Burgers and Hot Dogs

Sydney Mohr is a friend and colleague of mine whose art you will have seen in the news lately, if you are inclined to read about ankylosaurs. She's done amazing reconstructions of two ankylosaurs for me in the last year - Ziapelta and Gobisaurus - and so I asked her to take a few minutes and tell us about her process for creating her palaeoart. Also this way I get to show off more of her drawings, so yay!

Sydney decided that this Gobisaurus was named Burger, and that seemed fine with me.

Once we got started on Gobisaurus, I sent Sydney a pile of photos of both Gobisaurus and its close relative Shamosaurus, and some of my own very rough sketches of what the osteoderms might have looked like. Gobisaurus isn't completely known, so we're guessing a bit on the osteoderm arrangement in the final version and using Shamosaurus for the cervical armour. Here are the earliest sketches Sydney sent me - so many great poses and personality. Also, here's a Sydney in her natural habitat (thanks John Acorn for the photo!).

  

One of the things I really like about your art is that it's obvious you are very familiar with animal anatomy and behaviour – your dinosaurs have real animal personalities. Can you tell us about some of your inspirations for your palaeoart? 

The best inspiration any artist can have when reconstructing extinct animals are...living animals! In most cases that's the best if not the only source of reference we have, at least when it comes to external appearances. Depending on what type of fossil I'm drawing, I'll try to find an extant analogue/s that may share some characteristics, like habitat and environment, diet, colour scheme, etc. For colour in particular I often mix and modify schemes from two or more animals, all the while keeping the fossil's apparent paleobiology and habitat in mind. I'll peruse images of modern animals on the web to get an idea of the posture and stance I want the fossil animal to be in, as well as the lighting and angle. A lot of a creature's emotion comes from the face, so I really like to focus on eyes. Getting the shape, depth, colour, and light just so can make a huge difference in terms of giving a drawing personality. It also isn't a bad idea to look at other artist's work, obviously not to copy directly, but you might get ideas for new methods or techniques that you can adopt and fit into your own style. 

Mr Iridescent - a beautiful take on Microraptor. So shiny and chrome.

This reminds me, I think you said the Ziapelta reconstruction you did for our paper was inspired by a photo of a bird that you took! And that in turn reminds me that you are also a pretty great bird photographer - do you find that you get a better sense for conveying personality and movement in your dinosaurs by observing birds in the wild yourself?

So I did! The proudest grackle ever! 

I can see the family resemblence! Also, when I found out the Gobisaurus was named Burger, I asked if the Ziapelta had a name. Naturally, it was Hot Dog.

And definitely, seeing any animal in their habitat first hand can create a narrative in your mind that you can translate to paper. Birds are great to watch because a lot of the time they're always on the move and engaging in a variety of behaviours that are both interesting and fun to watch, as well as perfect fodder for a dinosaur reconstruction.  

You are also working on a Masters with Phil Currie at the University of Alberta! Would you like to tell us about what you're working on?

The thought of Mesozoic birds with bonafide teeth has really interested me for a while, so the plan is to explore the evolution of tooth loss in birds by comparing the implantation and replacement rates of small theropod (like dromaeosaurids and troodontids) and bird teeth. Looking into the anatomy of the jaw and the inner structures of the teeth of these closely related groups will hopefully yield some informative results. It's not easy because the stuff I need is comparatively rare and pretty darn tiny! I'm working entirely with Alberta material at the moment, and doing so has led me in other directions in terms of understanding the province's Cretaceous avian fauna, which is most represented in terms of numbers by, you guessed it, teeth!

Pygostylia Panoply: at the bottom, the toothy Early Cretaceous enantiornthine Rapaxavis, and up top, the duck-like (and toothless) Presbyornis.

Do you have a favourite taxon to illustrate?

Birds and feathered theropods are definitely up there.The more I do ankylosaurs though the more I enjoy drawing them. [YES FOLKS, YOU HEARD IT HERE: ANKYLOSAURS > THEROPODS.] They're so unique compared to anything else around today! I also enjoy doing mammals as well, like ungulates and carnivores (fossil or modern) and primitive examples from the Mesozoic. 

I am but a young'un: a perfectly floofular dromaeosaur chick. 

What medium/media do you like to work in?

