Wednesday, May 20, 2015

What You See When You Google Image Search "Fighting Raptors"

Well let me be honest, I was trying to kill some time at work and decided to do a google image search for "fighting raptors" (I do work at a bird museum so it was a little defensible). Long story short I wanted to see if there are any dramatic images of sickle clawed theropods - or in the parlance of our time "raptors" - fighting in a manner reminiscent of how modern birds of prey (i.e. raptors before it was cool to be raptors) fight. As you can well imagine I got some interesting results and I will rate them in order of accuracy below.

A brief digression. For those of you who were well entrenched in dinosaur lore around the time the original Jurassic Park came out you should recall how that movie took a bastardized version of Velociraptor, beefed it up for scares (strangely prescient considering Utahraptor was discovered concurrently), and performed a marketing coup de grace and simply abbreviated Velociraptor to "raptor" for public consumption. Never mind the fact that "raptor" already served as a common name referring to birds of prey.

What has become increasingly clear is that in the intervening years since Jurassic Park the Mesozoic version of "raptor" has increasingly merged with the Cenozoic version of raptor in appearance, behavior, and ecology. The term "land hawk" is an apt description for sickle-clawed theropods as it encapsulates their feathered appearance, likely solitary tactic of prey wing mantling/grappling with foot claws, and likely penchant for small and medium sized prey and carrion. As has been well noted the film franchise has not kept pace with these discoveries... So you would think that "raptor" dinosaurs - as they are now construed - would make great paleoart fodder for dynamic intra or inter-species disputes just like modern fully avian raptors.

Sadly I was a little disappointed...

I want to break down the pics I saw into a couple of different genres so if you go do the google search yourself you will see most fall into these groups. So without further adieu let's get to the pics!!

And in order of accuracy....

1) MOST ACCURATE. Actual, you know, fighting raptors!!
credit Lyle Madison CDFW photo of the year

In this case a red-tailed hawk attempting to pilfer a freshly caught fish - called a "hitch" - from an osprey. You know I love fish eating theropods and kleptoparasitism and I would wager such behaviors went all the way back into the Triassic in theropods.

2) LESS ACCURATE. Disappointing Mesozoic "raptors". Ouch, painful to look at. A few ok deviantart pics but nothing that really blows you away.

3) SOMEWHAT LESS ACCURATE. Members of the Toronto basketball team called the Raptors getting into fights. Hey you can do a lot worse. They are aggressive, opportunistic, athletic, highly coordinated, and can jump or even fly depending on who you talk to.

But really there is not much fight in this team given their early departure from the playoffs this year so not really too many photos of the Toronto Raptors fighting (and even here it is a struggle for the ball not  a real fight worthy of the name "raptor").

4) OK A BIT OF A STRETCH BUT... the Lockheed Martin F-22 Raptor attacks from above, is weaponized, uses stealth, and has aerial maneuverability.



It's awful. No feathers. Pronated hands. Why are they not attacking each other? Better yet why are they not attacking that dumb synapsid offering up it's arms as chew toys? Why would such a disparate lineage even read human/primate/mammalian body language, eye contact, tone of voice, and facial expression with any kind of relative understanding?

There you have it Jurassic World raptors still less realistic than raptor jets, raptor basketball players, outdated raptor art, and raptor birds of prey.

Tuesday, May 19, 2015

Carcharodontosaurs Deadlifts Less Than World's Strongest Man!?!

Maybe my view is a little skewed but there does appear to be a general disdain for sports, team games, athletics, or just "jock" culture in general in many intellectual circles. Now I don't know if this stems from a general intellectual dismissiveness of such activities or you just were not picked for the kickball team in grade school but I think if one is interested in bio-mechanics - and paleo certainly counts here - then one would be remiss to, if not engage in physical activities, certainly take heed of sports/athletic endeavors for this simple fact: the human athlete is the most documented, studied, and chronicled organism from a bio-physical standpoint that we have.

Hell, even watching sports can teach you something about how muscles respond to stress, strain, and compensate to achieve a result. One of the more interesting trends I have been following is that when an athlete suffers an injury - and then continues to perform without letting the injury heal properly - the athlete will often suffer another injury. And, presumably, this stems from the body trying to compensate for the compromised portion of the body by putting strain on another part of the body in an often inefficient, and hence injury prone way. Now this highlights several things; heroics aside, you can do more harm to your injured body by not letting it heal; the body can recruit other muscle groups to help in movements during an injury; in most motions many muscle groups work together to achieve a movement.

Now going further with the concept of multiple muscles or even muscle groups collaborating to achieve a movement look at the impressive list of muscles used to achieve the deadlift.

According to the wiki page a proper deadlift engages 27 muscles from the legs, abdomen, back, and forearms. Even thought it is called a "lift" it is more of a pull and arm muscles only grip while the legs and core do the majority of the work. Now with these thoughts in mind regarding the diversity of muscles utilized in a bipedal hominid deadlift let us look at a recent paper looking at this question from the perspective of a gigantic bipedal theropods: the critical analysis of Robert Nicholls' "double death" scenario Balance and Strength - Estimating the Maximum Prey Lifting Potential of the Large Predatory Dinosaur Carcharodontosaurus saharicus. May 6 2015 The Anatomical Record.


