - except the swayback sail.

As the title states of this post states I can only interpret this book as a quick crash grab. We should not be too surprised by this - after all these two gentlemen are hot off the heels of working - in a limited fashion albeit - on that movie. The thing is, I really don't have a problem with that. You got to put food on the table, make rent, I'm all for that actually. But let's call it what it is. The title of the book, the theme at hand, the obvious marketability to young readers - most likely boys - of big toothy critters that go RAWR - it's a quick buck. This book is not going to move the science forward, it's not going to challenge current dogma or pose new questions, and I don't consider it really acting as any kind of spark to young minds. It's a placeholder regarding current thought - which also implies there is going to be some dogma attached to it because dogma is part and parcel to any crop of leading paleontologists. And just because you put feathers on your theropods doesn't make you edgy at this point.

So if you have child in your life that might like dinosaurs a better pick would be A Field Guide to Dinosaurs (Gee & Rey). Or, before he went AWOL with digital what-ever-you-call-it, David Peters' A Gallery of Dinosaurs and Other Early Reptiles.

Yeah...... I SAID IT. Peters' book > Switek & Csotonyi's book.

P.S. My tone might be angry or overly aggressive but at the end of the day I feel these two have grown a little... complacent. They need a kick in the butt. There are many hungry artists and writers out there. A book full of deviantart renderings would have been way more compelling in my estimation. My ultimate goal is to get these two to step their game up - show a little more effort and respect for your audience, even if they are kids.

*update several hours later. Upon reflection and introspection this post is more about me and what I am going through right now than Switek or Csotonyi. I happen to have a lot of chemical imbalance going on in my brain right now, anger & bitterness, and uncertain future. This has helped me work through some of this. I am going to leave the post as it is because I believe in documenting what I get right and wrong here. And sometimes this blog is more than a documentation of my thoughts and ideas but also a kind of therapy and getting raw to the world. If Csotonyi or Switek read this know that you were simply caught in the crossfire of the war inside my head. I mean you no ill will. I actually greatly appreciate and acknowledge your contributions to the field of paleontology.

And the book is not that bad either, especially compared to other dino kids books out there. Other mitigating factors play into how the book comes out that are out of the control of both the author and artist. So, if you don't already have Csotonyi's book it is actually a worthwhile investment. And I concede I quite like some of the newer atmospheric pieces as well. Prehistoic Predators at Amazon.

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Sunday, August 23, 2015

Teratorn Blood Festival

Deep in the Peruvian Andes lives an astonishing tradition. In isolated villages throughout the area natives enact a symbolic clashing of civilizations. An Andean condor (Vultur gryphus), is captured, fed and groomed for several weeks, and finally latched onto the back of a bull in an arena.

credit Mollie Bloudoff. NPR
This visually startling tradition kicks off the annual Yawar, or blood festival. In the eyes of the native Peruvians the bird represents native Incan resistance, or even an Incan god, triumphant over the imperializing Spanish forces represented by the bull. Injury or death of the bird is seen as a portent of bad luck for the coming year.

credit Mollie Bloudoff. NPR
Now here is where a rather lengthy discussion pertaining to obvious issues of cruelty to animals and conservation ramifications for a dwindling population of these birds could be inserted. Countered in turn by charges of cultural relativism and the hypocrisy of western industrialized nations own dietary dependence on mechanized, polluting, CO2 enriching, factory farmed cruelty ridden meat crops.


Instead, for a more meta-analysis that should resonate with this audience, let the bull represent the merauding advances of synapsid mammalia and the condor represent the hallowed heritage of archosaurian theropod dominance.

lappet-faced vulture fends off mother Thompson gazelle while cohort
attacks fawn. credit Roy Mangersnes

The following, very tenable, paleo-fiction should best be enjoyed with the following Alice In Chains song "It Ain't Like That" cranked loud for maximum deathly ambience. Plus it has the line "vultures cry when flesh is ripping". And the singer died of a heroin overdose to lay rotting in his own house for several days before being discovered, there's that too.