I stick almost exclusively to traditional media; mainly pencil work, both black and white and colour, although I occasionally work in acrylic or watercolour. I prefer to work with fine tooth paper so I can vary my pencil strokes, blend more easily, and just have an overall smoother surface to work on. Coloured paper is also really fun to work with, like blue or black, because it makes drawing ocean scenes with pencil pretty simple. I've also dabbled in digital art via photoshop, but most of the time I only use it to fix mistakes and touch up scanned pencil drawings. In my case I find I have much more control with pencil and paper, and the results seem to be a bit more realistic, at least to my eyes. 

Ichthyornis dispar: a classic fossil bird, brought to life!

Do you have any advice for other people who are interested in creating their own palaeoart? Any common pitfalls to avoid, or things to think about when they are recreating an extinct animal?

I think one of the most important aspects of reconstruction is attention to detail, such as the dot of light and reflections in an eye, or the wind disturbing and ruffling fur or feathers, or the bulge of a muscle as a limb is flexed, or the crumpling of skin as it moves in a certain direction or shifts under the weight of the animal. Light, movement, and substance. Those kinds of little and almost unnoticeable features can take a simple reconstruction of a fossil to something that feels tangible and alive. In terms of pitfalls to avoid, I would say there isn't too much to worry about if you're just playing around and having fun, because hey, it's just art! That being said, if you're going for a publishable, as-accurate-as-possible, realistic style of depiction, then it's a good idea to become familiar with your subject, especially anatomy. If you can read up and get as close as possible to the original source material, like scientific papers, then you're that much closer to getting your skeletal anatomy down pat. Knowing some anatomy of modern animals is extremely helpful as well, as it informs how muscle and skin attaches to the bone and changes the outline of the body.

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Thanks Sydney! You can check out more of Sydney's amazing art and photography at her website, DeviantArt gallery, and Flickr gallery.

Gobi Desert Diaries: Nemegtomaia Edition

Today I've got five questions for Federico Fanti, the lead author on a paper published a few weeks ago in PLoS ONE on a nesting oviraptorosaur. I first met Federico during the 2007 Nomadic Expeditions Dinosaurs of the Gobi expedition, in which we all had a grand time prospecting for dinosaurs and during which we celebrated a fine discovery indeed.

1. What inspired you to conduct this study?

Well, the fossil itself! I grew up with incredible pictures taken somewhere in the Gobi Desert of Mongolia, with spectacular fossil remains literally emerging from the vermillion sand. When Phil Currie and I realized that we were looking at a nesting dinosaur we were simply happy and enthusiastic: there are only 5 specimens of brooding dinosaurs known to date in the world, it is a unique find. I couldn't wait to find out more about this specimen and finally, after more than four years, I'm glad to see the paper out.

 

(MPC-D 107/15 diagram from Fanti et al. 2012, by Marco Auditore.)

2. Nemegtomaia is not exactly a household dinosaur name. Who is Nemegtomaia?

Nemegtomaia means "good mother of the Nemegt" and curiously the name was chosen long before our discovery. In the '90s, the type specimen - including a nicely preserved skull - was collected from the Nemegt Formation not far from where we found the nest: however, no trace of eggs or nest were found at the time. The discovery of MPC-D 107/15 (or Mary, as I still like to call it) definitely supports the choice of Nemegtomaia as the name for this species. Nemegtomaia is a genus of oviraptorid dinosaur that inhabited what is today southern Mongolia during the late Cretaceous period, approximately 70 million years ago. It is characterized by a well-developed crest on the skull and relatively short forelimbs with robust claws.

(Nemegtomaia skeleton reconstructions from Fanti et al. 2012, by Marco Auditore.)

3. What's so special about MPC-D 107/15?

Unlike all other nesting dinosaur that have been discovered so far, this specimen has a nicely preserved skull and therefore it was possible to reliably refer MPC-D 107/15 to the genus Nemegtomaia. Furthermore, within the context of the Nemegt area where dinosaur eggshells are frequently recovered, it was possible to refer a specific egg type to this genus. In addition, the preservation of the forelimbs allowed us to reconsider the classification of this genus within the oviraptorosaurs: unlike many other oviraptorid species, in fact, Nemegtomaia has relatively short and robust forelimbs, indicative of different adaptations and behavior.

4. In the acknowledgements section of the paper you note that MPC-D 107/15 was excavated 'under what were at times difficult circumstances'. How did you find this specimen, and what were the challenges in excavating it?