Motivated by the work of palaeo-art “Double Death (2011),” a biomechanical analysis using three-dimensional digital models was conducted to assess the potential of a pair of the large, Late Cretaceous theropod dinosaur Carcharodontosaurus saharicus to successfully lift a medium-sized sauropod and not lose balance. Limaysaurus tessonei from the Late Cretaceous of South America was chosen as the sauropod as it is more completely known, but closely related to the rebbachisaurid sauropods found in the same deposits with C. saharicus. The body models incorporate the details of the low-density regions associated with lungs, systems of air sacs, and pneumatized axial skeletal regions. These details, along with the surface meshes of the models, were used to estimate the body masses and centers of mass of the two animals. It was found that a 6 t C. saharicus could successfully lift a mass of 2.5 t and not lose balance as the combined center of mass of the body and the load in the jaws would still be over the feet. However, the neck muscles were found to only be capable of producing enough force to hold up the head with an added mass of 424 kg held at the midpoint of the maxillary tooth row. The jaw adductor muscles were more powerful, and could have held a load of 512 kg. The more limiting neck constraint leads to the conclusion that two, adult C. saharicus could successfully lift a L. tessonei with a maximum body mass of 850 kg and a body length of 8.3 m. Anat Rec, 2015. © 2015 Wiley Periodicals, Inc.
According to this study although one individual C. saharicus could balance with an added weight at the front of 2.5 tons these animals were limited to lifting a weight of 425 kg singly or 850 kg doubly by a limited neck musculature. And just on the face of it this should raise some suspicions because the world record dead lift by a modern Homo sapien is more than what C. saharicus could do according to this study.

1155 lbs = 524 kg basically lifting 100 kg more than C. saharicus!?!

Wait a second this can't be write can it? Let us revisit the multitude of muscle groups that humans use in the deadlift - again arms are not that important - but the legs, abs, and arse sure are!! If you go back and read the abstract you will find no mention of the legs, abs, and arse compensating to help lift exceptional loads in C. saharicus. And when we are talking about the legs of theropods we are talking about the largest muscle group in them and any analysis of lifting would be remiss to discount them. Just like in humans where the arms/hands simply act as grips while the lower body does the lifting I would not be surprised if it was not much the same in theropods. To lift up something the whole body is lowered and the teeth, head, and neck simply get a good grip while it is the legs that do the heavy lifting. Lift with your legs they always say right!!

So yeah I think this paper attacks an interesting topic but I think it falls down a bit for me because it does not take into account the largest muscular group in theropods and does not account for multiple muscular groups working in concert.

How much could a large theropod like Caracharodontosaurus lift? I dunno but I think limitations based on balance such as those mentioned in the paper (2.5 tons individually for a 6 ton carch) are useful guidelines. I mean with increasing size muscle is going to be relatively less strong than at smaller sizes so I would not expect large theropods to hoist stuff up as big or larger than themselves like modern leopards do. 

credit Cindy Corcoran

If not lift completely off the ground I think it probable that large theropods could drag along fairly large carcasses on the ground like any good, self-respecting large predator today. Certainly activities like the one pictured below that inspired the paper in discussion by Robert Nicholls were par for the course and bodies of several thousand kilograms frequently tossed about like rag dolls by the largest theropods.

credit Robert Nicholls


Monday, May 4, 2015

Plesiosaur Machinations VIII: The Strange Case of Cope's Mosasaur Inside an Elasmosaur

Pilot Whale which presumably choked to death on large fish (Mahi mahi?). credit My Mataking - Eyes of the King
Animals sometimes do weird and inexplicable stuff. Even highly intelligent mammals like this short finned pilot whale (Globicepha macrorynchus) that tried to swallow too big a fish (Mahi mahi?). Now I have always felt that team synapsid gets short changed in terms of their dental arsenal not having the ability to constantly replace old/worn teeth like diapsids.  But, and more pertinent to the fate of this whale, team synapsid for whatever reasons is generally impoverished compared to diapsids in the ability to evolve a particularly stretchy throat to accommodate large food packages. With the exception of baleen whales I can not think of any mammals that have anything equivalent to a gular pouch that expands the opening to the esophagus for large food particles. Why is this? I don't know.

Now to be specific I am not talking about bowing of the bones in the mandible to accept large pieces of food but specifically the stretchy area of integument that covers the open "V" shaped area medial to each side of the mandible and extends into the "throat" and which allows animals with even fixed mandibles to eat particularly large chunks of food. Such as this large nile crocodile below struggling to swallow an infant hippo (although amazing we never see if the croc really gets the hippo down) ?!? On a slight tangent I wonder if the smaller crocs surrounding this big boomer and flencing off bites from the hippo are females he mates with and hence displays tolerance towards.

Now as you are watching the video pay special attention to the throat region of the large male and see the distended gular pouch effectively increasing the entrance to the throat. The gular pouch works the same way in monitor lizards, pelicans, and cormorants (and probably most carnivorous theropods). And pelicans swallow some damn big stuff too.