Less than 15 minutes into its earthly existence the newborn Bison antiquus calf was already at deaths door. Despite its mother's valiant defenses the repeated bites, yanks, and shreddings of a dozen Terratornis merriami had at first yielded blood, then flesh, and finally breaching of the body cavity via trauma sustained to the anal region. Death was neither quick nor painless upon the calf but it was none the less assured.

Bison antiquus was the most common - and most aggressive - large herbivore of the La Brea plains and foothills. The young mother of this calf - it was her first calving - had in its life already faced down and survived encounters with dire wolves, smilodons, lions, and short faced bears. She was 2700 lbs of hoofed combative weaponry. But she had underestimated the predatory tactics of these birds.

While she had noticed the teratorns before - they always seem to be a dominating presence at any large carcass - in her finite thought processing machinery she had never considered these birds on par with the other four limbed terrestrial carnivores that she had dealt with. This was a grave mistake - because although the birds posed no threat to her - terratorns are responsible for more new born calf depredations among La Brean hoofed herbivores than all mammalian carnivores combined. The  other grave mistake of the mother was in choosing to give birth in the open sagebrush plains. Other, no doubt terratorn savvy, more experienced cows opted to calve in dense cottonwood/willow riparian thickets. In these closed quarters the big birds with their 12 foot (4 meter) wingspans could not manoeuvre.

And this flock of terratorns - the Bombardiers - anticipate at least some of the young bison making this mistake and every calving season gather in this same locale in anticipation of them. While other terratorns work in smaller flocks harassing deer, peccaries, and antelope for their newborns this flock has grown specialized - some might say even developing an incipient culture - in preying on bison calves. Some of the Bombardiers are over 50 years old and have been refining their hunting tactic for this long. The long life span and observant nature of these birds gives them an exquisite knowledge base concerning the habits of all the other fauna on the La Brean plains. They know when and where the mammalian predators move. How to follow turkey vultures that could locate a carcass in dense foliage with their sense of smell. When to move to the coast to feast on seabird colonies, marine mammal carcasses, and pinniped mortality events. When and where each herbivore species gives birth. Time and knowledge is on their side.

When the first terratorn struck it did not do so from the sky but it approached from the ground. And its object of intent was not the calf but the mother - nipping her on the tail just hard enough to send a shudder of pain through the mother's psyche. The cows next response at this unexpected intrusion was confusion, bewilderment, and ultimately anger. The bird had counted on this response. The mammalian brain was hardwired for emotion. The terratorns' brain was unencumbered with such emotional sentience. Instead the computational hardware of the bird brain had a much faster processing CPU. Information was gathered, processed, and acted on accordingly based on a constantly shifting positive/negative benefit scale. 

And so as the cow reacted to the increasing rage at the thought of this "mere bird" plucking at its tail it failed to notice the eleven other terratorns in the sky and on the ground who had been watching in anticipation for the mother to leave its calf unattended. And as she obliged their wishes by charging after the first terratorn - which mockingly sauntered off not by flying away but by nimbly running away - they fell upon the calf.

The birds went for the softest parts first - under the limbs, the neck, the anal region. No one bite was fatal. And the action was fast and almost imperceptible. While the large hooked jaw was the most obvious feature of the bird and the first to suggest how it killed the true damage occurred inside the bill. After the hook of the beak had seized a plug of tissue then the cutting technique commenced. Rapid fire movements of the stiff and serrated tongue would grind and pulverize the flesh against the minute rows of serrated papillae on the roof of the mouth. Augmented by rapid oscillation of the neck musculature the whole operation was incumbent not upon bite strength - which the bird lacked - but speed and friction - which the bird had in abundance.

Andean Condor still from youtube clip. Note the stiff/muscular yellow tongue that - when feeding - pumps back & forth shredding meat against the choanal papillae. 

In above gif note the large/stiff tongue starting to move back & forth in the male condor as it anticipates a feed. Another similar and independent observation of more rapid tongue movement in a griffon vulture with a hole in its neck from which its tongue lopped out was observed in Spain (Camina & Guerrero. 2013) and France. The morphology of the tongue - convergent in New & Old World vultures, and several tubenosed marine birds - notably giant petrels - is referred to as canaliculate. This style of tongue follows the contour of the lower jaw, with a canal or trough in the medial section, and serrated edges on both lateral edges.

