Wednesday, April 12, 2017

Sinking Ornithoscelidians: Sitting Ducks, Water Chevrotains & Ceratopsid Death Beds

River Bottom Running Ankylosaurus created for this blog piece by Robin Liesens

Dinosaurs back in the water and it feels sooo good… There are probably fewer narratives, memes, and dialogues as storied as the on and off again love affair between dinosaurs and the water in both scientific and popular forums. From pre-renaissance snorkeling duckbills and bottom walking brontosaurs to fanciful water world assertions that all dinosaurs were aquatic to bona-fide actual aquatic dinosaurs such as Spinosaurus the concept of dinosaurs in the water is one that is not soon to leave us. Dinosaurs sloshing, mucking, wallowing, foraging, and hiding in the water is an evocative suggestion because such depictions are not without analogue in many modern terrestrial tetrapods and large mammals in particular.

It is a contention of mine and this piece that just because an animal is not explicitly aquatic does not negate the potential for water to still shape and inform significant aspects of its biology and anatomy.

credit Burian

The opening depiction of a bottom running Ankylosaurus, kindly provided by Robin Liesens (Dontknowwhattodraw94), represents what I view as a logical culmination of the ornithischian body plan with relation to water. Ankylosaurus was quite possibly a sinker not a floater. An evolutionary arms race in ornithischians that gave this branch of dinosaurs especially thick, dense skin to protect from both theropods and intraspecific combat; an osteoderm studded skin; lack of skeletal pneumaticity; thick bones.  What this creates is the distinct possibility that ankylosaurids and perhaps other "dense" ornithischians - especially among thyreophorans and marginocephalians - did not actually float in the water as humans, birds, and most terrestrial mammals do but would sink right to the bottom like hippos, tapirs, and water chevrotains.

Bottom punting animals have a rich history here at antediluvian salad: bottom punting Spinosaurus is the ultimate conclusion I reached regarding the most likely aquatic propulsion for that animal. A necessary caveat of a good bottom punter that utilizes body density (as opposed to changing/shifting lung volume like aquatic turtles & crocodiles) is that actual swimming ability decreases as punting ability - and therefore body density - increases. This creates the paradoxical situation in hippos where they can not actually swim - hippos can not cross deep bodies of water because they sink like a stone. The same situation may have occurred in several ornithischians with thick dermis - not necessarily because they were semi-aquatic like hippos - but because they had embarked on a social and defensive strategy of thick skin, armor, and dense non-pneumatic skeletons. Body density and therefore punting ability and the inferred possible loss of actual swimming ability is an interesting side effect of their particular defensive anatomical pedigree.

All of this discussion should be couched in the recent elucidation (not withstanding a rebuttal) of a revelatory linkage of theropods and ornithischians into ornithoscelida (Baron, 2017). One of the most interesting questions that this linkage of neo-theropods and ornithischians raises is "why would ornithischians have lost the highly pneumatic (and presumably air sac filled) skeletons that most likely was ancestral to both ornithischians and theropods?"

Several commentators on the Tetrapod  Zoology post on ornithoscelidia approach this question and suggest that the ability to bottom feed on aquatic vegetations is a potential reason. I agree, but I would embellish this reasoning with a more dire and immediate consequence: ornithoscelidians did not want to be sitting ducks.

Sitting Duck: A person or thing with no protection against an attack or other source of danger.

Theropods we know were full of air - it is no stretch to imagine that, when immersed in water, they would have floated like a buoy. Maybe not sitting so high in the water as modern ducks but possibly with much of the head, neck, and even some of the back out of the water. This buoyancy would have made theropods excellent patrollers, explorers, and navigators of aquatic environments. It also may have helped in dispersal situations and survivorship of catastrophic aquatic inundations such as tsunamis and the relatively frequent storms surges, tidal inundations, and hurricanes that we should expect in hot house climates.

The floatability in water made diving a little bit difficult but not impossible: for theropods wanting to get under the water they simply point their nose in the direction that they want to go in and enact rear propulsion from the legs and tail. One of my favorite observation recorded of opportunistic hunter/scavenger theropods is of giant petrels (not known for diving abilities) repeated going underwater to scavenge a dead wedded seal.

creditJohn Van Den Hoff & Kim Newberry 2006

This digression also allows me to finally get rid of a piece of art I did quite a while back. Some opportunistic Coelophysis diving to scavenge a dicynodont at the bottom of some recent flood waters. Take note of the opportunistic pterodactyloids buzzing in for dislodged scraps.

Diving For Coins Coelophysis by Duane Nash

What is good for the goose is not necessarily good for the gander. While sitting high in the water may have been a benefit for wide ranging, opportunistic theropods sitting high up in the water for prey animals like ornithischians may have been fatal. And when we look at the earliest ornithischians they were not gigantic, heavily armed, or especially refined cursors. Their niche may have best been approximated by large rodents, small forest dwelling deer and antelope, and water chevrotains (Hyemosuchus aquaticus). It is water chevrotains I want to pay special attention to as here is a small herbivore that utilizes the water to good effect to literally vanish from predators. In the clip below the predator happens to be a modern predatory theropod , the crowned eagle. Also wonderfully narrated by Mr. Honey Badger himself:



Water chevrotains are noted for a thick, dense padding of skin along the rump and around the neck. Skin is actually the largest organ in the body and plays a little heralded but profound role in buoyancy as I discussed in bottom punting Spinosaurus. Readers should note that two other bottom punting specialists - tapirs and hippos - have thick skin and sink to the bottom.

It is quite possible that the earliest ornithischians quickly and resolutely diminished their system of air sacs and pneumatic condition - that in conjunction with thick and sometimes armored skin - allowed them to sit lower in the water. Analogous to water chevrotains and other small mammals that utilize the aquatic medium for concealment these earliest ornithischians set in motion a trend of aquatic concealment that - to greater or lesser degrees - likely persisted throughout their tenure with ornithopods like Thescelosaurus. There is no way to tell at this point where various ornithischians sat in the water - if they achieved true negative density like water chevrotains or if they just sat with more of their body submerged and that was good enough. But the point remains that such animals would have benefited cryptically by sitting lower in the water and dispensing with air sacs.

credit Duane Nash Thescelosaurus hiding underwater from topside threat
But if we assume that the baseline condition for ornithischians was to sit low in the water, when we add density in the form of scutes, osteoderms, thick skeletons, and heavy skulls then we have the likely potential for true bottom-punting, negative buoyancy situations to develop. Among both marginocephalians and thyreophornas we see many likely candidates that may have trended towards  negative buoyancy in these animals.

Water Sports by Duane Nash

For the most part I think bottom punting would have served these animals just fine. They still likely moved with grace and efficiency through bodies of water - they just did not swim in the strictest sense of the word. Moving through relatively shallow streams, rivers, ponds, sloughs, estuaries less than 5 meters deep or so not a problem and waters of this depth would have been what these animals came across in their day to day existence.  Indeed a ceratopsid could easily have been prone to flee into the water when chased by a theropod. The theropod in grave danger from a bottom punting ceratopsid as it floats vulnerable at the surface, its belly exposed to horn thrusts.

However in deeper waters that they could not get up to the surface in that they found themselves in trouble. I am specifically alluding to the ubiquity of ankylosaurid skeletons recovered from oceanic sediments - were these animals taken by sudden intrusions of sea water that put them in waters too deep to kick off the bottom to the surface in? And then you have the infamous ceratopsid mass bone beds, most notably from Centrosaurus that most likely document tremendous inundations of the ocean onto land. Researchers have struggled to explain why Centrosaurus - and pretty much nothing else but Centrosaurus - succumbed to these inundations. The wikipedia web page on the Hilda mega-bonebed summarizes a lot of the work on this topic.