H. Krisp. wiki commons
So if you look at these skull pics of an immature nile crocodile to the left I want to draw your attention to the pic of the mandible on the bottom right. You will notice; the fused symphysis - also found in plesiosaurs; the conical, slightly recurved teeth - also found in most plesiosaurs; and notice the negative space on the interior of the mandible - this is where the expandable gular pouch lies which increases the size of the throat opening. And you should notice that in plesiosaurs a similar negative space - this "V" shaped area is also found.

Now traditionally the maximum parcel of food a plesiosaur is said to ingest corresponds to the diameter of the distance from each edge of the lower mandible. And if this dictum was followed for crocodiles it would produce a result of maximum food size ingested a lot smaller than what they actually accomplish. Same with monitor lizards, cormorants, and pelicans for that matter - even with flexible lower jaws. Now if plesiosaurs were synapsids, like the above unfortunate pilot whale, I would say that is a good proxy to determine maximum size of prey ingested. But being diapsids and being opportunistic carnivores lacking serrated teeth there is more than enough ecological and familial justification to infer a gular pouch in plesiosaurs. And this would substantially increase the maximum size of food ingested by plesiosaurs.

Styxosaurus credit Mike Everhart. used w/permission link
Beautifully displayed in this inferior and slightly oblique view of the skull of Styxosaurus (South Dakota School of Mines & technology link ) you can imagine that whole area on the underside of the mandible - the "V" shaped negative space - sporting a highly elastic gular pouch spreading wide to slide down fish, ammonites or whatever else it chooses to schlurp down. And if you think about the general shape of ammonites and a lot of fish actually in the side-to-side dimension they are relatively narrow but in the top-to-bottom dimension they are relatively longer. And with the jaws being hinged so far back plesiosaur could indeed open up wide - as the otherwise dated picture below by Charles R. Knight depicts.

Note the accurate degree of gate in the mouth Knight used for these Elasmosaurs
Now the prospects for what plesiosaurs may have put in their belly broadens quite a bit. And, as you probably know, there are plenty of accounts of stuff found in the belly of sauropterygians ranging from published to anecdotal. And one of the most amazing and seemingly improbable is Edward Drinker Cope's account of a mosasaur, reportedly Clidastes, preserved in situ inside an Elasmosaurus. Now, like most, I had discounted this report just out of hand. But it always pays to go look at the paper itself, and with the magic of the internet and the increasing trend of digitilization Cope's 1872 account from The Proceedings of the Academy of Natural Sciences of Philadelphia is online here.

Now, there are a number of marks against this; it was not collected by Cope but by Joseph Savage; it was scrappy and poorly preserved; and we don't have the mosasaur material anymore nor are we even sure it is Clidastes. And also Cope was the man, who just a few years earlier infamously got the head on the wrong end of Elasmosaurus to much embarrassment.

Edward Drinker Cope. 1869. Elasmosaurus incorrect end of tail depicted with head. 
But it is also worth mentioning that mosasaur inside the elasmosaur was published after the head on the tail debacle. Would Cope be so reckless with his professional reputation as to attach his name to another dubious elasmosaur account?

From Cope's account from Joseph Savage (the collector): "the vertebral column of the Clidastes was found immediately below that of the Plesiosauroid and in a reversed position as though it had been swallowed by the latter or larger reptile."

Now here I should interject that the identity of Clidastes is not equivocal and Mike Everhart (Oceans of Kansas) is suspect due to Clidastes being nearly extinct during the deposition of the Pierre Shale (so it could have been any mosasaur), Cope did not collect it, and the general scrappy and incomplete nature of the specimens.

"The largest vertebrate of the Clidastes were about three quarters the length and one forth the diameter of those of the Plesiosauroid, and the animal must have furnished a large, or at least long, mouthful for it's captor."

This is not as alarming as it sounds with regard to the length of the vertebrate. Plesiosuars have short, almost fish like vertebrate. Mosasaurs, not having long necks and with a shorter tenure in the ocean than plesiosaurs have relatively longer vertebrae. But these skeletal dimensions might offer a test of whether or not an elasmosaur, even with a distensible gular pouch, could have swallowed a mosasaur of those dimensions. And if you were to pick a mosasaur that might have been small enough to have been swallowed you can do a lot worse than Clidastes. They generally top off at about 3-4 meters and the size of recently published  Clidastes "pups" was about 2 feet/ .66 meters. It lacks the relatively deep chest of more advanced mosasaurs and is often described as harkening back to less derived aigailosaurs both in form and ecology. It was the most common mosasaur on the Gulf Coast, and with the exception of a find in Germany, did not penetrate very far north. It may have lacked the physiology for colder waters and lacked a blubber layer. It is very eel like.