By the time the mother bison realized that its newborn was being set upon by numerous teratorns she had been drawn away from her calf by over 60 feet (20 meters). Blood had already been spilled on the chapparal. Now confused, bewildered, and even more angry at these developments she rushed back in defense. However the teratorns, now emboldened by the taste of blood on their beaks,  redouble their efforts. They harry the cow from all angles. Several swoop from above at opposite angles, while others dart around on the ground like macabre turkeys plucking at her back legs and tails with their serrated tongues/papillae. And again they raise her ire to the point where she charges furiously at birds but in doing so leaving her calf open to repeated attacks.

The more experienced terratorns have several tactics that prove especially infuriating to the cow. One of these used during ground operations is to feign running away and when the cow draws near and prepares to gore the bird the bird deftly leaps off the ground and kicks its talons off the face and horns of the bison. And in doing so uses the momentum of the charging cow and their high wing loading to quickly become airborne.

The repeated strikes at the cow from ground and air and her fruitless charges have worked to fatigue her after 10 minutes. While her girth, power, and weight worked to her advantage against land bound mammalian carnivores they are proving a liability against the birds. They are always one step ahead of her. Meanwhile the body cavity of her calf has been breached and the birds are now essentially eating it alive. Her counterattacks have become increasingly half hearted and now the birds, sensing her loss of resolve, don't even bother to lift off when she charges and feed with impunity right in front of her. Smarting from the eventuality of the situation, her increasing fatigue, the blood on her own face, and the realization that she herself is now vulnerable to predator attack due to her fatigued state she concedes her calf to the birds.

And over the next several weeks the Bombardier flock continues to feed on bison calves - and even does battle successfully with a giant camel for its newborn. Several birds become so gloated that they can't fly and roost in some local oak trees until they digest their load of mammal flesh...

So that's my take on Teratornis merriami. It should come as no surprise to you that I don't really take seriously suggestions that it was some type of piscivore (really? terrestrial socal is not too much of a fishy place now or then - especially in tar pits where the great T. merriami is often pulled from). Or that it was some type of small prey land stalking specialist... eating rabbits (seriously sometimes paleontologists, in the pursuit of "conservative" interpretations actually jump the shark into less than tenable realms)? Nope this was a bird that was intimately tied to and dependent upon the large megafauna it co-evolved with and eventually became extinct with.

And while I am not the first to suggest such aggressive predatory tactics in teratornithids I am certainly the first to frame it in this fashion with an emphasis on calf predation/group tactics/choanal grinding.

Now I did this little bit of - extremely plausible - speculative paleofiction on T. merriami cuz, you know, I'm a California guy. You can make up what you will with what was going on with Argentavis magnificens...

L to R. T. merriami, CA Condor, Golden Eagle. credit Travis. CC2.0

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Tuesday, August 18, 2015

Convergence in Form and Function Across 230 Million Years of Theropod Evolution

Jack Horner can dispense with his mad scientist franken-chickenosaurus machinations. We already have plenty of fine and dandy carcass processing theropods in all corners of the world - land and sea - right now, thank you. In my last post, Allosaurus - More of a Vulture Than a Falcon, I described a remarkable convergence in several lineages of carcass rendering birds that use a macabre feeding technique I have dubbed "choanal grinding". This feeding method in turn inspired a theorized feeding technique in Allosaurus that I outlined and referred to as the "bonesaw shimmy" - the shimmy being a dance based upon rapid alternate movements of the shoulder, outlawed due to it's overtly sexual nature in the 1920's . This "bonesaw shimmy" in turn may yield implications for other theropods to varying degrees I suggested.

In this post I want to expose a known anatomical characteristic linking past and present carcass rendering theropods (forgive me for using the term theropod loosely as such, for me it implies both extant aves and Mesozoic theropods/paraves/true avialians unless otherwise specified) . This characteristic - which is so painfully obvious it has hid in plain sight - has the potential to offer much utility in inferring likely feeding behavior and technique in both Mesozoic and Cenozoic theropods.