The ubiquity of ceratopsids in these death assemblages is potentially explained by a negative buoyancy for these animals. All the theropods and hadrosaurs in the environment would float away. Ceratopsids were doomed in deep water.

Is there any independent evidence pointing us in the direction of thick skin in ceratopsids? By golly yes there is. Before the world fell in the love with the preternaturally adorable Psittacosaurus soft tissue restoration there was some other work on Psittacosaurus dermis (Lingham-Solia, 2008). What was revealed in the study is that the Psittacosaurus revealed a cross section cut out that had a remarkable density of 40 collagen layers and a skin thickness of .8 inches - which does not sound like a lot but is pretty astonishing for such a small animal. Unfortunately the author behind this work used these multiple layers of collagen to argue that not only was Psittacosaurus not "feathered" - which it wasn't of course - but that the feather impressions recorded on theropods are actually layers of collagen peeling off. The study was pirated by B.A.N.D.I.T. notions and what could have been a perfectly interesting document on exceptional skin thickness got turned into something that it shouldn't have. But let's not throw the baby out with the bath water here. The paper still shows a startling level of skin thickness - among the highest recorded in any vertebrate.



Again, let me hammer that point home, "multiple layers of collagenous fibres in excess of 25, among the highest recorded in vertebrates". There was an arms race in the Mesozoic, or more like it there was a skin race. Prey species attempted to evolve the thickest most durable hide they could to thwart those pesky theropods who more than kept pace in evolving forms more adept at sawing or crushing through thick and armored hides.

There has been some research into this topic of ceratopsid swimming and buoyancy (Henderson, 2014). The work concluded that ceratopsids sat in the water with their heads submerged. On the other hand hadrosaurids were much better natural swimmers with their head above water, hence the lack of hadrosaurids succumbing to such oceanic intrusions. This study points us in the right direction but it left out two things; 1) It did not account or even mention skin - a particularly dense skin may have sunk ceratopsids right to the bottom; 2) Pretty much any large tetrapod that lives in and around bodies of water has at least some capacity to move through bodies of water. Ceratopsids living on coastal Laramidia - especially bordering the western interior sea - would have have come across water all the time - lagoons, estuaries, swamps, tidal channels, rivers. It is absolutely non-sensical that an animal that comes across bodies of water daily has no way to efficiently move through them. Long time readers know that this is a constant theme I iterate on this blog: animals have to make sense. They have to reasonably move through their environment; eat; protect themselves; mate. When you conduct research that points you in the other direction - towards a maladaptive animal ill-equipped to deal with day to day encounters (such as bodies of water) - there is probably something wrong with your scenario. Such an animal, so maladapted to it's environment, would be selected for extinction and not leave a fossil record. Whenever you see a paleontologist utter the phrase "failed evolutionary experiments" run away quickly.

Now some have taken the mantra "most every tetrapod can swim" a little too literally:  I would add the caveat: "most every tetrapod can swim and/or bottom punt". Sinking ceratopsids right to the bottom would at least allow for movement through >most< bodies of water. For a large animal that can bottom punt it can still go through potentially fairly deep bodies of water, at least most bodies of water it will encounter on a daily basis. The problem is when it encounters bodies of water too deep to kick off of the bottom of to reach the surface. Large deep rivers, lakes, and extensions of the ocean can act as barriers to such animals. Or a catastrophic inundation of the ocean. That would be a big problem for negatively buoyant animals.

Bottom punting ceratopsids offers a potential explanation for why these animals were selectively killed while no other dinosaurs suffered comparable losses during large oceanic intrusions. It is not that ceratopsids could not move through water - they could quite well as a bottom punter - it is that in deep water they sank like a stone. It must have been horrific for them when the sea took over the land.

And this speculation is where it gets really cool. Because once you have a geographic barrier thwarting travel - in this case deep water - then you have a potential cause for speciation events. And we all know how wild with diversity ceratopsids on Laramidia got...



Papers

Baron MG, Norman DB, Barret PM (2017) A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature March 23, 2017

Henderson, D. 2014. Duck Soup: The floating fates of hadrosaurs and ceratopsians at Dinosaur Provincial Park, in Eberth, D. and Evans, D. (eds). Hadrosaurs. Bloomington: Indiana University Press. pp. 459-466

Lingham-Soliar, Theagarten. 2008. A unique cross-section through the skin of the dinosaur Psittacosaurus from China showing a complex fibre architecture. RSC Proceedings of Biological Sciences 2008 April 7. 275(1636) 775-780. online

Van Den Hoff, J & Newberry, K. 2006. Southern giant petrels diving on Macronectus giganteus diving on submerged carrion. Marine Ornithology 34: 61-64. online


"A Long habit of not thinking a thing wrong, gives it a superficial appearance of being right, and raises at first a formidable outcry in defense of custom". Thomas Paine


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Wednesday, April 5, 2017

Behind Your Bony Mask of Face

We all know what this post is about.

Below I will present a few small screen grabs cut out of larger pics of skulls. Let's just say that the representative animals are quite diverse phylogenetically. But despite the disparate vertebrae groups there are some striking similarities - and differences - in the bony texture. Before I reveal what animals are represented I would like readers to simply focus on the textures and patterns at hand, without any phylogenetic prejudices in mind.

One of these things is not like the other…

A.


B.



C.




D.



E.



F.



G.



H.



I. 



J.



K.





Again, without any phylogenetic prejudices creeping into your decision making, what similarities and differences do you observe? Which examples are more textured, which are less? There is a story to tell in all of this I will suggest and after the players are revealed I am going to offer that it is more behavioral - more adaptationist (there is that dirty word again) - than strictly phylogenetic.
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A. Belongs to a stinkin' fur ball, the lowland Paca. Amazing is it not? These zygmotatic plates have something to do with the sound propagation of this cheeky little guy. Not only is this animal a bit of an outlier for its mammalian pedigree but it is also an outlier for its terrestrial inclinations.

Lowland Paca. Cuniculus Paca credit Paolo W. Viscari Specimen of the Week
B. One of several fishes I will be highlighting. This is the fanged blenny - Meicanthus grammisteus - which injects an opioid peptide into its prey to sedate them. Incidentally I came across a link to this fish on Facebook on the same day as the Carr paper was dominating my fb news feeds. Credit Brian Fry.


C. Some gnarly looking catfish I "borrowed" off of Flickr. Thanks credit and © to Lonmelo.


D. Another fish, the North American bowfin. Coincidentally another predatory ambush predator of murky aquatic haunts… are you sensing a pattern yet?

North American Bowfin credit
E. American Crocodile. Exceptionally large and rugose skull.

American Crocodile. Credit Daderot Public Domain
F. Another aquatic tactile predator - Suchomimus tenerensis !! credit James St. John.


G. Another nippy creature of murky habits: Amphiuma tridactylum found on Tet Zoo originally from flickr site Boneman 81.


H. Ho hum, another swamp monster Metoposaurus credit Jeyradan, public domain.


I. Daspletosaurus horneri. Does it really compare that favorably to the other examples? I'm not seeing it. There is a general rugose nature to it, but hardly as intricate bone texture as the other examples…


J. The alligator snapping turtle. Seriously what is up with highly textured facial bone among stealth aquatic predators? Credit, pic allows zoom in functions.


K. Yet another textured skulled aquatic predator, the phytosaur Pseudopalatus mccauleyi. Petrified National Park credit Park Ranger. uploaded FunkMonk



Did I hit you over the head enough with rugose skulled swamp monsters?