Adult & neonate Clidastes. scale 1 meter. Field et al. 2015
Delving further into this strange - and unfortunately lost to science - fossil amalgamation I think it useful to play out some thought experiments on possible taphonomic scenarios that would have created this association. As I have mentioned several times in this series the torso of plesiosaurs was very rigidly constructed. The vertebral column, ribs, gastralia, pelvic and pectoral girdles formed a very solid and inflexible internal "shell". Drape thick muscles, tendons, and ligaments over the whole armament and you have a fairly strong framework - a structure that would be fairly hard to penetrate and also not too rapidly crumble apart after death. My point is trying to imagine how a small dead mosasaur would become enmeshed inside this torso taphonomically speaking becomes difficult to imagine. First the base of the neck had to become torn off, exposing the one large entrance near the front. Even here this becomes difficult to imagine - this area in plesiosaurs seems very robust with pectoral muscles and high vertebral processes supporting a heavy musculature. Anyways that neck opening has to be made and then - here it gets even more difficult to explain - the small carcass of the mosasaur has to make a miraculous entry into the torso either by drifting inside or being washed into it somehow headfirst through that small opening where the neck attaches to the torso. Remember that Savage specifically noted the orientation of the mosasaur (headfirst) and that it was underneath the elasmosaurs vertebral column. And also it should be mentioned that parts of the pectoral & pelvic girdles of the elasmosaur were present so it was not just the plesiosaurs spinal column rolling around isolated. Additionally cervical vertebrae were noted so that the neck was not completely out of the vicinity. And you should also note that turtle remains are also noted in the vicinity... stomach remains or taphonomic sorting?

For the mosasaur to get into the torso of the elasmosaur without being swallowed would require the elasmosaurs neck to be severed, the internal torso hollowed out, and the mosasaur to fortuitously drift headfirst through the neck opening (c) Mike Everhart used w/permission

At what point does it becomes more difficult to imagine how the mosasaur landed headfirst inside the torso of the elasmosaur than simply concluding it was actually swallowed? Also given the incomplete nature of preservation it is also possible that the mosasaur was partially dismembered prior to being swallowed.

Coming up for the next installment of Plesiosaur Machinations, I will look at the shark/ichthyosaur eating plesiosaurs of the Sundance Sea. I leave you with another pic of Styxosaurus highlighting the large area hypothetically filled by a gular pouch and enlarging the size of prey swallowed by plesiosaurs.

(c) Mike Everhart. used w.permission

Cheers!! and don't forget to like antediluvian salad on facebook!!

Friday, April 24, 2015

Plesiosaur Machinations Part VII: You Can't Handle the Thickness

credit Temura
credit Todd Marshall
credit Edward Drinker Cope
credit Doug Henderson

This post is on the tendency towards "shrink-wrapping" in plesiosaurs. As a quick explanation to those that are not familiar with the concept of shrink- wrapping in paleoart it is a noted tendency to highlight the skeletal framework of an extinct animal to the extent that the animal looks like skin draped over a framework of bone. As such it proves a bit of a disservice in communicating how real animals look with layers of fat, muscle, and integument largely obscuring the skeletal anatomy.

As I said earlier this artistic trope is quite noted with regards to terrestrial animals - especially theropods and sauropods - but here I want to argue the case that the depictions above shrink wrap plesiosaurs. But while they don't highlight the skeletal framework to the extent of much of what is classically regarded as "shrink wrapping" I will make the argument that the depictions above fall far short of the "girthiness" we should expect in such marine tetrapods.

(L) On the edge of life (R) prime of life credit NOAA Vancouver Aquarium

Now above are some interesting shots taken via drone that capture an astonishingly gaunt killer whale on left contrasted with a healthy whale on the right. I am quite impressed that they can even get that skinny and survive in cold waters off of British Columbia. Unfortunately this whale on the left - which is fully extending its pectoral fins for lift as it is getting relatively denser and denser in the water due to fat loss - soon expired after this photo was taken. It looks so strange to us because you can make out the skull shape, vertebral column - these are features usually obscured by fat on these animals. We have grown so accustomed to the plump, streamlined shape of marine mammals that even the slightest visible hint of a skeletal outline makes them look quite alien. But even in declining killer whales the smooth, streamlined shape is so important that they will take on extra water in their body as they lose fat simply to maintain the nice teardrop profile. In this manner it is sometimes hard to spot declining killer whales until the rather sudden and rapid onset of the famished stage to the left.

Now this fat layer - blubber - is very important in not just streamlining the animal, but helps it maintain high intermal temperatures, achieve proper buoyancy, serve as energy reserve, sustain growing internal neonates, and shield the vital organs from predatory attacks. If we take a more broad scale evolutionary perspective an argument can be leveled that in the acquisition of an increasingly pelagic adaptation in marine tetrapods - developing a blubber layer solves an awful lot of problems and is a pretty easy step to achieve.

Why wouldn't plesiosaurs - which lived at high latitudes, dove deep, gave birth to large live young, maintained high constant internal temperatures, depended on erratic food supplies, travelled widely, and (most importantly) represented the longest tenure of any marine tetrapod ever - develop a blubber layer is beyond me. It is an inference, but it is one of the most parsimonious inference one can make about plesiosaur soft anatomy in my opinion. Certainly more likely than the Jack Skeleton plesiosaur so often times depicted.

For these reasons - unless it was the intent of the illustrator to depict them as gaunt and on the edge of death - I can't really take the above illustrations seriously. The Marshall illustration in particular shows bony protuberances galore while the Henderson Elasmosaurus - and I hate to say it because I love me some Henderson art - suggests such a flimsy, gaunt, Nightmare Before Xmas styled animal that, in my opinion,  is outside the bounds of Darwinian evolution. As far as the other two illustrations go they do not necessarily show a bony countenance they just neglect any suggestion of blubber or musculature. Animals, especially active pelagic predators, just don't look like that.

