Reconstruction of Typothorax coccinarum based on skeletons from eastern New Mexico
Image by Matt Celeskey

These skeletons allowed us to revise previously published reconstructions of this aetosaur. In particular, we now have good evidence of the total number of rows of armor, the arrangement of the scutes on the belly, new insight into the appendages (particularly the shoulder girdle and feet), a more domelike carapace based on extremely wide and gently curved paramedian scutes, and the very first aetosaur reconstruction to sport cloacal spikes.

This has been a fun project to be involved with, and I thank Dr. Andy Heckert (a former coworker at the NMMNH, now at Appalachian State University) for inviting me to assist in reconstructing this armor-plated Triassic reptile.

Update 5/21: At the request of commenter dmaas, I’m uploading a detail of the head of the reconstruction. Clicking on the thumbnail will bring it up at more than twice the size of the original painting.

• Reference: Heckert, A. B., Lucas, S. G., Rinehart, L. F., Celeskey, M. D., Spielmann, J. A., and Hunt, A. P. (2010) Articulated skeletons of the aetosaur Typothorax coccinarum Cope (Archosauria: Stagonolepididae) from the Upper Triassic Bull Canyon Formation (Revueltian: Early-Mid Norian), eastern New Mexico, USA. Journal of Vertebrate Paleontology, vol. 30, no. 3, pp. 619–642.
• Elsewhere on the web:
  • Society of Vertebrate Paleontology press release (also at Appalachian State University)
  • Discovery News: Dino-Era Reptiles: Part Cow, Armadillo, Crocodile (lots of quotes from myself, the other authors & others)
  • Critical review at Chinleana: I am so disappointed in the Typothorax description in the new issue of JVP

One block, excavated by the Carnegie-led team in the 1980s, was given to the then-nascent New Mexico Museum of Natural History. In 2008, it was put on permanent exhibit. Larry Rinehart, who prepared the block for display, invited me to assist in the illustration and interpretation of some of the specimens it contained, as well as to reconstruct some of the different sizes and morphologies that were being uncovered through the analysis of dozens of specimens in this and other blocks from the quarry. The results of these investigations have been published in the past few weeks as a New Mexico Museum of Natural History and Science Bulletin (Rinehart et al. 2009).

In future posts, I hope to showcase some of the specimens, interpretations, and conclusions we came to as a result of these investigations. Note that everything I post here will be based on my own understanding and interpretation of the work, much of which was performed by the other authors. I don’t intend to misrepresent any of the procedures or findings, but if it happens, errors in reporting should be considered mine alone.

With that caveat in mind, I’d like to introduce the main object of the study: the NMMNH Coelophysis block.

The NMMNH Coelophysis block (Quarry # C-8-82) after preparation

The NMMNH block is a two ton wedge of reddish Chinle siltstone, trimmed down considerably from the original 12,000 pounds pulled out of the quarry in 1982. Across its exposed surface lie more than two dozen specimens referrable to Coelophysis bauri, plus a couple non-dinosaur bits & pieces. Several jackets removed from the block contain many more fossils of Coelophysis, along with an impressive sampling of Triassic fish and reptiles.

Schematic drawing of selected Coelophysis specimens on the exposed surface of the NMMNH block

Up from the Bottom
or, Lessons from a Triassic Turnover.

When looking at the prepared surface of the NMMNH block, everything you see is upside down—the block was flipped over and prepared from the bottom up. This was done to facilitate access to the primary bone layer by avoiding the reworked, poorer-quality bones found above this layer in other blocks. It also revealed new information about the environment where the Coelophysis were buried. Beneath the main Coelophysis beds were found layers containing rip-up clasts running in the same direction as most of the Coelophysis bones—evidence of rushing water that tore up chunks of the underlying mud as it swept the dinosaur bodies in.

A previous study of the taphonomy of the quarry (Schwartz & Gillette 1994) also concluded that water transported the Coelophysis to their burial site. Based on several lines of evidence, Schwartz and Gillette proposed that the animals died during a prolonged drought and were subsequently washed downstream by a flood, where their carcasses clogged a narrow channel prior to burial. But some tiny fossils near the bottom of the NMMNH block suggested a slightly different scenario to us.

Beneath the rip-ups were the fossils of tiny invertebrates—conchostracans and ostracods—often found in temporary bodies of water. They led us to consider that the quarry was once the site of an ephemeral pond—a topographic depression where water might collect during a wet season, followed by dry periods where the water would disappear. An unfortunate flock of Coelophysis, swept up in the flooding of a nearby river, might have been washed into this low spot in the landscape and buried.