The recent paper on the Two Medicine Formation tyrannosaur and associated facial integument inferences (Carr et al., 2017) makes the case that crocodile facial integument is the best inference for tyrannosaur facial integument. Also worth mentioning is that this is the argument that Tracy L. Ford (Ford, 2015) has long been making for quite some time (though Carr et al. did not deem fit to mention him). While the media has certainly ran with the story, at least in the online paleo community reaction to this inference has been highly skeptical. I don't want to recount the variable criticisms to Carr et al's inferences as many have done that already. However what  should not be lost on our observations is that several of these textured skulls above come from animals that do not have tightly adhering skin texture such as the various amphibians. Or even have scales at all.

There is potentially a story to tell here...

Let me make another analogy to fantasy creatures. For me one of the most entertaining aspects of fantasy creature creation is to unpack the various - and often times disparate - elements from contemporary or extinct creatures that are spliced together to create a fictional animal. For me one of the most successful creature splices of recent years is the Bashee and Great leonopteryx from Avatar. Darren Naish does an excellent unpacking of the various inspirations and spliced bits of microraptor, bird, pterosaur, bat, fish, and sports car design that went into the creation of these animals.


It is the liberty in splicing all of these disparate animals together that creature creators do to make a strange but believable fictional animal  that paleontology needs to take more inspiration from.

I think the Carr paper is valuable because it draws attention to crocodile skull texture. Yes it is true that tyrannosaurid skulls show some gross similarity to crocodile skulls in sharing a rugose texture and if you had to draw a rough comparison as to what animal best matches large tyrannosaur skull texture crocs are a good analogy. But crocs evince this rugosity all over the skull, tyrannosaurids have many smooth parts with the rugose sections being localized across more of the rostral sections. Of the animals presented above I would posit the Daspletosaurus skull as being the most different texturally from the others. People are naturally drawn to to comparing tyrannosaurids to crocodiles because they are related and predatory. However most theropods (except spinosaurids) are quite distinct from crocodiles ecologically. And that is the gist of what I am suggesting, we are potentially witnessing bone texture as an ecological signal - not as a phylogenetic/anatomical one. Instead of asking; what other archosaur skull looks most like a tyrannosaur skull? we should be asking; why does a crocodile skull look so similar texturally to a temnospondyl, catfish, snapping turle etc etc. skull? 

When we see a diverse array of animals exhibit a remarkable similarity in facial bone texture as well as a remarkable congruence of ecological niche - ambush predator of murky, aquatic haunts - we have to seriously question if this bone texture is really a phylogenetic-anatomical message or an ecological one. There is more than a reasonable and persistent trend of highly pitted, rugose, and textured skulls among aquatic and amphibious stealth/ambush predators. The question is why?

My hypothesis is that such skulls in aquatic predators - highly textured with increased surface area but still maintaining streamlining - work as enhanced sound/vibrational interceptors. Like an old, well used catching mit these rugose skulls are better able to intercept, transmit, and "grab" acoustical/vibrational frequencies in a visually limiting aquatic environment. Vibration may travel through tissues in different ways and bone might offer an added layer of frequency interception that - when combined with other tactile organs  (nerve endings, pressure domes, "whiskers" etc. etc. ) allows for a more comprehensive reading of the environment.

So why do tyrannosaurs - and many theropods - have such rugose skulls? Well in the case of spinosaurids (and maybe other theropods that exploited aquatic environments predominantly) it is possible they converged on a highly textured design for the same reason that other aquatic predators potentially did - it enhanced sensitivity. For most other other theropod skulls - including tyrannosaurids -  I would like to advance an argument from material science: that there is a relationship between bonding strength and surface roughness. In this case the two materials are skin and bone and a rugose bone texture allows for skin to better anchor on the skull - growing into all of the nooks and crannies with increased surface area - in light of a particularly traumatic bite prone existence. That this bone texture is most prominent on the parts of the "snout" most devoid of overlaying musculature and exposed to bites we should expect this rugose nature to be most prominent there. Which it is. Unlike a crocodile skull which displays rugose formations across almost all of the skull - in line with the potential use of such rugose formations to discern water borne vibrations.




Crocodylus porosus credit 
There is potential analogy to the textured skull of theropods acting as a structural adhesive to skin argument: hippo skulls. Animals which have tremendous lips and a very battle prone, bite weary existence. They don't have smooth bone where the lips and skin anchor - they have textured, rugose bone .

credit stock vault author Bjorgvin Gudmundsson

And for the record I do agree with Carr et al. (and Tracy L. Ford btw) that tyrannosaurids (& other theropods) did have exquisitely sensitive, tactile faces. But it was through large lips that grew out from the neurovascular foramina that these nerve endings felt and sensed their world - both the real time struggles of their prey and the touch of a mate or hatchling. It is patently obvious that the pattern of foramina on the dentary (bottom jaw) are arranged in such a way that the upper teeth will not cut into the labial tissue that grows out from them. Note that this is not the pattern we see the foramina take in the crocodile dentary - where they emerge right up next to the teeth.

I also agree that they were probably more romantic and tender than we might typically imagine.

Sources

Carr, T. D. et al. A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system. Sci. Rep. 7, 44942; doi: 10.1038/srep44942 (2017).online
Ford, T. L., 2015, Tactile faced Theropods: Journal of 
Vertebrate Paleontology, SVP 75th annual meeting, Meeting Program & Abstracts, 
p. 125.



"A Long habit of not thinking a thing wrong, gives it a superficial appearance of being right, and raises at first a formidable outcry in defense of custom". Thomas Paine


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Thursday, March 23, 2017

Gaslighting the Dinosaur: Just How Weird Can Dinosaurs Get?

Gaslight: Manipulate (someone) into questioning their own sanity by psychological means.

I've been wanting to write this post for a while but it was the revelation of two recent significant works that have crested into the perfect wave substantiating some undercurrent of sentiment I've been trying to crystalize in my brain cells.


Dinosaurs  might be getting a lot more unstable, contentious, and freakishly weird and unpredictable   before any type of normalcy and "consensus" view gains traction. Can you feel the instability under your feet?Are we in a post-fact dinosaur era?  What I have referred to as the dinosaur "weirdening" might also be understood as sort of a post-modern enlightening of dinosaur studies or even paleontology as a whole. For those that like to see things in black and white it might not be an especially pleasant road ahead for you. However for those that are willing to admit and forego their own biases; become comfortable with not knowing or better yet unknowing things; and have the audacity and humility to push forward regardless of nit-pickers, naysayers, and general haters these are indeed golden times in dinosaur studies.

What do I mean when I say we should have humility and audacity? Are not those two traits somewhat contradicting?

We should have humility in recognizing that the errors, oversights, and dogma in modern dinosaur paleontology occur just the same way that they did before the dinosaur renaissance. We might not be making the same errors, just a whole different batch of errors. What do I mean by this? Has not dinosaurs paleontology become a much more concrete science in the last couple of decades? Have we not dispensed with the ol' storytellers and "just so" charlatans of yesteryear? Paleontologists don't tell stories anymore - they measure stuff, compile data, and matrix things. Science the shit out of dinosaurs. Paleontology, and especially dinosaur paleontology, has evolved radically - one need only visit and talk to the presenters at the annual SVP conference to see the rigor and abstinence of speculating beyond the data, from telling stories.

The more evocative, dynamic Robert Bakker school of dinosaur paleontology has been supplanted by the more measured, rigorous "testable" prototype - what I refer to as the Lawrence Witmore protege  that dominates modern dinosaur paleontology. In fact I would trace this transition to a cover story in National Geographic magazine from March 2003 that documented the hardening of the arteries in dinosaur paleontology. Dinosaur science was no longer the place for story telling and whimsical notions.