Nope if you want to look towards an animal that serves as a good model for general plesiosaur appearance one can do a lot worse than looking at leatherback sea turtles, Dermochelys coriacea. These deep diving, temperate to subarctic ranging, endothermic, flipper propelled mega reptiles should be your go to animal for drawing and imagining plesiosaurs. And they are blubbery - with fat rolls all over the place. Just look at the guy below, it's like all of his double chins combined to form one mega chin!!

A blubbery reptile: Leatherback Sea Turtle (public domain)

So I would say look more towards Jabba the Hutt as opposed to Jack Skeleton when thinking about plesiosaur soft anatomy.

I really get a kick out of the above video. A Stellar sea lion - probably pilfering fish - got caught up in the netting of a large Siberian fishing vessel. Both a hominid and a canid are tossed around like rag dolls by the powerful pinniped after getting to close and not showing the proper respect. I guess they never got the memo that pinnipeds are in fact large, powerful carnivorans. Stellar sea lions, the largest of the sea lions,  are basically swimming grizzly bears. And constantly pushing, twisting, and rolling against a medium that has weight and resistance to it (i.e. water) is going to make actively swimming animals very strong all over their entire body in ways that terrestrial animals simply don't get. Tremendous trunk and vertebral muscles are what allow the pissed of Stellar to rag doll that fisherman.

UBC Stellar Sea Lion

Note strong attachments for muscles in the neck and especially those dorsal processes that allow such power and also the large muscle attachments on the scapula that anchored the main propulsive organs - the front flippers. If you look at plesiosaur skeletons you can see in most species - especially elasmosaurids - a similar trend of high dorsal processes anterior and superior to the forequarters is evident. This area - also coincident with the center of gravity - would have been the veritable seat of power in these animals from which they could change direction, death roll, and manoeuvre.

trunk of Morenosaurus. LACMNH. Duane Nash

If anything the dorsal processes are relatively larger in the above Late Cretaceous elasmosaur of California Morenosaurus than in the Stellar sea lion and are suggestive of relatively greater power along the entirety of the trunk and neck than the sea lion. Which brings me to the neck itself which is almost perpetually illustrated as a pea string, slender organ. I think this is a  mistake. Although musculature was heaviest at the base it continued along the whole of the neck to the head. A neck that may have weighed one ton or more, that stretched up to twenty feet, anchored by powereful musculature? The neck was not a weak point and so easily severed by megapredators as so often depicted. Towards the base it was like a tree trunk but even towards the head was probably about the thickness of a good sized anaconda.

Hydrotherosaurus c/o Adam Smith/
Now to this skeletal frame - and you should note that just the neck alone without added soft tissue is a lot thicker than typically depicted - you should add a generous layer of muscle, blubber, and skin. And the whole transition to head to tail should be seemless in profile. That is there are no gaps, protuberances, or other features that would diminish an efficient hydrodynamic profile. That means draw the transition to the back of the head to the neck with little to no definition. Remember the starving killer whale and why it is so strange to see an outline of the back of the skull in those guys.

Incorrect "Sunken Temples" Plesiosaurus. credit Dinotoyblog

As for the head itself don't give it sunken temples. Instead I refer you to pictures of male California Sea Lions - draw the head a bit like a  "knothead". "Knothead" is the less than affectionate term given to belligerent, large male CA sea lions by fishermen here - especially those that take up dock space or pilfer fish. The "knothead" term refers to the distinctive crest or bump on the top of the adult males' heads formed of muscle and fat. Plesiosaurs, especially elasmosaurids, seemed to increase the size and leverage of the temporal jaw closing muscles - which likely formed a visible hump or bump on the backside of these animals heads.

CA Sea Lion "knothead". credit Point Lobos Fndtn.

But maybe even more so than "knotheads" look at the heads of large constrictors, or maybe even more appropriate large conger eels (great video on fishing for congers with great death roll footage). Both sport impressive temporal bulges for jaw closing muscles that were probably likewise apparent in plesiosaurs.

Welles (1962) Callawayasaurus c/o Adam Smith. Plesiosauria
Conger Eel. credit Totally Awesome Fishing

And also for reference large boa snakes might offer some utility in plesiosaur heads:

Autopsy Boa Constrictor credit nadja & Sascha

Anaconda head. credit unknown. reptile forums

And with those animals in mind - sort of a mashup of conger eels, sea lions, and large constrictors - put all that over the hypothetical skull of Morenosaurus and have some nightmares.

Hypothetical skull Morenosaurus LACMNH. Duane Nash

So with robust heads, necks, and forequarters we now come to the torso which is essentially a sold base of bone and muscle. Seriously the robust skeletal framework of the torso with ribs, vertebrae, gastralia, pectoral and pelvic girdles is essentially like a "hard" internal shell serving as potentially protection for the vitals but a solid pectoral and pelvic girdle attachments for the muscles that powered the fore and hind flippers. And unlike sea lions, penguins, and sea turtles plesiosaurs were powered by two sets of flippers and thus doubly powerful in the torso. Long and short the torso was robust, powerful, and impressive. Artists should take note of the impressive forequarter regions of sea lions and leatherback sea turtles when depicting the fore and hindquarters of plesiosaurs but remaining cognizant of the distinctive possibility of a blubber layer further increasing the girth. Make 'em thick and don't apologize for it.