I found the specimen while prospecting in a sayr, a canyon located not far from the Camp. It was barely cropping out from a vertical cliff, about 3 feet from the valley ground. A section of the nest and of the pelvis was visible at the time, meaning that, with the exception of the tail, the skeleton was still preserved in the cliff.

(Federico did well to spot the nest, which was hardly exposed at all in the surface - just eggs and legs in cross section.)

It took a full week and the work of several people to take it out, and I must thank all the people that participated in the 2007 fieldwork (including the author of this blog! [aw, shucks - VMA]) for the help in the field.

Difficult circumstances? A mix of heavy rain, collapsing blocks of sandstone alternated with 45 degrees in the shadow are .. interesting circumstances!

(Although I didn't spend much time working on the nest excavation, I do know what Federico, Phil, and Badam are referencing when they say 'difficult circumstances'. On the second-to-last day in Nemegt, the skies opened and it poured rain ALL DAY. The nest had to come out the next day, so a team went out to the site and worked under a tarp all day in the soggy, soggy desert.)

5. What does this specimen tell us about the nesting habits of oviraptorosaurs?

Nemegtomaia has been collected in both the Baruungoyot and Nemegt formations, which are representative of aeolian/desertic and fluvial environments respectively. This indicates that Nemegtomaia was a long-living genus and adapted to different environmental and climatic conditions. The nest preserves approximately 20 eggs: we know from other spectacular specimens of oviraptorid dinosaur that they were able to laid 2 eggs at time, thus we assume that different individual laid their eggs in a single nest. As a consequence, the animals that we discover in brooding position are not necessarily the parents nor the mothers. It is possible that a male was "selected" for parental care during early development of embryos.

If you haven't yet read Fanti et al. (2012), go get it right now for free from PLoS ONE! Thanks Federico!

Fanti F, Currie PJ, Badamgarav D. 2012. New specimens of Nemegtomaia from the Baruungoyot and Nemegt Formations (Late Cretaceous) of Mongolia. PLoS ONE 7(2): e31330.

5 Questions for Phil Bell

Hot on the heels of yesterday's interview with Caleb, here's an interview with Phil Bell of the Pipestone Creek Dinosaur Initiative. Phil is a former Currie Lab member who completed his PhD last spring, focusing on the Mongolian and North American hadrosaur Saurolophus. He recently published a paper on skin impressions in Saurolophus. Thanks to David Lloyd of the Tyrrell Museum for the great photos of work at the Dragon's Tomb in 2010!


1. What inspired you to conduct this study?

Actually, it was entirely by accident. Like so many advances in science, it came from an unresolved problem: were these two species of Saurolophus (S. osborni from Alberta and S. angustirostris from Mongolia) actually different or were they the same thing? I was at the American Museum in New York in the process of looking at the bones and skeletons of Saurolophus to try and answer that question. I mean, that’s what you do if you work with dinosaurs, you look at the bones. But I immediately struck upon a load of skin impressions. Like most people before me, I thought “that’s cool” but being the first time I had worked with skin impressions, I took the time to photograph, and draw, and measure the hell out of them. When I got to Mongolia later that year, I had the chance to visit one of the great (but little known) palaeontological treasures of the world, the Dragon’s Tomb (see Q3). This site preserves a herd of ‘mummified’ Saurolophus and you can still find loads there today. It was here that I started to notice differences in the skin impressions between the two species and from there I began my search for more specimens with skin impressions that have been stashed in museums from Mongolia, Poland, to Russia.

Phil with a block of Saurolophus at the Dragon's Tomb, Gobi Desert, Mongolia, 2010.

2. Who is Saurolophus?

Saurolophus is a hadrosaur or duck-billed dinosaur. Like it’s more famous cousin, Parasaurolophus (which actually means, ‘like Saurolophus’), it had a rod-like crest sticking out of the back of its skull, but unlike Parasaurolophus, this crest was solid. There are two species: Saurolophus osborni from Alberta grew to around 10 m in length, whereas the Mongolian Saurolophus angustirostris was a giant growing to 12 m in length.

Phil at the Paleontological Institute in Moscow in 2010.