"This is a good thing though. We need paleontology, and especially dinosaurs paleontology, to be a rigorous science. Good riddance to the Bakkerian notions that have plagued dinosaur paleontology"

Yes, but in eschewing the more story telling, fantastical, out there, "speculative" branch of dinosaur paleontology dinosaur science has lost it's soul. The arteries of paleontology have hardened and a plaque has formed limiting the flow of the true life's blood of dinosaur paleontology - imagination.

"Imagination is more important than knowledge. For knowledge is limited to all we know and understand, while imagination embraces the entire world, and all there ever will be to know and understand." - Albert Einstein

In the dispensing of story telling in dinosaur paleontology the science has lost something that it desperately needs to regain - something that the "All Yesterdays" movement addressed but must go even further with. All Yesterdays asked "what is the role of speculation in paleontology", however it was an open ended question and no concrete answer was given. The answer is two-fold I will suggest; imagination, new ideas, and concepts till the ground for new hypotheses, theories, and paradigms to emerge and; paleontology has changed - but people have not. As I said earlier many (not all) of the crop of top thinkers, paleontologists - teh luminaries if you will - are doomed to follow in the footsteps of the people that the dinosaur renaissance made look so foolish - not because they are foolish or stupid - they most certainly are not just as the people who were made obsolete by the dinosaur renaissance were not actually stupid. But there will be casualties along the way because people have not changed - even as the science has - because people are and always have been full of shit to various degrees. I'm full of shit, so are you reading this full of shit - we are full of shit because we have egos, biases, and groupthink is a thing that social primates do for good reasons until the bag of shit becomes soooo stinky someone has to ask what is that smell? What is that smell in dinosaur paleontology?

The Loss of the Narrative in Modern Dinosaur Paleontology and Why We Are Worse Off For It

Dinosaurs paleontology has largely forgot how to tell stories. How to narrate, how to blend science, art, and imagination into something truly uplifting, captivating, and mystical. The ability to take the mind and stop it. Not stop the mind in the sense of stop thinking - but simply hit it so hard you get a little stunned.

Ask yourself what got you into dinosaurs - was it a character matrix - or was it an evocative scene, picture, or vignette that hooked you? Paleontologists need to embrace storytelling and narratives once again. One doesn't need ignore or eschew the foundational science while also embracing the more mythical narrative ethos of paleontology.

As paleontology - especially dinosaur paleontology has shifted from the narrative - from "what might be" to "what we know for sure" it has left a void. Who tells the stories? If paleontologists don't create the stories that people hear about dinosaurs guess who does? The screenwriters of Jurassic World get to create the stories that people hear about dinosaurs that's who. And paleontologists have no one to blame for that but themselves for this predicament. Because say what you will about Bakkerian ideas - he sold them well enough - and those ideas, somewhat dated, still inform the Jurassic Park franchise to this day because of his craftsmanship.

I speak with the audacity that I do because I guarantee that my arch scavenger/hunter vulturine dromies would mop the floor with both those JP reptoid freaks & dapper ground hawks and absolutely traumatize audiences ; that a slow, creeping, silent assassin, super-senses endowed, night staking T. rex would send more shivers down the spine of movie goers than anything Hollywood or modern paleontology has came up with; that a bottom punting, water hunting Spinosaurus is the coolest damn thing you could have laid eyes on in the Cenomanian or in the local movie theatre; Allosaurs massing on a sauropod carcass, necks pistoning back and forth, rendering muscle, sinew, and bone, like some macabre gaggle of vultures on steroids. My dinosaurs would kick Spielberg's, Bakker's, Paul's, and Horner's dinosaurs asses combined. Fact. No freaking contest.

I mentioned earlier we should have the audacity to posit what dinosaurs were like. Now I might be wrong in some of my interpretations above, time may tell. But I have the audacity to posit such non-standard interpretations and defend them and create the wiggle room from which further studies may confirm or deny such ideas. More so than that a piece of evidence in favor of non-standard ideas might be overlooked without a framework for understanding new data in a different context. Saying nothing would be the greater wrong-doing than saying something that is later disproven.

Sauropods and Theropods Kissing Cousins No More….


Diplos for Allo Brunch by Duane Nash
Theropods and sauropods (evolutionary) friends to the end, or, maybe not? Sauropods decoupled from theropods while ornithischians and theropods linked into Ornithoscelida (Baron et. al. 2017). A good summary.

This work really is a game changer. For me the most interesting aspect of this - if it pans out and I have seen or heard of no strong counters to it as of yet - is the alarming amount of time the faulty saurischian/ornithischian split went on basically unquestioned.

I mean really guys? 

Now I buy a lot of technical dinosaur books. In these books I usually have to sift through like a ton of cladistic stuff before I can get to the snippet of mention of stuff  I am into like soft tissue, diet, behavior, ecology. The message I get is that phylogeny & cladistics is the "harder" aspect of dinosaur science and therefore gets more attention and pages. While diet, ecology, behavior, soft tissue falls under a more subjective and less rigorous banner presumably. Except now that I learn that the foundational dividing line separating ornithischians and saurischians might be hogwash, simply unquestioned dogma. Do you see where I am coming from? Teacher teaches without question student accepts blindly repeat ad nauseum…

That so many researchers focus on phylogeny and for this foundational aspect of the dinosaur family tree to go on seemingly unchallenged for so long, it does beg the question… are new thinkers being challenging enough? You need to be absolutely challenging and even somewhat combative against what your teacher is teaching you. And these same teachers need to love you for it.

Kaiju Dinosaur

Interestingly enough it is the revitalization of the kaiju film that offers more inspiration and hope for stoking the flames of dinosaur inspiration/lore than the dinosaur theme park movies at this point. Ironic that an explicitly fictional movie genre - kaiju films, literally meaning "strange beast" - is arguably offering more insight into dinosaurs than a film saga explicitly starring purportedly actual dinosaurs. Duane what the hell are you talking about?!?

Let us break down some commonalities between kaiju and macro-dinosaurs.

Kaiju lived for millennia and grew through multiple ontogenetic sequences. Dinosaurs lived for decades and occupied multiple ontogenetic ecological spaces. Jurassic franchise does not touch upon this concept. In fact in the Jurassic franchise fully grown dinosaurs seem to just inexplicably appear over night.

Kaiju can be seen as hoarders and harvesters of great mineral and energy wealth, they literally transform their ecosystem and form it to their will. Macro-dinosaurs likewise harvested caloric and mineral wealth from their ecosystem at vast scales in the process transforming the landscape. The Jurassic franchise does not touch upon this aspect.

Kaiju have two main reproductive strategies. Some, such as the Cloverfield monster, literally shed off replicating chunks of DNA in large batches. This closely matches the lay 'em and leave 'em strategy of sauropods. However most Kaiju have especially slow and low reproductive potential - seemingly at odds with how dinosaurs are now traditionally thought of as fecund r-strategists.


Or were dinosaurs such R-strategy specialists?

Indeed it is a stance that we need to constantly test and challenge. A recent paper illuminating the tremendous incubation time for the eggs of several dinosaur species  directly calls into question dinosaur fecundity and reproductive strategy(Erickson, 2016). Now this paper measured the incubation period of just two dinosaur species - Protoceratopos andrewsi & Hypacrosaurus stebegeri - which were revealed through careful analysis of incremental growth lines of embryonic teeth to have incubation periods of from 3 to 6 months!!   From this the authors speculated that such long incubation inhibited repopulation after cataclysmic events and that the bird off-branch of theropods (pennaraptora maybe?) was potentially unique in evolving relatively short incubation periods. That is their take home speculation, we will see how it pans out over time and if other dinosaurs indeed had such long incubation periods. Keep in mind if the unification of theropods and ornithischians solidifies then theropods having crocodile length incubatory periods may become a very tenable position.