But as I am one with a little bit of a penchant for theatrics, I do not want to introduce that overlooked anatomical characteristic just yet but instead let us first spend some time with the bearded vulture aka the Lammergeier (Gypaetus barbatus).

Lammergeir. credit unknown but too cool not to share
Is there really any bird more classically dinosaurian than the Lammergeir? Everybody coo coos about the cassowary but for my money, if you want a direct portal to theropodian antiquity look no further than the bearded vulture. Not only is it strikingly colored, eats bones/marrow with gusto, is pretty darn large but it is also - along with a suite of other "carrion birds" - more predatorial than generally appreciated. I have to encourage you to watch the following youtube clips. They really give you perspective on the size, intelligence, awareness, impact and general gravitas of these impressive birds. The trainer seems like a cool dude too but I have to subtract some points for use of the John Mayer music.

Impressive, no? And for some nice footage of bearded vultures at a feeding station. If you squint your eyes a bit, not too hard to imagine dromaeosaurids or unenlagines in the clip below.

If you are still smitten with the regal beauty of these birds here is a nice close up video (the first pic of this post is a screen grab from it).

Now maybe you have never spent that much time up close and personal with these birds until now. They are astonishing - and that strong dinosaurian vibe you get off their appearance is not a mistake. Whether or not you keyed into the anatomical congruence that unites 230 million years of carcass rendering theropods yet is ok - you probably subconsciously sense it.

What I am referring to - the uniting anatomical peculiarity - is the supraorbital ridge or brow ridge if you will present in this and many other carcass rendering birds and Mesozoic theropods. Relatively obscured in the lammergeier due to feathers it is more noticeable in the lappet-faced vulture below giving it that distinctive "evil" glare. Not coincidentally (as I will discuss) the lappet-faced vulture is a large vulture with a penchant for the particularly tough and gristly parts of carcasses as well as a noted predator.

lappet-faced vulture.ccsharealike2.0. credit KCZoofan
If we look at another unrelated large carcass rendering bird - my hometown hero, the Californian condor (Gymnogyps californianus) - we can see a relatively thick ridge along the top of the skull and thickening supraorbital ridge.

CA condor skull. credit Kai Schreiber. CCsharealike2.0
Additionally, in another lineage of carcass rendering birds - giant petrels - we see a strong rugose brow above the eye and flange anterior to the eye.

Southern Giant Petrel skull. credit OVAM. CCbylicense
note the "eagle eye" brow ridge. CC3.0 credit Graham Curran
Now this supraorbital ridge and thickening bone at the top of the skull I have noted in these birds - keep in mind these are all fairly disparate lineages of bird - shows convergence. Of course this "eagle eye" countenance is of course most noted in eagles. But if we look at their skulls something a little bit different is going on.

eagle skull. credit Kai Schreiber. CCsharealike2.0
Eagles have a distinctive flange or process of bone forming the ridge while in the above examples the ridge is more solidly built into the skull. As I discussed on my last post eagles and other raptorial birds of prey are inferior harvesters of large carcasses compared to vultures/petrels. Furthermore they are often shoved aside at feeding opportunities by "carrion birds". So for these reasons and because the more "raptorial" birds of prey kill with their talons and not their heads/beaks I am going to treat them as a bit of an outlier as goes the evolutionary narrative that you might already be guessing at.

The tops of Mesozoic theropod heads are also adorned with an array of crests, eye ridges, lacrimal horns, knobbly protuberances and often times fairly thick bone deposits. In fact you can take a fairly base model crest such as you see on Coelophysis or Allosaurus and the vast majority of predatory theropod heads are but slight deviations.

Coelophysis bauri

credit Witmer's Lab
Now these crests. ridges, rugosities, brow horns, bosses, and lacrimal horns that line the top of the skull  have to varying degrees been interpreted as display structures, built in sun visors, or head butting devices (again the bone in these structures is often very thick). However none of these ideas have been adequately tested nor has anyone suggested a reason why, for over 130 million years, theropods were so damn conservative in their choice of headgear?!? I mean that is a long time for any piece of apparel to stay in fashion. And if they were head butting devices, presumably used to avoid lethal biting, these animals sure didn't display much restraint in terms of face biting evinced by the numerous lines of evidence suggestive of such biting incidents.