The death/burial poses of the seven most complete Coelophysis specimens on the NMMNH block

As for the cause of death, there seemed little reason to suspect any agent beyond the flood that buried them. In fact, one observation previously cited as evidence for post mortem desiccation—the opisthotonic posture where neck and tail are flexed sharply upward and curled over the back—now seems more likely to indicate the death throes of animals suffering the final effects of disease, poison, or (in this case) lack of oxygen due to burial or drowning (Faux & Padian, 2007).

If the bonebed at the Whitaker/Coelophysis quarry is the end result of a single catastrophe, then it preserves an excellent sampling of a population of early dinosaurs. It may possibly be the largest (in terms of numbers of individuals) Mesozoic dinosaur population we know of. This provides an unparalleled opportunity to study growth and variation within a single dinosaur species. Before getting to that, however, I’d like to spend a post reviewing some of the other, non-Coelophysis fossils found within this and other quarry blocks.

Next time: It’s your Lagerstätte, I’m just buried in it
or, Token Diversity in a Dinosaur Graveyard.

• Main Reference: Rinehart, Larry F., Lucas, Spencer G., Heckert, Andrew B., Spielmann, Justin A. and Celeskey, Matthew D., 2009. The Paleobiology of Coelophysis bauri (Cope) from the Upper Triassic (Apachean) Whitaker quarry, New Mexico, with detailed analysis of a single quarry block. New Mexico Museum of Natural History and Science Bulletin 45, 260pp. Abstract [Rich text file]
• Additional References: Faux, Cynthia M. and Padian, Kevin, 2007. The opisthotonic posture of vertebrate skeletons: postmortem contraction or death throes? Paleobiology, vol. 33 (2), pp. 201–226. doi: 0.1666/06015.1
• Heckert, Andrew B., Lucas, Spencer G., Rinehart, Larry F. and Hunt, Adrian P., 2008. A new genus and species of sphenodontian from the Ghost Ranch Coelophysis quarry (Upper Triassic: Apachean), Rock Point Formation, New Mexico, USA. Palaeontology, vol. 51, pp. 827–845. doi: 10.1111/j.1475-4983.2008.00786.x [PDF]
• Nesbitt, Sterling J. and Norell, Mark A., 2006. Extreme convergence in the body plans of an early suchian (Archosauria) and ornithomimid dinosaurs (Theropoda). Proceedings of the Royal Society B, vol. 273, no. 1590, pp. 1045–1048. doi: 10.1098/rspb.2005.3426
• Nesbitt, Sterling J., Stocker, Michelle R., Small, Brian J. and Downs, Alex, 2009. The osteology and relationships of Vancleavea campi Zoological Journal of the Linnean Society, vol. 157 (4), pp. 814–864. doi: 0.1111/j.1096-3642.2009.00530.x
• Schwartz, Hilde L. and Gillette, David D., 1994. Geology and Taphonomy of the Coelophysis Quarry, Upper Triassic Chinle Formation, Ghost Ranch, New Mexico. Journal of Paleontology, vol. 68 (5), pp. 1118–1130.

The NMMNHS has a fantastic collection of natural history art commissioned specifically for its exhibits. Highlights on the tour will include Margaret Colbert’s Dawn of the Dinosaurs paintings (detail shown above), Dave Thomas’ life-size bronze dinosaurs, Spike and Alberta, Ely Kish’s Jurassic murals, mosasaur and dinosaur sculptures by Stephen Czerkas, plus works by Karen Carr, Gary Staab, and many others. We’ll take a look at some of the science behind the art, techniques that were used to create the pieces, and how our views of the past have changed since some of these works were completed.

The whole shebang costs $7 ($3 for museum members) and is limited to 20 participants. I’m told that there are a few spaces left. If you would like to join in, you can either download a registration form or simply email programs.NMMNHS[at]state.nm.us to reserve a space.

I’ll write up more about my contribution to this in the next couple of days, but for now, I’ll repost the abstract below:

We statistically extracted size (= age) classes from Coelophysis bauri metrics. Using these size classes, we generated a hypothetical growth curve for C. bauri based on femur lengths (N=56). This curve is similar in shape to that of some birds (e.g. Gallus gallus) with the differences largely in time scale, and also to previously reported histologically derived growth data for C. kayentakatae rhodesiensis. Age and mass distributions were then calculated based on the number of individuals in each age class and on femur dimensions. Hypothetically, Coelophysis’ growth rate was very high for the first year. Sexual dimorphism apparently onset between years one and two. After one year growth slowed in the gracile morph while the robust morph is first apparent and grew aggressively for another year; slow growth then continued in both morphs. Robust and gracile morphs probably represent males and females respectively based on their sexual dimorphism index (SDI = robust size / gracile size = 1.34). Both age and mass distributions are of hyperbolic form. Very small ~one-year-olds weighing ~2 kg and ~1.4 m long comprise 40 % of the population, ~11 % are adults weighing ~14 kg and ~2.7 m long, ~2 % reach 25 kg and 3.1 m length.