My take home speculation is something else entirely, that if such long incubation periods were the norm for most dinosaurs - we will see - that potentially this shuffles the cards in favor of:

More intense pair bonding between male and female dinosaurs. It seems unreasonable that high metabolic females would do all of the nest guarding as modern female crocodiles do. After all 3-6 months is a long time to watch over eggs and taking turns over clutch guarding duties seems like a better solution. This also opens up a pandoras box of question in terms of mating fidelity, long term bonding, social cohesion, and perhaps given the stresses of a 3-6 month wait period perhaps females - or mated couples - only reproduced every other year, like some albatross species?!?

The nest as the foci for social, ecologic, and reproductive space. Keeping animals around a nesting space for 3 to 6 months is going to impose some pretty harsh consequences on the local landscape. Big dinosaurs could not fly or swim away to feed as nesting sea birds and marine mammal rookeries do. They were somewhat limited in how far they could travel and would experience diminishing returns as the immediate environment got depleted and longer foraging trips became cost prohibitive. Did they fast? Did mates bring back or regurgitate food stuffs for their partners? Some interesting questions there…

It is worth reminding ourselves that dinosaurs - if they did have crocodile length incubation periods - were not crocodiles. They were not slow metabolism, aquatic ambush predators that could simply lounge around and guard a clutch of eggs for 6 months eating very little or nothing. They also did not live for the 60 to 100 years like crocodiles, but had a much more restricted reproductive window. The clutches for dinosaurs were on the whole smaller than the clutch size of crocodiles. In short dinosaurs potentially had the long incubation span of crocodiles, further burdened with a smaller clutch size, shorter reproductive life span, higher metabolism and food/territory considerations, and exposure to predators/competitors/detrimental environment that caring for a nest for 3-6 months would entail.

Much of the reaction to the long incubation period has been skepticism or negating it on the premise that it covers only two species. Remember two species with long incubation periods is two more species than we have evidence for that exhibit short, avian length incubation periods... As I have already discussed with the dinosaur phylogeny situation, people are complacent with what they know or what they think they know. And what people have been shifting towards in the last couple of decades is that dinosaur nesting & reproduction was largely a lay 'em and leave 'em state of affairs with post hatchling parental care and investment limited at best. Sometimes even antagonistic especially with theropods. But this thinking might be due for a reboot.


How can you forget the M.U.T.O. (s) from the  2014 Godzilla reboot - the true stars of the movie? And it is in their reproductive ecology narrative that we can get some inspiration for dinosaur reproduction. A long trajectory into adulthood akin to the ontogenetic evolution of dinosaurs. Sequestering of tremendous resources - radiation for the MUTO - parallels the conquest for caloric and mineral resources dinosaurs sought. An epic, prolonged, and ritualized courtship. MUTOS had to call via echolocation for each other across continents - dinosaurs had to locate one another across long distances via low frequency calls. The choice of nesting grounds was not without its own burdens. MUTOS needed  their progeny to have a ready supply of radiation to feast upon. And dinosaurs needed to nest at a location that offered abundant resources for their own young. Even when a suitable partner was met, nesting site was located, abundant food in the vicinity, and eggs deposited things could go wrong. Godzilla could show up. Remember the heart-breaking emotive cries of the big momma MUTO when her clutch was destroyed? Epic battles ensued for both kaiju and dinosaurs because the reproductive stakes are that high.

In short I think that this work on egg length incubation is potentially as groundbreaking as the dinosaur taxonomy shake-up. Strangely, and I can only speculate on this, the egg length incubation paper did not receive nary the coverage or amazement as the ornithoscelida paper. Maybe we lack the framework for understanding just how much long incubation implies for dinosaur reproductive ecology. Personally I think it reshuffles the deck on many of the foundational conceits we make on many aspects of dinosaur behavior we take a little for granted. It really is that important in my opinion.

I also think that the small window of reproductive years, long incubation period, and intense competition for territory, mineral, and caloric resources at nesting locations compels us to look more and more at the possible prevalence of vocal, behavioral, and visual display structures in dinosaurs. Moods, intentions, and capabilities had to be conveyed clearly and explicitly at distance or in proximity. We already know of lots of evidence of display structures via skeletal structures but the scope and ubiquity of soft tissue structures across all dinosaurs is likely higher than generally assumed. Especially those soft tissues that can be inflated, engorged, and/or changed in color. Again, I and some others have long argued this, but the incubation work and its potential implications really crystalizes the high stakes nature of dinosaur social and reproductive ecology. It was a wild and wooly world - finite reproductive windows combined with finite resources created an anarchy of display forms and behaviors that we are just scratching the surface at.

The hedging in towards the safe and conservative becomes counterproductive if what you are studying - dinosaurs - are not actually safe and conservative. I think we are getting to that tipping point in dinosaur paleontology, where the outlandish and speculative is becoming more and more tenable, because we are in fact finally starting to concede that dinosaurs by their very nature were outlandish and not conservative.

Revelations by Duane Nash

Works

Baron MG, Norman DB, Barret PM (2017) A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature March 23, 2017

Erickson GM, Zelenitsky DK, Kay DI, Norell MA (2016) Dinosaur incubation periods directly determined from growth-line counts in embryonic teeth show reptilian grade development. Proceeding National Academy of Sciences vol. 114 no. 3 December 1, 2016

"A Long habit of not thinking a thing wrong, gives it a superficial appearance of being right, and raises at first a formidable outcry in defense of custom". Thomas Paine


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Monday, March 13, 2017

Plesiosaur Machinations XII: Shape Shifting Plesiosaurs & Marine Apex Predator Musical Chairs

Plying Abyssal Depths  by Duane Nash

The bull Albertonectes is down deep. Sweeping its massive 7 meter long neck - the longest among elasmosaurs and the most neck vertebrae of any tetrapod - back and forth it lights up bedazzling, psychedielic swarms of bioluminescent organisms of the deep scattering layer. Visible for more than a kilometer this banner of deep sea light plays a purpose for the animal. The elasmosaur is banking on the "deep sea burglar alarm" defense mechanism of the numerous and small denizens of the deep to draw in larger animals for the elasmosaur to ambush. 

The deep sea burglar alarm is a rather clever solution to predation in the dark vastness of the abyssal ocean. This theory rests upon the premise that for any predator of the ocean, there is often something bigger that is a predator of that animal. So if a prey animal is attacked in the dark depths a potential tactic would be to call in a larger predator to take out the animal attacking me. Hence the fabulous light show.

The bull is at home in the cold, crushing depths of the high Arctic Bear Paw Ocean. Despite the exertions from these provocations the massive elasmosaur - over 11 meters long and at 4 tons the weight of an Indian elephant - still has the capacity to remain under for at least 40 minutes. A deep rich blubbery layer and abundant super oxygen saturated blood provide the necessary equipment for such dives. With the ambient light provided by the bioluminescent organisms and pressure sensor receptors along the snout and the length of the neck the bull is well attuned to this environment despite the enveloping darkness. While matrilineal pods of Albertonectes ply the shallower oceans of the coastline these big males do their foraging in the deep, cool and productive water in order to gain weight and stamina over other males when the mating season begins. In those months the males feed rarely at all.