3. What is the Dragon’s Tomb?

The Dragon’s Tomb is the name given to a site discovered by Russian palaeontologists (well, actually, it was one of their drivers who found it) in 1947 in the heart of Mongolia’s Gobi Desert. When they arrived, they found not just one but six or seven Saurolophus skeletons lying on a rocky ledge, most with skin impressions. The Russian’s named it the Dragon’s Tomb for obvious reasons and since then many more Saurolophus skeletons have been found there. Unfortunately though, fossil poachers have also relocated the spot and have caused irreparable damage by using dynamite to blast out skulls and skeletons to sell on the black market. But the place is so rich you can still find great stuff there. I’m involved in a project with Michael Ryan (Cleveland Museum) and David Evans (Royal Ontario Museum) to further explore this site and to figure out why exactly tens of Saurolophus died there.

The Dragon's Tomb, Gobi Desert, Mongolia, in 2010.

4. What is special about the skin of Saurolophus?

Well, for the moment it’s the most complex scale pattern ever seen in a dinosaur. People have known of dinosaur ‘mummies’ for 100 years (actually, last year was the 100^th anniversary of the discovery of the first, and in my opinion the best ‘mummy’ ever found; that of Edmontosaurus now on display in New York) but the complexity of their scale patterns has not been really appreciated until now. The stripy pattern on the tail of S. angustirostris was a complete surprise – one that I didn’t even believe when I first saw it. I thought it was a trick of the light or something to do with how the animal was preserved. But when I started to see it on more and more specimens, there was no denying it.

Preparing latex molds of skin. Fittingly, the latex brand is called "Dragon Skin".

5. Can different scale patterns tell us anything about the colour or colour pattern of Saurolophus?

That’s always a tricky question but without the actual colour preserved (as some people have shown with fossilized proteins that produce pigment) we can never be certain. One way of testing that question is to look at modern animals with scales (crocs, lizards, snakes). If you look closely at any of these animals you will notice that not all scales are born equal – some are big, some are small, some are long, circular or hexagonal. And they all have a function of some kind. Take a snake for example; most of the scales along its back are diamond-shaped and coloured in some way. But look at its underside and the scales are really wide, spanning the entire width of the animal, which they use to grip the ground when they’re on the move. They’re also usually a different colour to the top side. So, different shape, different function, and different colour. I’m not saying this is the way it always is but it’s a pretty compelling notion wouldn’t you say?

Thanks very much, Phil!

You can read the original paper here:

Bell PR. 2012. Standardized terminology and potential taxonomic utility for hadrosaurid skin impressions: a case study for Saurolophus from Canada and Mongolia. PLoS ONE 7(2): e31295.

And also see "Saurolophus skin suggests speciation" at Superoceras, and "Judging a dinosaur by its cover" at Dinosaur Tracking, for more coverage of this paper.

5 Questions for Caleb Brown

I'm very pleased to present another UALVP-related study today, this time by Caleb Brown (formerly at the University of Calgary and now at the University of Toronto). Caleb recently published a paper in PLoS ONE featuring one of my favourite UALVP specimens, our Stegoceras partial skeleton, UALVP 2.


1. What inspired you to conduct this study?

I was initially interested in pachycephalosaur postcranial anatomy for the purpose of differentiating between isolated pachycephalosaur postcranial material and those of basal ornithopods (like Thescelosaurus and Parksosaurus), on which I was doing my Masters research at the University of Calgary with Anthony Russell. In order to get a better understanding of the postcranial anatomy of these animals I went to the source, Stegoceras - UALVP 002, one of the best (if not the best) pachycephalosaur skeletons known, and the first postcranial skeleton discovered. In addition to other things, I was initially struck by the presence of large numbers of bony elements that I could not identify and that did not match the morphology of other ornithischians.

 

 

These elements looked superficially like gastralia, and indeed that is what they were identified in Gilmore’s 1924 description. But ornithischians were not supposed to have gastralia, so my interest was peeked. Investigation into the literature revealed that others had worked on these enigmatic elements; Marya´nska and Osmólska (1974) found similar elements in the tail of Homalocephale in Mongolia, illustrating they were not gastralia, and Sues and Galton (1987) correlated the structures between Homalocephale and Stegoceras. Particularly interesting was the articulated series found in the tail of Homalocephale. These showed a distinctive pattern that matched myomeres and myosepta, the sideways “w” shaped muscles and tendons, seen in fish.

Fortunately, with funding from Lubrizol Corp. and Montessori High School (University Circle, Cleveland, OH) I was able to accompany Michael Ryan (Cleveland Museum of Natural History) and David Evans (Royal Ontario Museum) to Mongolia to do fieldwork in the summer of 2009. I was also fortunate enough to be able to examine the Homalocephale specimen while I was there. This allowed me to test my ideas about the deep homology of these interesting structures.