Mapusasaurus roseae showing the thick lacrimal/nasal crests along top of skull. credit Kabachi CC2.0

Instead I am going to offer an alternative explanation: These structures - although potentially co-opted for display, combat, sun shielding - had their impetus not for any one of these reasons but were generated for biomechanical reasons.

The biomechanical origin for these structures lays in absorbing stresses and strains from strenuous feeding activities.

Again, let me get a little nuanced here because I think nuance is sometimes lacking in these types of discussions and people get hemmed into either/or debates. For sure, in critters like Dilophosaurus or Monolophosaurus these structures are custom built as display structures. But what I am suggesting is that if a structure is in fact a display structure - it is usually obvious. And in the vast majority of theropods the head gear is a lot more conservative and primarily serves a mechanical function.

If we look at the theropod head it is a compromise between strength and lightness of build. The head had to be strong enough to interact and sustain integrity through  vigorous encounters with prey/rivals. But it also had to be as light as possible to facilitate the rapid neck driven feeding mechanisms that were fairly ubiquitous across the group. The lacrimal horns, ridges, rugosities etc etc. serve as "energy dumps" where the stress and strains encountered across the mouth are transferred up and away and "dumped" into the thick deposits of bone and pneumatic cavities at the top of the skull. A study of stress and strain distribution in the skull of Allosaurus pretty much spells it all out.

Note how in the above visual (from Rayfield et al. looking at forces in the skull of Allosaurus) that compressive forces marked "yellow" are being concentrated towards the lacrimal, nasal, frontal bones up those struts of bone away from the tooth row. Most telling is the pic on the bottom right where the course of the compressive forces appears to be literally tracing the crest line on the top of the skull of the allosaurus. In fact if you take a second to look at the architecture of a theropod skull holistically - it appears biomechanically designed to move stress/strain away from the tooth row towards the top of the head. This makes sense for a predator that needs to bite stuff and does not want to suffer mechanical failure of its teeth/jaw. Excessive forces can be shunted away towards thick crests/nasal bosses/brow ridges etc etc. Not only that but it minimizes the deposition of heavy thick bone throughout the whole skull - which would add cumbersome weight - and maximizes the animal's ability to move its head quickly and efficiently.

credit Scott Robert AnselmoCC3.0. Trex

And you can see this thickening of the top of skull to full effect in the pic here of T-rex. A mechanical design begetting thick theropod crests. If we accept the maxim that form follows function the mechanical advantages of such a design elegantly explain the long tenure of the design.

Why has no one has approached the issue of why certain theropods have converged on such thick lacrimal/nasal/orbital ridges before is a good question. Maybe we just are taken in by the cool factor of it - they do add a bit of style and flair to their look. But, as I always tell my traffic school students, things have a way of hiding in plain sight.

Ok, so if my hypothesis has merit - that these structures serve as "dumps" for excessive forces incurred during vigorous feeding bouts - then a good test would be to see if said structures are diminished or absent in theropods that feed on small prey, fish, or have explored a more omnivorous or herbivorous lifestyle.

Ornitholestes hermanni. Osborn 1903. AMNH 619, holotype from Carpenter et al. 2005
Ornitholestes hermanni the famed "bird robber" of the Morrison. Yeah they have a nasal horn (update false no horn there)  - as I said earlier most likely such obvious features are display related - but if you look up on top things are pretty thin. And with it's reduced serrations, modest sized head, and gracile build this critter is assuredly a small game hunter. Prediction met.

Masiakasaurus knopfleri
Another theropod interpreted as a small game hunter Masiakasaurus knopfleri (more on this guy in a later post btw). While the top of the skull looks a little thickened there is but only the incipient hint of a crest and no big, thick supraorbital/lacrimal crest to speak of - at least not on the order of true ziphodont theropods. Prediction met.

