Thursday, February 23, 2012

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!

Tuesday, February 21, 2012

Cool Stuff


"Cool Stuff: The University of Alberta Museums Do Winter" is a winter-themed exhibit that opened last week at the U of A's Enterprise Square location. I checked it out last weekend and was pleased to see so many different types of objects on display. We have 28 different collections on campus, and most (maybe all?) were represented in the exhibit - butterflies, moss, picked parasites, textiles, and more. 


The University of Alberta Laboratory for Vertebrate Paleontology contributed fossils from our Grande Prairie and Edmonton dinosaur bonebed excavations. Although we usually collect stuff in the summer, we've had snow during our Edmonton fieldwork, even in May.


We showed off some field jackets, too. The Monoclonius and ornithomimid are pretty self-explanatory, and if I recall correctly, "Skull B" is from the Wapiti bonebed in Grande Prairie. There were also photos from our December tyrannosaur helicopter lift in Dinosaur Provincial Park, including a photo taken by me!


Last spring we purchased a cast of the Cryolophosaurus original non-reconstructed skull for both teaching and research, but it fit in perfectly with the exhibition theme! The grey slab behind the skull is the Wonder Block from the MOTH locality, which has a variety of 'jawless fish'. Phil will be giving a talk about his 2011 Antarctic expedition on March 1, as part of the exhibition's speaker series.


The exhibition also features specimens from our zoology collections, including these Arctic and sub-Arctic mammals (caribou, deer, and walrus).


"Cool Stuff" mixes natural history objects with cultural heritage objects, and in particular I was pleased to see so many Inuit and Inuvaliut art pieces. I am always astounded by whalebone sculptures like this one.


Another display had Inuit dolls, musical instruments, hunting tools, and boots. The beautiful paintings in the background are the original art from Ted Harrison's "A Northern Alphabet". Click the photo to make it bigger, and see if you can figure out what letter each painting represents.

"Cool Stuff" is open until March 4, and admission is free. It was cool, go check it out. 

Monday, February 20, 2012

Spared no expense.


Well, this weekend marked a major milestone for me: I saw Jurassic Park on the big screen for the very first time! Although I have watched it countless times, first on VHS and then on DVD, Victoria in 1993 was only 9 years old, squeamish, and easily scared by, well, scary stuff, and thus too small to see Jurassic Park during its initial theatrical release. 


The film was being shown as part of Alberta Innovates - Health Solutions film series called Science in the Cinema. They feature films with a biomedical slant, and ask health science and biomedical researchers to do a Q & A after the film. In Edmonton, the movies are shown at a cool old theatre called the Garneau Theatre, and admission is free (with free popcorn, too!).


For Jurassic Park, they also asked if some students from my lab could come out to talk about dinosaurs, and so Scott and I brought along some fossils to show off before and after the movie. We are lucky to have casts of many of the dinosaurs featured in Jurassic Park, so we brought along casts of Gallimimus, Tyrannosaurus, and of course, Velociraptor. We also brought along some sturdy, real, touchable Edmontosaurus fossils from a bonebed in Edmonton, which were also a big hit.


There were a lot of good questions about both the genetics and palaeontology sides of Jurassic Park, and apparently there were about 450 people in the audience. It was fun to see good ol' Jurassic Park with an enthusiastic crowd of people who obviously knew the film well, and lots of younger kids who were seeing it for the first time. It has held up surprisingly well, and I maintain that the computer animation in Jurassic Park, which was the first time that realistic living creatures were created using that technique, is still some of the best computer animation ever. Yes, there are some inaccuracies, and yes, the theropods should be feathered, but overall for a film that is now 19 years old, it's not too shabby. ("Cool, it's an interactive CD-ROM!" and "It's a UNIX system! I KNOW this!" both got some pretty big laughs.)

Tuesday, February 7, 2012

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 100th 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:


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.

Monday, February 6, 2012

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:

Friday, February 3, 2012

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.