2. What’s so special about pachycephalosaur tails, anyway?

First off, pachycephalosaur tails, like the rest of their postcranial skeletons, are rare. Often with dinosaurs you find the rest of the skeleton but are missing the most important part, the head. This is not true for pachycephalosaurs, which we know almost everything about based on the skull. You can count on one hand the number of partial skeletons known (and these are partial skeletons). What we know about pachycephalosaur skeletons is limited to these few specimens. They are special in that when preserved they show a unique morphology of having a halo of superficial “W” shaped elements forming a cylinder around the entire circumference of the tail. This is not seen in other dinosaur groups, or any other tetrapod. That is not the only odd thing though; they lack the deep longitudinal or paraxial tendons seen in most other ornithischian groups and they have elongated and highly bowed caudal ribs.  These three things may be related, but that is not yet clear.

3. What is the difference between gastralia, ossified tendons, and ossified myorhabdoi?

This is an interesting question with a bit of a complex answer. All of these structures are similar in that they are not endochondral bones, that is they do not develop from a cartilaginous precursor, which is the case with the majority of the postcranial bones in most taxa.

Gastralia are dermal or intramembranous bones that are associated with the abdominal musculature, and can be associated with respiration. They were likely the primitive condition for tetrapods but today are restricted to Crocodylia, Sphenodon, and possible the plastron of turtles (Classens, 2004).

The term ‘ossified tendons’ describes a variety of structures including ossified myorhabdoi. Although this term would include any ossification of the connective tissues articulating muscles to bones, its usage in dinosaurs, particularly ornithischians, usually refers to longitudinal paraxial structures along the dorsal or caudal vertebral series. These tendons often have the pattern of either a trellis or longitudinal bundles, can be epaxial or hypaxial, and are usually closely associated with the vertebrae (Organ 2006). Ossified myorhabdoi are restricted to the caudal musculature, and are essentially ossified myosepta. Unlike the majority of the paraxial tendons, these are superficial, forming a halo around the circumference of the tail where the transverse skeletogenous septum intersects with the integument, and preserve a morphology reminiscent of the undifferentiated myoseptal musculature of fish. They are also different in their histological structure (Organ and Adams, 2005). We still know very little about ossified myorhabdoi and hopefully discovery of additional specimens and more research on extant taxa will reveal more regarding their significance.

4. Why don’t other dinosaurs have a caudal basket?

It is often hard to answer why some groups have a structure while other don’t, and this becomes particularly difficult when the function of the structure is not fully understood. If the function of the ‘caudal basket’ is to rigidify the tail of pachycephalosaurs, then the reason that other groups don’t have it is because many have found a different solution to the same problem.  Many other ornithischians have longitudinal or paraxial tendons (usually called “ossified tendons”) in the form of a trellis or bundles. Some theropods stiffen their tail by extending the zygapophyses across numerous vertebrae. Until the function of these structures can be better established, we may not know the full significance of their occurrence.

 

5. Does the presence of a caudal basket tell us anything about head-butting behaviour in pachycephalosaurs?

The caudal basket likely had significant implications for the posture and locomotion of pachycephalosaurs. It has been suggested by previous authors that it helped the tail to act as a tripodal prop, potentially during intraspecific behaviour. It would also have greatly stiffened the tail. Our analysis is consistent with these interpretations, and in that manner is consistent with the idea of head-butting behaviour in pachycephalosaurs. 

The presence of the caudal basket has also been used to support the idea of agonistic flank butting behaviour in pachycephalosaurs (Goodwin et al., 1998), with the caudal basket acting as armor. We suggest that the morphology of the myorhabdoi is not consistent with armor seen in other groups, and this function in pachycephalosaurs seems unlikely.

Thanks very much Caleb! You can read more about pachycephalosaur tails in:

Brown CM, Russell AP. 2012. Homology and architecture of the caudal basket of Pachycephalosauria (Dinosauria: Ornithischia): the first occurrence of myorhabdoi in tetrapoda. PLoS ONE 7(1): e30212.