After the bull elasmosaur has litten up an area half the size of a football field it retreats over to the edge of light show, cloaked in darkness, and waits. He does not have to wait long for out of the blackness emerges another topside explorer of these depths. A primitive scromboid fish, itself equipped with advanced thermoregulatory features that allow it to exploit such productive but cold depths, has arrived to investigate the disturbance. At over a meter long the high octane fish - which usually cruises warmer and shallower water during the day in between dives - is usually met with a welcome feast when it investigates such scenes. And here is no exception as it voraciously ram feeds on the various cephalopods, crustaceans, annelids, jellies, and tunicates swarming in the melee. The visual detection of the fish is geared towards near sighted objects, 10 meters below it it does not see or feel the 11 meter long monster of the deep pivoting slowly into strike position. As the fish makes long and straight passes through the light show picking off small organisms the bull Albertonectes recognizes the pattern and anticipates. The fish is faster in the absolute measure of speed but if the elasmosaur can get within 7 meters it has a good chance of snatching it. Noiselessly and effortlessly the massive elasmosaur shifts and hovers into striking distance below the fish. Running along the length of the vertebral column is a channel filled with oils that allow the animal to change its position in the water column like a predatory stealth submarine. When the fish makes a pass hundreds of muscles fire simultaneously along the 7 meter ling neck drawing it upward and lateral to snatch the fish. These muscles, strongest at the base of the neck anchored along the neural spines and transverse processes, move the massive neck with astonishing speed and accuracy against water resistance. The necks purpose sole here to bring a relatively small but toothy mouth into a position to gain purchase. The fish now can sense the movement of a larger animal below it but here the neck of the Albertonectes outperforms the swimming muscles of the fish. A trailing fin of the fish is snagged by two inch long, deeply rooted fangs. As the bulk of the body of the elasmosaur catches up with the course of swimming the neck has set in motion the mouth opens quickly - the gape is amazing for such a small head - to reposition a bite on the gills of the fish. With bulldog like tenacity temporal muscles squeeze tight on the gills of the fish. 

400 meters below the surface of a cool, temperate Cretaceous Artic ocean the life of an ancestor to the tuna dies to support the life of a member of the most resilient and long lasting marine tetrapods ever.


Abyssal Fishing by Duane Nash

The plesiosaur machinations are back!!

As speculative as the above scenario is deep sea burglar alarms are a real thing and considering the ubiquity of bioluminscent organisms in todays oceans such defense tactics likely occurred in Mesozoic oceans as well. Plesiosaurs were probably right there to exploit them as the aquatic bad-asses that they were. Furthermore the take home message - that neck could have been used for all sorts of weird and useful tactics - should not be lost on people.

Because I have said it before and I will say it again: the long neck "plesiosauromorph" bauplan; guild; family - whatever qualifier you want to give it - is the longest tenured and most successful marine tetrapod family of all time. Especially if you go back and consider nothosaurs as part of the radiation plesiosauromorphs beat out macro-pliosuars, ichthyosaurs, sea crocodiles, placodonts, mosasaurs, sea turtles, any and all marine mammal/bird radiations in terms of longevity. Plesiosaurs just kept on sailing along flipping a proverbial middle finger (in the form of a long neck) to all those other marine tetrapod newbies as well as to future hominid interpreters all to eager to characterize plesiosaurs as misshapen, slow, downtrodden, backwards, weak, sucked up, ineffective, cumbersome, ecologically limited and forever the proverbial cannon fodder for the more ferocious, aggressive, and dominant mosasaurs, pliosaurs, ichthyosaurs, sea crocodiles etc. etc.

Changes in  plesiosaur perception are not unlike the revolution sauropods had to go through in the dinosaur renaissance. Early interpretations of sauropods depicted them as bipedally rearing, vigorous land animals. At least in attitude and countenance, if not anatomy, some of the earliest depictions and workers on plesiosaurs got more right than many more contemporary interpretations.






These are quite meme-tastic, no? Lifted from the Pinterest of Denver Fowler.

Far from being lackluster pushovers, these animals were likely highly combative and highly social and most likely combative as a social unit (like certain family oriented skinks) against perceived threats. You did not want big mama Terminonator mad at you because she probably has 5 other cohorts circling beneath and around you ready to take the fight to ya and bite you in all those sensitive areas'!!

These animals were sea monsters but they also may have had a sensitive side. The vastness, coldness, depth, and horrific indifference of the open ocean is an existential threat that every lineage of marine tetrapod has to face. Stare at the abyss long enough and the abyss stares back.



This daunting evolutionary challenge for slowly reproducing, high metabolism, social and air breathing marine tetrapods is most often met not only with tight and intricate social bonds but with reassuring physical contact. Plesiosaurs may have indeed eerily reminded us of sauropterygian equivalents to the highly evolved social marine mammals we are familiar with today.

ALL RIGHT, ALL RIGHT, ALL RIGHT!! Do I got the base riled up enough? Do I got ya' singing the sauropterygian gospel yet??

An incipient pivot has occurred. First and foremost people are really starting to take to this notion of plesiosaur being a lot more thicker... bring the thickness people. Not just thick layers of blubber and skin but absolutely daunting packages of muscles powering both fore and hind flippers - because the 2x penguin (credit Robert Bakker) - is a thing. And not just thick straps of muscle around the torso but thick necks - especially towards the base - are also getting traction.

Mark Witton recently wrote a piece Plesiosaur Paleoart: thoughts for artists in which he echoes a lot of the same sentiments I have been espousing in past plesiosaur machinations with regards to neck thickness, torso muscles, generally a more robust appearance. Make 'em thick.



credit Henry Sharpe used w/permission

And then pictures like this!! What the hell are those elasmosaurids investigating a potential meal larger than a trout breaking with the dogma of "they ate only small fish". Blashemy!!

Credit: © Jorge Blanco




What is this? A throwback of plesiosaurs battling eachother, necks flailing out of the water wildly?!? Restrain your skepticism, it could be that the body is supported from below as the animals are sitting on the seafloor?!?

Mauriciosaurus credit Frey et. al. 2017


A quick little shot out to thick bodied Mauriciosaurus being revealed; further work supporting the aristonectine radiation of filter feeding elasmosaurs; a polycotylid breaking the dogma of "obligate piscivore" and chomping on hesperonithinines.

Don't forget Heavens miraculous thick necked "eel" inspired Alaskan Talkeetna elasmosaur. Awesome work James!! GoFundME.



Yep it does seem like we are in a bit of a renaissance as goes plesiosaurs. And I do detect a faint whiff of plesiosaur machination inspiration in some of these newer interpretations. Long gone are the wimpy, clumsy looking, anachronisms of yore replaced by thick, muscular, confident, and awe inspiring sauropterygian aquatic monster-gods!! Rejoice!!

In light of all these new and wonderful discoveries and depictions of plesiosaurs I want to break with one of my own rules and depict a plesiosaur getting chomped on by another marine predator; not by a mosasaur; not by a pliosaur; not by a shark; but by an ichthyosaur!!

Attenborosaurus vs Macro-predatory Temnodontosaurus credit Duane Nash
I commit such travesty because 1) we don't have many images of macro-predatory ichthyosaurs doing dastardly deeds and 2) Attenborosaurus is one bad ass plesiosaur... urmm pliosaur... what is it?

With regards to point 1) on macro-predatory ichthyosaurs:


We don't often talk enough about macro-predatory ichthyosaurs because though was a big chunk of time in the Triassic to early Jurassic where the marine apex predator throne was held by these guys.  Perhaps due to the early and persistent comparison between dolphins and ichthyosaurs we have somewhat eschewed the monstrous and apex nature of some of these animals. I suspect that they were on the whole more sharklike in swimming motion, that they didn't "porpoise" through the water, and probably a little more opportunistic and "reptilian" in their feeding strategy than dolphins. It is a shame we don't have any living shark toothed dolphins around as they might offer better analogy...