Oblique and ventral view of Thalassomedon. credit Adam Smith plesiosauria. Note pelvic & pectoral girdles

And finally, last but not least, is the tail. Now I know it has become in vogue to illustrate plesiosaurs with a little tail fin - and some likely had such a device especially the more pursuit/fast cruising varieties. But I doubt the utility of such a tail in most plesiosaurs. And when actually looking at the tails of some plesiosaurs, such as in the Morenosaurus I photographed below the tail looks downright "chunky". Now I keep hearing whiffs of plesiosaur remains showing flesh outlines of the body and the tail forming a seemless transition into a veritable "skink" like fleshy stump. And I like that idea, it could store fat and also act as a bit of predator lure. Here instead of my vulnerable distal neck and head bite onto my plump tail. It would be neat if some could shed their tails like many modern lizards, but that's a bit of a stretch. I wouldn't be surprised if the Mesozoic seas were not full of plesiosaurs with mangled/bitten/ slashed tails.

Tail Morenosaurus. LACMNH

Shingleback Skink Tiliqua rugosa. wiki

So there you have it: why you should give plesiosaurs "knotheads", thick necks, sea lion forequarters, sea turtle torsos, and shingleback tails. Give 'em the thickness.

Cheers!! Viva La RevoluciĆ³n plesiosaura!!

Monday, April 13, 2015

Plesiosaur Machinations VI: WE BITE!!

Plesiosaurs and the Misfits together at last!! I've done this occasionally in the past for this blog where a certain song fits and inspires the subject matter at hand. The song We Bite was one of the last songs recorded by the Glenn Danzig incarnation of The Misftis for the Earth A.D. period of the band and really captures the feral, almost proto thrash intensity of the band at the time. This was a shift from what can best be described as the more Ramones inspired, rockabilly punk rock the band had perfected prior to this unholy last gasp. Unlike many bands The Misfits got more intense, serious, and unhinged with age.

Carnivores Live For Pleasure - WE BITE!
Strike Out Like A Wolf's Endeavor - WE BITE!

Sea and Land J.W. Buel 1889

And I think a similar arms race was in effect with plesiosaur evolution culminating in the mighty elasmosaurids of the Cretaceous period. As I discussed in my last post I think plesiosaurs, and especially elasmosaurs, often times filled their tummies with ammonites wrenched from their shells through either rotational feeding, bashing them on the surface, or group feeding or some combination there of. I don't think it was a coincidence that the largest ammonites coincided with the largest elasmosaurids in the Cretaceous. 

Now some readers might be open to plesiosaurs/elasmosaurs preying on large, squishy cephalopods.... but why stop there?

A funny little social experiment played out in front of me on facebook the other day. A person I follow who has written a paleo inspired fictional novel posted the picture below on his feed.

Now if you are as much of a plesiosaur fanatic as myself you will see that not only is that T- rex skull too small for an adult skull but the purported "pliosaur skull" is actually a blown up Elasmosaurus skull. Yep you heard me right, it is the supposedly "gape limited, small fish only skull" of a long necked plesiosaur. What is interesting is that the picture got several hundred likes and comments on said thread and I had to be "that guy" that let people know that they were looking at a plesiosaur not a pliosaur. This tells me a couple of things - the distinction between the two groups is rather arbitrary and if they are so easily confused on general inspection maybe the line between the two was blurred ecologically as well... If one views pliosaurs as large game hunters with compromises in the skull that also allow exploitation of relatively small prey then maybe one could view long necked plesiosaurs as predators with a penchant for small prey but also the ability to exploit relatively large prey/carcassses on occasion. 

If you are keeping up to date on your pinniped behavioral ecology you probably are aware that for a while now a bit of a slow motion revolution has been occurring revealing that many pinniped species kill and consume prey of a size larger than generally presumed and quite frankly should make you a little leery with swimming with them. There was the recent documentation and publication noting grey seals as significant predators of harbor porpoises and seals. And just recently the publication: Intraguild predation and partial consumption of blue sharks Prionace glauca by Cape fur seals Arctocephalus pusillus pusillus (abstract).

Cape Fur Seal predating Blue Shark (photo Chris Fallows)
It was well known "Air Jaws" photographer Chris Fallows that witnessed the carnivoran on chondrichthyan carnage not one time but twice and on both occasions more than one shark was caught by the seal which ate only the energy rich viscera, especially the liver and stomach, disregarding the rest. From the Smithsonian article summarizing said study: " The behavior also suggests that traditional methods of diet estimation might be missing some key strands in the food web. Ecologists have long assumed that seals consume mainly small fish not exceeding about a foot long. But analyzing seal diets usually entails looking at what's found in their guts or in their feces, which in turn depends on recovering hard parts such as fish ear bones. If seals are selectively eating viscera from sharks - or any other large animal - that slippery evidence would have evaded scientists' detection methods, potentially leading to a biased picture of who's eating whom."