5 Questions for Stephanie Blais

I'm hoping to feature some more University of Alberta-related research over the next few weeks, and first up is an interview with Stephanie Blais, a UALVP grad student studying ischnacanthid acanthodians. Stephanie recently published a paper in the Journal of Vertebrate Paleontology with new information on the origin of vertebrate teeth. So without further ado, here are five questions for Stephanie Blais:

1. What inspired you to conduct this study?

This particular study is really just part of a general interest in the origins of teeth. I don't know if anything really "inspired" it per se, but I've always been interested in teeth as indicators of ecological role, and never really thought about how they originated, and then I learned that nobody actually really knows how they evolved. Which is weird, because they're so widely studied and they're probably the most numerous vertebrate fossils out there! So I decided to look at fossils of some of the oldest animals with 'true' teeth, and noticed some of the specimens from the MOTH locality (NWT) have weird tooth-like scales, which is where this study came in.

The next step is to figure out what function these may have had, and also to look at the other kinds of early gnathostome (jawed vertebrate) teeth and see how they are related.

2. What are the inside-out and outside-in hypotheses all about?

These are the two main hypotheses about the origin of the vertebrate dentition. They're hard to sum up without getting into a lot of evo-devo, and they touch on quite a few points, but I'll try. It's also difficult to explain both without bias, but I'll give it a go. Bear with me.

Basically, the 'inside-out' hypothesis suggests that the developmental machinery that produces teeth originally evolved in the pharynx of jawless vertebrates and eventually became transferred to the oral cavity. This would mean that teeth evolved before jaws. Proponents of this hypothesis have also suggested that conodonts (which lacked odontodes or any form of external denticles or armor) had the first vertebrate teeth, and this would mean that pharyngeal denticles and external denticles have completely different evolutionary histories.

The opposing 'outside-in' hypothesis is that teeth are essentially modified head scales that became specialized along the margins of the mouth in early jawed vertebrates (so teeth evolved after jaws). According to this hypothesis, internal and external denticles share a common evolutionary origin. A modified version of this hypothesis suggests the pharyngeal denticles in some thelodonts developed due to migration of cells or tissue with odontode-producing potential from the outside of the body to the pharynx through the branchial openings.

3. What are ischnacanthid acathodians, and what do they tell us about the evolution of teeth?

 

Ischnacanthids are members of a larger group of small, spiny fishes called acanthodians, which are related to both sharks and bony fishes. They are interesting because they have many kinds of dentition, although they're unique in having special dermal tooth-bearing bones in their jaws. They're also interesting because there are articulated Ischnacanthids from the Silurian, with well-developed teeth. Although other groups had teeth, we mostly find disarticulated specimens or, more often, isolated teeth and scales. The development of their dentition is more difficult to puzzle out, and that's what I'm interested in. Study of ischnacanthids, other primitive acanthodians, and shark-like fishes from the Silurian and Early Devonian can hopefully help us to understand how the first teeth developed, and how different kinds of early teeth are related to each other.

4. What is so special about the MOTH locality?

The MOTH locality is one of the best sources of Early Devonian fish fossils in the world. Hundreds of specimens, from over 70 different species, have been collected from this one site in the Mackenzie Mountains. What really makes MOTH outstanding, though, is that a large proportion (I don't know if it's been figured out for the whole assemblage, but it's probably around 40-50% for acanthodians) of the specimens are of articulated, complete or nearly complete fishes. That is probably partly due to sampling bias, but that's still hundreds of articulated specimens. And a lot of those are perfectly preserved down to the nodes on the ridges on their (microscopic) scales!

As far as ischnacanthids are concerned, articulated specimens of this quality are pretty much unheard of anywhere else. Usually you only find their isolated jaw bones, maybe with a bit of jaw cartilage attached if you're lucky. There have been articulated ischnacanthids described from other localities, but none are as well-preserved as those from MOTH.

5. And finally, because it is a law that all palaeontological news stories must eventually come back to T. rex...what does this study tell us about the teeth of T. rex?

You know, surprisingly, the journalists I have spoken to (all two of them) didn't ask about T. rex. They did ask how these tooth-like scales relate to our teeth though - maybe there are two options to the law - T. rex and/or humans?

Regarding T. rex, I guess my answer will depend on what, if anything, I find out about tooth homology among early gnathostomes. If ischnacanthid teeth are homologous to bony fish teeth, then they could be regarded as the "tooth ancestors" of T. rex teeth, without which T. rex wouldn't have been able to Rule The Dinosaurs! ... And which of course would then make them valid for paleontological study. I rather think they might be.

Thanks Stephanie!