I also did not ascribe a species name to the tempo but just went with a generalized large macro-predatory design. I depicted one of the temnos gulping down an immature Attenborosaurus in a swallowing feat many might be skeptical of.


Consider these points:

Modern animals - both with kinetic and akinetic skulls - swallow down quite sizeable things to a somewhat astonishing degree. We do tend to think of bone as quite rigid and "fixed" structurally but in the living animal it is wet and always has some capacity to deform - probably more so than we might assume from dried and brittle skeletal remains.

Ichthyosaurs, possibly due to their "dolphin" like assumed ecology, have been interpreted to have extremely stiff, unyielding dolphin like skulls or even quasi beaks. But look closely at the lower jaw i.e. mandible of ichthyosaurs - the two halves of the jaw, the dentary bones, do not form a solid connecting structure at the tip of the jaw. Unlike the mandibles of dolphins there is no mandibular symphisis.

T. platyodon no mandibular symphysis
Lyme Regis Ichthyosaur credit BNPS no mandibular symphysis

Could elastic tissue there allowed a certain amount of bowing of the lower jaw there to accommodate large parcels of food? Perhaps augmented by some amount of give along the length of jaw and at the jaw hinge? Even just a little flexure would have assisted swallowing large parcels of food… Additionally how rigid is the mandibular connection to the cranium? Could this have bowed out a bit? I don't know - not an expert - but I think there is enough there to ask: why not? Has adherence to ascribing dolphin like affinities to ichthyosaurs inhibited a more thorough investigation of their ecology and feeding apparatus?

hailing from Char mouth in Dorset U.K. T. platyodon credit Richard Austin

In case you have trouble wrapping your head around macro ichthyosaurs there is the pic above. I saw it on Facebook and thought that it needed wider exposure so I can't claim ownership or even permission to use it but in the spirit of spreading the word about these animals you will not find a better visual representation. T. platyodon may have been more of sperm whale than a killer whale, an idea we will revisit shortly. T. eurycehalus, though smaller, offers a more convincing glimpse at the skull of an apex predator ichthyosaur:

T. eurycephalus. credit Ghedoghedo. CC3.0
In addition to Temnodontosaurus and the various "species" that encompass that genus there was; Thalattoarchon saurophagis revealed a few years back; the mysterious, but potentially gigantic, Himalayasaurus; at the 2016 SVP meeting in Salt Lake City, Utah another massive macro-predatory ichthyosaur was announced hailing from British Columbia.

What is very interesting is that these top dog ichthyosaurs all seem to stem from the Triassic and early Jurassic and then they just peter out and disappear into the Jurassic. And this is a trend that seems to have parallel in many lineages of marine tetrapods that achieve apex predator status. An initial burst of diverse forms and then, over time, they wane off into... very often a niche of specialized deep sea teuthophagy (deep sea squid eaters). This is exactly the case with the formerly dominant and massive raptorial sperms whales as they are now represented solely by a dedicated deep sea squid eater. Could it be that many of the latter pliosaurids were actually specialized deep diving teuthophages? Always assumed to represent traditional pliosaur apex predator roles perhaps species such as  Brachauchensis lucasiMegacephalosaurus eulertiStenorynchosaurus; many of the other quasi polycotylid looking pliosaurs actually had more in common ecologically with sperm whales and pilot whales than killer whales.

Megacephalosaurus marine arch-predator or simply a celebrated squid eater?
Compare the skull of Megacephalosaurus eulerti (FHSM VP 321)- one of the last surviving pliosaurs - to a truly macro-predatorial skull below of Pliosaurus kevanni.


© Jurassic Coast Trust. Sir David Attenborough w/Dorset monster
Blasphemy right? Suggesting that not all pliosauromorphs were marine apex predators ready to go ape shit on any prey in sight… that some may have been more like sperm or pilot whales?

A constant theme of this blog has been unpacking the cultural baggage that comes along with analyzing  extinct animals that are in fact cultural creations. What do I mean when I say that extinct animals that absolutely existed are in fact simultaneously real and cultural creations? The term pliosaur is a loaded terms just as Tyrannosaurus or Smilodon are. When we think of a pliosaur we imagine a huge apex predator that smashed through lesser marine reptiles not necessarily a deep diving specialist on cephalopods… which many later pliosaurs may have been relegated to as sharks and mosasaurs crept into apex predator roles.

Megacephalosaurus eulerti credit MCDinosaurhunter CC3.0


I am not implying that titans like Pliosaurus necessarily evolved into more teuthophagous forms but that over time the apex predators got winnowed away leaving behind deep sea diving squid eating specialists. Life at the top of the photosynthetic marine food web was harsh and any disruption to the system potentially catastrophic for apex predators. However deep sea based food webs - dependent on detritus i.e. "marine snow" and/or chemosynthesis i.e. sulphur consuming organisms, tube worms etc etc. - may offer more stability than shallow water based marine webs dependent on photosynthesis. Which fits the pattern of diverse ichthyosaurs - including macro predator types - getting winnowed away leaving pelagic forms behind; raptorial sperms whales declining in diversity until just a single common teuthophage remains; macro-predatory pliosaurs getting diminished to teuthophagists. Extinct members of the walrus family were once a lot more diverse and some may have been highly predatory - now we are left with an arctic specialist of shelled mollusks. Shark toothed dolphins may have been much more broad in their ecology than most modern dolphins. I would not be surprised if a more predatory extinct penguin comes to see the light of day, if it has not already and we simply have overlooked it…

By the way I thought I would give some exposure to a rather excellent and thoroughly interesting Royal Tyrell Musuem video on the underreported swell of large apex sharks in Cretaceous with some interesting musings on which sharks might emerge as apex marine predators of future oceans.



What should become clear from the above video is how - when an oceanic apex predator declines - another group is waiting in the wings to fill that vacated niche. Nature abhors a vacuum.

So to summarize my thoughts on the matter and to paint with a very broad stroke I detect some common trends in several marine tetrapod adaptive radiations and extinctions:

1) Following large extinction event marine tetrapod clade diversifies rapidly including apex predator and deep sea diving forms.

2) Repeated environmental catastrophes usher in extinction events especially at the apex predator role. Deep sea teuthophage specialists remain relatively steady.

3) Invasions from other marine tetrapods into vacated marine eco-space inhibit reoccupation of niche space further winnowing away diversity. The last holdouts of formerly diverse radiations occupy offshore, deep diving, teuthophagist niches.

4) Large enough perturbations eventually kill off even offshore deep diving specialists rendering a full scale extinction of clade (i.e. ichthyosaurs, marine crocodiles, pliosauromorphs). Animals become so rare that loss of genetic diversity makes extinction a statistical eventuality.

Which brings us right back to the long necked plesiosaurs i.e. the "plesiosauromorph" bauplan. It just kept sailing along. While all of the other marine reptile clades fell away the plesiosauromorph dynasty just kept chugging along, a remarkably consistent pedigree of success.

We have to ask why?

I want to give that question room to breath a bit, I will come back to it in a future post. My current thinking is that plesiosauromorphs were exceptionally opportunistic not just in feeding but in habitat choice. The wide feeding envelop including everything from benthic organisms (clams, worms, crustaceans etc etc), mesopelagic fish/cephalopods, small/weak marine tetrapods, and scavenging combined with an exploitation of marine ecosystems ranging from deep abyssal offshore pelagic (as supported by histological evidence of "the bends") to estuarine/large river complexes offered strong resilience to environmental catastrophes.