Now go back and read that last paragraph and replace the word seal with the word plesiosaur and you will see exactly what I am getting at. If plesiosaurs were leaving behind the hard parts of large prey (and it  should be tacitly obvious why they would do so due to possible choking) you will likely get a view of prey remains not too dissimilar to the small prey bias we see in plesiosaur stomach remains. And from a very small sample size of just a few preserved stomach remains that we have - which were biased from the start arguably - evolves the dogma that you will see repeated in just about every wikipedia page, every professional or popular article on plesiosaurs, every artistic depiction, and every animated feature: that "plesiosaurs (long necked) were a threat to nothing larger than a small squid or fish - specialists on exclusively small prey of the size that they could swallow whole in one bite and nothing larger." 

What do the nuts and bolts of plesiosaur skull anatomy suggest about plesiosaur (again when I say plesiosaur let us just assume I am talking about long necked varieties for simplicities sake) feeding ecology? Turns out that there is a rather extensive study of the jaw closing musculature and finite element analysis of the skull of the elasmosaur Libonectes morgani. An elasmosaurid from the Turonian stage of the early Late Cretaceous discovered in Texas, the preserved skull of Libonectes is generally considered the most complete elasmosaurid skull found to date. Almost as important is how creepy the picture of its excavation is below, almost as if it was dug out of a recent deposit representing some Lovecraftian beast brought to the light of day.

Libonectes morgani c/o T.W. Tidwell SMU College
Now what did the paper I talk about say? Well first of all the name of the paper is Plesiosaur Mastication: A biomechanical analysis of the skull and adductor chamber muscles in the Late Cretaceous Plesiosaur Albertonectes Paleontologica Electronica April 2013 (Araujo & Polcyn) and is online (link). The paper is pretty technical and I had to read it a couple of times to get the gist. There are several conclusions that the author come to best summarized in the exert from the abstract below:

Our results show that a larger physiological cross-section of the adductor muscles is achieved by an enlarged supratemporal fenestra which although it reduces mechanical performance of the skull, it is offset by increased strength of a taller parietal crest and temporal bar, given the loading is largely symmetrical, the lateral components are offsetting yielding a vertical force vector. This arrangement also increases the length of the adductor musculature and thus the total muscle mass. We propose that the reduced pterygoid flange indicates a diminished role for the pterygoideus muscle, reflecting a shift of the majority of the bite force to the adductor mandibulae externus, pseudotemporalis, and adductor mandibulae posterior muscles. Reduction of the pterygoideus falsifies the dual adductor system hypothesis, in which kinetic inertia and static pressure coexist.

Ok I do not disagree with anything they say there as far as anatomy and the results of their FEA. Probably the most important aspect of their paper is that Libonectes did not have a dual adductor system like crocodilians and that the pterygoideus muscle was diminished in importance compared to the muscles of the temporal region.  

So there was a shifting of importance away from pterygoideus muscles (i.e the big muscles at the rear of the lower jaw in crocodiles that make a big bulge) towards muscles of the temporal region (i.e. the notable forehead muscles of many predators). 

Araujo & Polcyn 2013.

As the temporal hole got larger in elasmosaurs this was associated with increased height of parietal crest and temporal bar that offset the mechanical compromise of the larger hole. This increased bite strength as well as mechanical performance. In other words the architecture of the whole temporal region grew not only to accommodate larger temporal muscles but to increase mechanical performance. And I do have to mention that Araujo et. al. did an exemplary job of running the stress & strain tests under the assorted variables at hand such as size of temporal hole, with or without various muscles etc etc that does convincingly show that these factors influence how the skull behaves mechanically.

At this point I should mention that I only give finite element analysis a little bit of leverage in terms of telling me what an animal can or can't do. The reason I don't put full faith in drawing strong conclusions from FEA is that the simulations treat the skull as if it is in a vacuum - always remember that a skull is attached to an animal. Muscles, tendons, skin, fat, bone, and ligaments can absorb and redistribute stress and strain throughout the body. FEA does not account for this. And when you have a long neck with 60 or 70 neck vertebrate that is a significant part of the body that can absorb and redistribute stresses incurred at the head. (BTW red means high stress and blue means low stress in the skull). What I do read from the FEA analysis here is that blue dominates, pressure is equally distributed across the biting portion with a strong vertical bite force. Nowhere in the paper do the authors address how much force Libonectes could bite with and this is unfortunate.

As mentioned earlier the paper discounts the dual adductor system of crocodilians due to the underdeveloped pterygoid attachments in Libonectes (and, by extension, other sauropterygians built the same way). Following form this they suggest an emphasis on speed rather than force in the jaw closing apparatus in these animals. As evidence they cite the fact that gharials also have diminished importance of the pterydoid muscles. As such the authors favor a prey choice of small teleost fish.

And here is where I disagree. There is a strong argument to be made that the importance of the pterygoid muscular apparatus in crocodilians has a lot to do with putting the bulk of the animal's anatomy under the water in order to conceal the head when approaching prey. Therefore in crocodilians  there is an adaptive constraint to shift the bulk of the jaw closing musculature underwater. Plesiosaurs were under no such constraint and, being obligate piscivores, gharials are under no such constraint as well. In fact the increase of the temporal hole and concurrent heightening of temporal and parietal bars speak to an increase in power and bite force. And if there was an abundance of slow twitch muscles in that ample temporal region we might be looking at a bite that could hold on for a long time...