Blais SA, MacKenzie LA, Wilson MVH. 2011. Tooth-like scales in Early Devonian eugnathostomes and the ‘outside-in’ hypothesis for the origins of teeth in vertebrates. Journal of Vertebrate Paleontology 31:1189-1199.

Junk in the Trunk Redux

Today I've got another interview from Scott Persons! Scott's going to tell us all about his new paper on the tail of Carnotaurus, which follows his paper on the tail of Tyrannosaurus published last year. Enjoy!


[Persons WS, Currie PJ. 2011. Dinosaur speed demon: the caudal musculature of Carnotaurus sastrei and implications for the evolution of South American abelisaurids. PLoS ONE 6(10): e25763.]

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1. What inspired you to conduct this study?


This was a case where no inspiration was required, just thoroughness . . . and a pinch of luck. My work on Carnotaurus was part of my Master’s thesis, which looked at the tail morphology of a wide range of carnivorous dinosaurs. Carnotaurus, a member of the unusual abelisaurid group, was on my list of potential dinosaurs to examine. The first Carnotaurus material that I saw was a cast at the Natural History Museum of Los Angeles County. Examining the L.A. Carnotaurus cast fit in nicely with my schedule, but I was in California primarily to measure the tail of a Dilophosaurus skeleton at Berkley.

Fortunately, it only takes one look at a Carnotaurus tail vertebra to realize that something dramatically weird is going on with the animal’s tail.  On a “normal” theropod tail vertebra (or, for that matter, a “normal” anything-else tail vertebra), boney projections, called the caudal ribs, stick out horizontally and have a simple rod-like shape. In Carnotaurus, the caudal ribs of the basal tail vertebrae project more vertically than horizontally, and their shape is complex – with tips that are thin and shaped like half-crescents. After examining the specimen in California, I realized how interesting a Carnotaurus tail study would be, and it became a major focus of my research (which meant Dilophosaurus and several other theropods had to take a backseat).

The 6^th tail vertebra of Carnotaurus, as seen from the side (upper left), the front (upper right), and from above (lower center).

2. Why “speed demon”?

The title of the Carnotaurus tail paper (published in the online scientific journal PLoS ONE) is "Dinosaur Speed Demon". It is an unusual title. Supernatural fiends (fast or otherwise) and peer-reviewed natural history literature don't usually mix. But the explanation is straightforward:

Carnotaurus is famous for its ugly mug and two large conical horns that stick out from its forehead in an indisputably devilish style (hence “Demon”).  As for “Speed”, the conclusion that I and Dr. Phil Currie came to was that the vertically oriented caudal ribs and their bizarre half-crescent-shaped tips (which interlocked with those adjacent in the vertebral series) provided an expanded and ridged framework for one super-sized tail muscle: the caudofemoralis. The caudofemoralis is a locomotive muscle that attaches to the femur and lends considerable force to the power strokes of the legs. Except for some birds, all dinosaurs had caudofemoral muscles (that’s a major reason why dinosaurs have big tails), but I estimate that, relative to its body-size, Carnotaurus had the biggest.

A new Carnotaurus illustration created for the paper by artists Lida Xing and Yi Liu.

Big locomotive muscles mean more locomotive power, which means Carnotaurus was adapted for speed.  Some puns are too good to pass up.


3. So...could Carnotaurus outrun the Jeep in Jurassic Park?

Estimating the maximum running speed of a dinosaur or any other extinct animal is hard. (So hard that in the published paper, I stick to offering a qualitative rather than a quantitative assessment of Carnotaurus running performance.) There are lots of important variables besides absolute muscle mass that determine how fast an animal can run.

As I said in my previous blog post, just keeping pace with the JP Jeep would require a speed of 30-40 mph (48-64 kph) (remember, the black-leather-clad rump of a certain chaotician was preventing the driver from switching into high gear).  So, achieving Jeep-catching speed would mean a charging Carnotaurus was roughly 30% faster than a charging black rhinoceros – a scary thought, but not an implausible one. If I had to guess, I would say: Yes, Carnotaurus was fast enough to outrun the Jeep. Just the same, I don’t think Carnotaurus would have caught it. Here’s why:

The tree branch doesn’t move, and the T. rex doesn’t appear to see it.