Suchomimus.creditAStrangerin theAlps.CC2.0

Suchomimus tenerensis. Usually interpreted as a fish eater, although an opportunistic small/medium game predator is likely given the dino/pterosaur consumption shown in close relatives. And don't be fooled by the notion of "mere fish eater" either. Some of these fish on the menu were huge with heavy, ganoid scales. So in spinosaurs we see a single crest with some pretty thick looking bone as well as some nice ridges around the eyes. So although not as heavily crenulated/crested as carcharodontosaurids. allosaurids, tyrannosaurids and other large game hunting theropods there is still some amount of crest/ridge action consistent with the stresses likely incurred from a diet of small/medium game and large armored fish. Prediction met.

What is interesting is what we see in terms of headgear on several other medium-largish theropods that have also been suggested as occasional to frequent consumers of fishy - aquatic type prey. The species I am referring to are Dilophosaurus wetherelli - which Kirkland has been advocating as a fish eater for years - and Ceratosaurus nascicornis of which Bakker, more controversially, has been interpreting as a fish (esp. lungfish) predator for a while now.

credit Jaime A. Headden aka Qilong. CC3.0
Those frills are described as especially thin and fragile - a far cry from the gnarly thick crests of big game hunting ziphodont theropods. The lacrimal crest is relatively diminished. Given those relatively thin teeth, kinked snout, and generally gracile build a predominantly piscivorous - with potential inclusion of medium game/scavenging - adaptation is looking more and more promising. Prediction met.

Ceratosaurus. credit Tremaster. CC2.0
But Ceratosaurus clearly is relatively more robust in terms of headgear than Dilophosaurus, especially those lacrimal horns. So I am not ready to call it a dedicated piscivore - although it certainly could have opportunistically exploited lungfish, aquatic prey etc etc.

And what about dromaeosauridae? Well they run the gamut. But the pattern seems to hold up. Regardless of how big they are, dromaeosaurids with reduced serrations/adaptations for small game are  relatively impoverished in terms of strong head gear while dromaeosaurids with serrated teeth/deep skulls/homodont dentition aka "classic ziphodont" styled animals have relatively robust headgear. I am going to concentrate on two extremes.

One of my favorite dromaeosaurids is the South American unenlagine Austroraptor cabazi (Novas, 2008). The long low snout, conical dentition lacking serrations, and general build have inspired comparisons to spinosaurids - which became extinct at that point as far as we know in South America. So despite it's size Austroraptor appears to have been another small/medium game specialist with adaptations that speak to this. And if this is the case according to my theory it should fall short in terms of robust head gear comparatively speaking. Although it has a bit of rugosity on the top of the skull and some supraorbital/crest action it definitely falls short compared to true ziphodont theropods. Prediction met.

Austroraptor cabazi credit  Esv. CC3.0
And now as the contrast let's look at one of the smallest of all theropods Bambiraptor feinbergi *update potentially baby Sauronitholestes (Burnham et al., 2000). Despite it's cutie pie name and diminutive stature I am going to suggest Bambiraptor has a lot more in common morpho-ecologically with Allosaurus fragilis than it does with Sinornithoides youngi.

Bambiraptor feinbergi or baby Sauronitholestes?. credit Thesupermat. CC3.0

Dispense with your notions of what the size of the animal implies - this animal was punching above its weight. Check out the deep skull.  And those teeth, if you look at them closely they are not conical small game teeth but stout, serrated chompers. This little bastard must have been the bane of dinosaur nesting colonies. At this size (size matters) we might not expect the crest to be as sturdy as in larger ziphodont theropods but there is a nascent double crest arising along with a thickening lacrimal area anterior to the orbit - very analogous to the suggestion of a crest in the birds that I started this post with.

If we look at a ziphodont dromaeosaur that is a little bigger, such as Deinonychus, we should expect to see a relatively more sturdy development of head gear. Prediction met.

Deinonychus. credit onfirshwhois. CC3.0
Going further in our test if robust head gear was adaptive for ziphodont theropods then we should expect that theropods which made the transition to a more herbivorous/omnivorous adaptation should have diminished headgear.

Erlikosaurus andrewsii lacks a double or even single crest along the top of the jaw but it does have a bit of lacrimal bone thickening evident along the margin of the orbit. All in all though this animal does not have the same extent of thick crests/supraorbital ridges in ziphodont theropods. Prediction met.