So I don't really follow this line of logic to argue that Libonectes and plesiosaurs of a similar build were obligate piscivores. For me the strongest indicator of being an obligate piscivore is the shape of the jaw and teeth - and we see this pattern again and again in nature - long narrow jaws, with more or less homodont dentition. Dolphins do this, gharials do this, gar do this. Plesiosauromporph plesiosaurs fall outside of this pattern. In fact some genera of elasmosaurids such as Callawayasaurus, Terminonatator, and Zarafasaura developed increasingly shorter snouts with jagged heterodont dentition!!

Convergence in obligate piscivores. Dolphin, Gharial, and Gar. Credit Ariel Zambelich wired
As difficult as it is to imagine what plesiosauromorphs were it is also important to realize what they were not. To better illustrate this point I drew a hypothetical obligate piscivore plesiosauromorph as I imagine it should look based on what other obligate piscivores do.

This plesiosaur does not exist yet
I gave it a highly felxible mobile neck like an Anhinga, a longirostine jaw, binocular vision for accurate strikes, and rows of needle sharp dentition. A flexible and slim lower jaw that could flex open to assist in swallowing fish.

But it is hypothetical because no known long necked plesiosaur developed this suite of characteristics.

They could not fold their neck back like an Anhinga to dart after quick moving, small prey. Although there was stereoscopic vision in plesiosaurs most species show a tendency for the eyes to be directed upward which suggests capture and stalking from below. They did not evolve longirostine skulls to maximize their reach and speed at snapping up small, slippery prey. Although some species evolved needle like, slender dentition other species evolved jagged, well rooted 2" plus conical daggers that would not look out of place in the jaws of a nile crocodile. Long necked plesiosaurs did not loosen up the skulls of the lower jaws like their relatives snakes and lizards do as well as many fish eaters to help swallow fish. Instead the lower mandible became one solid bone basically sutured up completely and with a noted unification of the mandibular symphysis. I do think one lineage of plesiosaurs became obligate piscivores/small game only speicalists: the polycotlylids. Their jaws converge with other known fish specialists.

All in all the majority of plesiosauromorph plesiosaurs fail in many of the aspects that make obligate piscivores so successful. And I think we should be asking why is this?

The answer I believe is quite simply many of them were not the small prey specialists so often ascribed to them but opportunistic mesopredators able to subsist on a wide prey base. Again I make the analogy towards pinnipeds. Long purported to be exclusively piscivorous but now known to be capable predators of quite large tetrapod prey. And in order to push the envelope even a bit more I drew this depiction below of the Early Jurassic plesiosauromorph Occitanosaurus tournemiensis (usually sunk into Microcleidus) taking down the Early Jurassic pliosauromorph Hauffiosaurus. Both species were in the 3-4 meter range and as is pretty obvious Occitanosaurus was an elasmosaurid before it was cool to be an elasmosaurid and Hauffiosaurus was a polycotylid before it was cool to be a polycotylid. You should also take note of the fact that I am inverting the usual trope of "pliosauromorphs" handing "plesiosauromorphs" their asses.

Again, so much of this hinges on if you buy into a social adaptation for these animals - which is a very defensible argument as I went over before. And if you go down that rabbit hole it does in fact open up other rabbit holes to go down.

Now drowning is a time honored reptilian tradition. It does not have to be quick or easy but drowning  prey will get the job done. Once an animal is bitten and then latched onto - and Occitanosaurus did have the teeth to bite onto stuff - you have to wonder how the body, skull, and teeth will react to that

skull Occitanosaurus

forceful interaction. Again not as a single tooth, skull or muscle - but as an entire animal in which stresses and strains can be absorbed and redistributed throughout the entire body. I don't actually think that the jaws and teeth of pelsiosaurs have to be all that robust, strong, or tough at all to maintain a grip. Pythons and boas do just find latching onto and holding onto large, strong terrestrial prey. And python teeth and jaws are a lot more dainty than most plesiosaur teeth and jaws.

Python skull

In the ocean where animals are often a bit softer not operating at 1 g I see no compelling reason that the skull, teeth, and jaws could bite into and hold onto largish stuff. They had a wide gape, and some of those teeth were pretty impressive and temporal muscle size and strength seems to have increased over time as noted earlier. If the prey was too strong or large the plesiosaur would most likely lose a tooth and disengage before the skull itself suffered damage. Could it be possible that plesiosaurs had involuntary biofeedback processes that would disengage from the bite if it was too straining?

Again though, we have to imagine that if a long necked plesiosaur bit into a large and struggling prey item that as the prey item struggled those stresses would largely pass through the head of the plesiosaur into the long neck and ultimately the stout and strong torso of the animal. Remember that as the neck got closer to the body it got stiffer and heavier in these animals. The plesiosaur would simply roll along with the struggling prey and, especially if mob attacking said prey, simply outlast it.

Occitanosaurus tournemiensis. credit Hinweise link

In short I think the majority of typically long necked "plesiosaurian" plesiosaurs fit this dual functionality approach. Able to subsist on small and large food items this basically "mesopredator" niche faired well for them allowing them to outlast more specialized ichthyosaurs, sea crocodiles, leptocleidids, hypercarnivorous "pliosaurine" pliosaurs, and coexist with mosasaurs.

artist Charles Fuge c/o Love in the Time of Chasmosaurus

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