Jurassic Park fans will recall that in the chase scene, just as the T. rex is getting close enough for Jeff Goldbloom to feel its hot breath, the Jeep drives under a low tree branch. Being the colossus that it is, the Tyrannosaurus just smashes through the branch and stays on course. At roughly one third T. rex’s size, Carnotaurus probably couldn’t do that. Instead, the abelisaurid would have had to avoid the collision. While my study indicates that Carnotaurus was evolutionarily engineered for speed, it also indicates that this speed came at the cost of turning performance.

The rigid framework provided by the interlocking caudal ribs would have limited sinuous motions, which would have disadvantageously increased the animal’s effective rotational inertia. When turning, Carnotaurus would have been forced to awkwardly swing its hips and the front half of its tail all at once, like a single stiff board. The set of a tropical Hawaiian forest just isn’t the ideal hunting ground for Carnotaurus, and I think having to swerve around the foliage would have slowed Carnotaurus down considerably.


4. Does this tell us anything about the evolution of abelisaurids?

Yes, but exactly what it tells us is a matter of debate.

Abelisaurids are known from Africa, India, Madagascar, and South America. Carnotaurus is from South America. If you look at the tails of older South American abelisaurids, you will see what I think is a clear evolutionary sequence of adaptations in the vertebrae that leads to the advanced form of Carnotaurus. I would argue this shows that, over time, South American abelisaurids were getting faster. I would also argue this strongly suggests that Carnotaurus is more closely related to other abelisaurids from South America than it is to abelisaurids from Africa, India, or Madagascar (all of which lack special tail-vertebrae adaptations). The argument is important, and a matter of contention, because it has been previously asserted (by paleontologists much more experienced than myself) that Carnotaurus is most closely related to abelisaurids from outside South America.

The evolution of South American abelisaurid tail vertebrae through time (each vertebra is depicted in frontal and top-down views, numbers are millions of years from now).

 

5. Carnotaurus may not be as famous as Tyrannosaurus, but it has popped up occasionally in film and TV. What are your favorite portrayals of Carnotaurus?

Yeah, Carnotaurus has had its chance in the spotlight, probably because its striking facial profile makes it a natural fill for villainous roles. Picking my favorite portrayals is hard . . . because most have been so terrible.

In Michael Crichton’s second Jurassic Park novel, a Carnotaurus pack poses a threat to the inexplicably resurrected character of Ian Malcolm. The book gives Carnotaurus cuttlefish-like powers of camouflage, but the dinosaurs ultimately prove no match for the tactic of annoyingly waving flashlights (really, that’s what Crichton wrote).

A pair of marauding Carnotaurus played the bad guys in Disney’s Dinosaur. But these red menaces had to suffer an anatomical redesign and wound up looking more like tyrannosaurs with horns.

By giving some of the Iguanodon a nose horn, the Mickey Mouse organization set paleontology back to the days of Gideon Mantell. The big red Carnotaurus, or “Carnotaur”, wasn’t much better.

A Carnotaurus had the starring dinosaur role in the 2008 animated movie Turok: Son of Stone. This was a film that managed to be offensive at an artistic, intellectual, and social level (kind of like Transformers 2 [Victoria's note: don't get me started on Transformers 2...]), but the Carnotaurus does get some good (though ridiculously over-the-top) action scenes.

Turok and his trusty steed prepare to go all Stone Age on a gang of Neanderthal sumo wrestlers.

Most recently, Fox TV’s Terra Nova series showed us a new CGI Carnotaurus. Terra Nova’s Carnotaurus has its flaws (though, perhaps no more so than any of its other cast members), but I enjoyed seeing it in action.

 

Outside the Terra Nova compound, a Carnotaurus squares off against what I thought was a beige version of the new Batmobile.

I would have to say my favorite media portrayal of Carnotaurus is in the absurd Japanese cartoon series Dinosaur King. In the show, a Carnotaurus named Ace is the loyal companion of a young boy and helps him fight evil.

Ace and Rex take the bus (the pet dinosaur is named “Ace” and the boy is named “Rex”).

The Dinosaur King’s CGI cartoon Carnotaurus actually suffers from fewer anatomical inaccuracies than ether Disney’s or Terra Nova’s, and it’s nice to see a theropod get to play the hero for a change. From what I’ve seen, Dinosaur King is a something of a Pokemon rip-off, and all the dinosaurs get special super powers -- some of the dinos breathe fire, others cause earthquakes, etc. And what is Ace’s special power? Super speed!

Valiantly defending us from alien invaders, mad scientist, and temporal paradoxes, Ace (seen here in his grownup form) is a two-horned, purple, people protector.