I am not going to go into oviraptorids, avimids, or orhithomimids because their skulls have diverged substantially from the basic theropod design while therizinosaurids still maintain the same basic shape as other carnivorous theropods. But feel free to check out their skulls, they are lacking or diminished in robust headgear compared to ziphodont theropods.

But now I want to follow another line of inquiry this time into Cenozoic theropods .... errr birds .... errr what is the difference again? What I want to look at is extinct carcass rendering birds of the Cenozoic. If this hypothesis has merit we should see increasing robusticity at the top of these skulls in the form of solid crests, supraorbital ridges, lacrimal thickening, thick brows etc. etc. Luckily enough we have two great test groups - teratornids and phorusrhacids.

And what do you know, when we take even a cursory look at terror bird skulls the prediction is met.

Titanis walleri. credit Amanda. CC2.0
Andalgalornis CT scan. credit Witmer labs CC2.5
Note the thick ridge of bone (analogous to the crest in Mesozoic theropods) as well as the thick brow over the eye. These structures also served as "dumps" for excessive stress/strain imposed on the skull I am going to suggest.

A number of features pinpoint phorusrhacids as not only hearkening back to Mesozoic theropods in some sort of vague way, but I will argue that in form and function phorusrhacids are actually directly analogous to their Mesozoic brethren - especially Allosaurus. But that is for a future post. Let's just say for now that I doubt these were mere small game hunters...

And now on to the teratornids - a group that I am especially fond of because of their ubiquity at a location not too far from me, the La Brea tar pits.

To no one's shock the skull of Teratornis merriami has a strong ridge of bone right above the eye as showcased in the above picture from the La Brea Tar Pits Blog.

Teratornis merriami credit Ellen. CC2.0
The pic above lets the light catch the supraorbital ridge just right. These would have been astonishingly wicked looking birds. And, as I will argue in a future post, fishing or rabbit hunting was not their modus operandi.

Originally I wanted to include more detailed discussions on these two groups in this post but upon seeing how long this post already is I think it will be more practical to dedicate several future posts to both the terratornids and the phorusrhacids respectively. If you paid attention to my last post where I introduced a novel technique among modern flesh rendering birds it should not be too hard to guess what I will infer for both groups. Additionally, in doing so rectify some of the excessively conservative interpretations that have been dominating thought about how these birds fed.

To further embellish my point, that the reason for the bony protuberances, nasal/lacrimal crests and horns in theropods are not just there to make them look wicked but serve a biomechanical outlet for excessive stress, I want to point out that similar features are present in the skulls of other even more distantly related ziphodont predators.

Baurusuchus salgadoensis - the terrestrial croc of late Cretaceous Brazil was sporting some fashionable brow ridges.

credit Marco Aurelia Esparz CC3.0
Pristichampsus an early Cenozoic terrestrial ziphodont croc had the stunna' shades going for it as well.

credit Robert Bakker
How can I forget the wonderful Postosuchus and the assorted ziphodont rauisuchids/psuedosuchians ? This Triassic radiation of archosaurian predators had some impressive head gear too.

Postosuchus credit Mark Byzewski CC2.0
Batrachotomus kupferzellensis. credit Gedogeheo. CC3.0
Prestosuchus chiniquensis. credit Vince Smith. CC2.0
I can't forget to mention that monitors have some head crest/supraorbital ridging action occurring as well...

Perentie (Varanus giganteus) credit Flyingtoaster CC3.0
Although monitors, especially the Komodo dragon, tend to have relatively wider skulls than the relatively deeper and laterally compressed skulls of theropods so they are not the best comparison.

Is it just a coincidence that multiple lineages of Mesozoic theropods, terrestrial ziphodont crocodiles, pseudosuchians, several lineages of extinct/extant carnivorous birds, and monitor lizards all converged on similar headgear designs? I don't think so. This convergence is due to similar solutions to similar mechanical problems incumbent upon ziphodont skulls in both feeding and grappling with large prey items.

Majungasaurus crenatissimus. credit James St. John. CC2.0

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