And now finally on to point #2) Attenborousaurus is one bad plesiosaur or… pliosaur… what the hell is it anyways?

First things first how cool is it that this animal is named after Sir Richard Attenborough by none other than Dr. Robert Bakker. Back to the gist of the matter is Attenborousaurus a pliosaur or a plesiosaur? Well let us give it the 5th grade test. The 5th grade test is: "does this animal look like the Loch Ness monster?". The answer is unequivocally YES!! Phylogentically this animal is on the path towards latter true macro-pliosaurs that do fit our popular image of what a classic pliosaur does but - sheesh look at the neck - it probably has more in common ecologically and behaviorally with true long necked "plesiosauromorphs". A shape shifter caught in the act of shape shifting.

Attenborousaurus credit Adam Smith. plesiosaur directory
Yes, it is true that relative to other plesiosauromorphs this animal has a largish head. But in absolute size the head of this animal is not larger than many of the latter elasmosaurids and probably both were capable of the same predatory feats. In essence those that are ok with ascribing mesopredator tendencies to Attenborosaurus should ascribe the same tendencies to other plesiosauromorphs with similar sized jaws. An 18 inch skull with 2 inch teeth is just as effective on a 15 foot animal as it is on a 30 foot animal.

Attenborousaurus credit Adam Smith plesiosaur directory
What we see in Attenborousaurus is a trend towards the apex predator realm, essentially falling short due to the arch predator ichthyosaurs which still occurred in the Sinemarian. The shape shifting plesiosaurs would not be held back and that trend would continue into Rhomaleousaurus a truly impressive animal and perhaps our first best evidence of plesiosaurs making headway into apex predator territory.

credit Adam Smith. plesiosaur directory Rhomaleosaurus cramptoni w/curator Matt Williams. Bath Royal Literary & Scientific Institute

Something appears to have opened up the doors for sauropterygians to truly reach this potential. Let us look at a little time line here. Rhomaleosaurus dates to the Toarcian of the early Jurassic. Temnodontosaurus - the complex genus potentially representing the last of the macro-predatory ichthyosaurs - dates from the Hattengian to the Toarcian. Atennborosaurus occurs smack dab in the middle of apex predator ichthyosaur dominion, explaining why it did not become a truly pliosaur looking pliosaur. Could the waning macro-ichthyosaurs - perhaps already trending into deep diving offshore cephalopod specialists with some species of Temnodontosaurs - have allowed the proliferation of true macro-predatory pliosaurs? The suggestion is certainly there…

Or that is what I thought. Further investigation revealed that the daunting panappoly of late Triassic/Early Jurassic plesiosaurs revealed one early macro predatory pliosaur from the Hettangian age of the earliest Jurassic - what has formerly been referred to as "Rhomaleosaurus" megacephalus but which Adam Smith has cleaned up taxonomically as Atychodracon megacephalus. Things always tend to get more complicated the more that you peer into them. I still think that there was an interesting give and take between macro-predatory ichthyosaurs and the first macro-predatory pliosauromorphs. Perhaps the transition was already underway in the late Triassic?

Way back in the Triassic ichthyosaurs and nothosaurs were seemingly in a dead heat for that position as both scary huge Nothosaurus giganteus & N. zhangi occurred and coincided with macro-predaotry ichthyosaurs Thalattoarchon & Cymbospondylus. The ichthyosaurs appear to have won out, I don't know of any macro-predatory nothosaurs making it into the Jurassic. However sauropoterygian relatives of this vanquished class would eventually muscle in over the ichthyosaurs at the apex predator realm.

mandibular symphysis Nothosaurus zhangi credit Liu et al. 2014
Well I'm gonna leave it off right there. Probably a lot to think about; marine arch-predator musical chairs; shape shifting plesiosaurs; the consistent plesiosauromorph bauplan. I hope you enjoyed this and I hope you start to look at plesiosaurs with a new eye. I want to do one more post in the series, end it at lucky number 13 of course, and for this one I want to break one of my own rules: let me know if there are any topics or species I should cover for my last and final installment in the plesiosaur machinations and I will try to work them in. So I am taking requests in the comments.

best,

Duane



Some might be new to the plesiosaur machinations - allow me to indoctrinate. Or, if you have perused the evil machinations before, here is a quick summary and chance to review.

Yes Another Hypothesis on Long Necked Plesiosaur Feeding Ecology: In which I lay out rotational feeding i.e. twist feeding as a method to de-shell large ammonites. A little dated but possible...

Thus Spoke Zarafasaura In this post I lay the foundation for what eventually becomes the plesiosaur machinations by focusing on a particularly brutal looking elasmosaurs Zarafasaura; review plesiosaur art; death by quartering.

Plesiosaur Machinations I: Introducing the Plesiosaur Phalanx Attack

In the introductory post I discuss how a group foraging strategy would facilitate successful and efficient foraging for plesiosauromorphs; make the comparison between white pelicans and grey reef sharks; discussion on a wider prey envelope than generally appreciated; the shark genus Somniosus as a model for cryptic stealth technique.

Plesiosaur Machinations II: The Social Sauropterygian

In this post I advocate the familial unit as the basis for understanding plesiosaur ecology and behavior. I advocate several social lizards - especially skinks - as model organisms for how reptilian aptitude animals can establish social unity and cohesion. Anti-predator behavior is advocated to be antagonist and mobbing cooperative advancements against potential threats.

Plesiosaur Machinations III: The Family That Slays Together, Stays Together

Embellishing the social unity concept and exploring how simple biochemical feedback loops could have enhanced social unity merely through proximate physical contact. The long neck is proposed as an effective tactile appendage for physical contact.

Plesiosaur Machinations IV: He is the Last You'll Know…

Discussion on the feasibility of scavenging in plesiosaurs; plesiosaurs exploiting anoxic die off events; Meyerasaurus and Temnodontosaurus; Meyerasaurus proposed as analogous to oceanic white tip sharks.

Plesiosaur Machinations V: Despot Ammonite Slayer

Plesiosaurs feasting on ammonites, marine escargot…

Plesiosaur Machinations VI: WE BITE!!

Plesiosaurs and the misfits. Why you don't want to get bit by a plesiosaur. How many plesiosaurs fall outside the "obligate piscivore" morphology. Occitanosaurus being naughty. Mesopredator plesiosaurs.

Plesiosaur Machinations VII: You Can't Handle the Thickness

No more Jack Skeleton plesiosaurs. Make them thick and don't apologize for it. Stout muscular necks, thick torsos, plump tails, bulging "knot head" temporal muscles, and juicy blubbery layers. A machination classic.

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

We may never know the answer but I would not be so quick to dismiss… Another classic yet controversial machination.

Plesiosaur Machinations IX: In the Belly of the Beast

The varied and strange things found inside plesiosaur torsos. Includes my take on how a voided ichthyosaur embryo actually ended up in the stomach of a plesiosaur. 

Plesiosaur Machinations X: Senior Water Rights

Sauropods and plesiosaurs. Mosasaurs and elasmosaur arms race. Elasmosaurs prefer cooler waters. California elasmosaurs. Elasmosaurus vs. Tylosaurus revisited.

Plesiosaur Machinations XI: Imitation Crab Meat Conveyor Belt and Filter Feeding Plesiosaurs

The neck as a food storage device and aristonectine giant filter feeding elasmosaurids!!


"A Long habit of not thinking a thing wrong, gives it a superficial appearance of being right, and raises at first a formidable outcry in defense of custom". Thomas Paine


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