Our allometry study, based on the 15 suitably complete specimens, agrees with previous studies showing that orbits and hind limbs show negative allometry while skull and neck lengths are positive. Allometric growth constants (this study) relative to total length are: skull length, 1.62; cervical series, 1.31; sacrum, 1.26; caudal series, 0.78; forelimb inc. hand, 1.3; hand, 1.52; hindlimb inc. foot, 0.92; foot, 0.91. Relative to skull length: orbit diameter, 0.28; height at quadrate, 0.22; height at prefrontal, 0.32. The cervical series shows complex allometry (log-transformed data are better fit by a polynomial than linear regression); growth rate being high in juveniles and progressively lower in adults. Thus, relative to adult proportions, juveniles had very short, high faces with large orbits, very short necks, short torsos, long tails, short arms, very small hands, long legs and large feet.

Larry and my other coauthors have agreed to make available for download a PDF of the 2-page, 11 x 17″ handout for any interested parties:

Rinehart_etal_svp2008handout.pdf [1.4Mb PDF]

• Reference: Rinehart, L. F., Heckert, A. B., Lucas, S. G., and Celeskey, M. D., 2008. Growth, allometry, and age/size distribution of the Late Triassic theropod Coelophysis bauri: preliminary results. Journal of Vertebrate Paleontology Vol. 28, suppl. to No. 3.

This was the scene at The Day Job a couple of weeks back, as we unpacked a sculpture for the newly-opened Triassic exhibit. I happened to be wearing the right shirt for the occasion, and my boss David snapped this picture. The piece I’m holding is a fantastic restoration of the freshwater coelacanth, Chinlea sorenseni, about to snap up a school of Synorichthyes. The fish were sculpted by the talented Gary Staab of Staab Studios for the exhibit.

And here’s how the sculpture looks on display, beneath a cast of an fossil Chinlea skull and some Triassic coelacanth bits from New Mexico. The panel is sandwiched between a petrified lungfish burrow and the reconstructed leaves of the enigmatic plant Sanmiguelia. A reflection from the fishtank of Kirby, a living African lungfish, can be seen in the window:

I’ll be at the museum for an exhibit poster signing from 9:00 to noon, so if you’re in the vicinity, stop by and say hi.

If you aren’t anywhere near Albuquerque, there’s still a portion of the exhibit tailor-made for you. There hasn’t been any press on this yet, but if you swing by nmstatefossil.org and poke around, you’ll find a wealth of information on New Mexico’s most famous fossil resident, the little dinosaur Coelophysis. The NMMNHS has gotten permission from several authors, publishers, and other museums to distribute much of the primary literature on this Triassic theropod, so digging deep into the site will allow you to access a couple dozen PDFs of technical and popular articles.

The site was put together by Ideum, a fantastic group of interactive developers in Corrales, NM. They also worked with us on an in-hall interactive to interpret our two-ton Coelophysis block from Ghost Ranch:

The touchscreen display features a drag-and-zoom viewer that allows visitors to get a detailed look at the block, a series of highlighted features that can be toggled on and off, video segments of the block’s preparator explaining the features in detail, and an overlay showing the death positions of 7 of the more complete Coelophysis preserved in the block. More info about the interactives can be seen at Ideum’s blog and portfolio site.

And some quick pictures from before I dash out the door:

The skulls of Triassic amphibians. Clockwise from the top: Eocyclotosaurus (cast), Hadrokkosaurus (cast), juvenile and adult Buettneria (fossil), and Mastodonsaurus (cast).

A touchable bonded-bronze cast of the aetosaur Typothorax coccinarum.

Phytosaur skulls (Pseudopalatus buceros) from the Snyder Quarry near Ghost Ranch.

The tiny braincase of the earliest-known mammal, Adelobasileus cromptoni.

The post includes a couple of illustrations done for the hall: a rendering of the early mammal Adelobasileus by illustrator Mary Sundstrom, and my own painting of a large archosauriform known from a few dozen well-weathered fossils from the Middle Triassic of New Mexico. The restoration (shown above) is based largely on big erythrosuchian predators like Erythrosuchus and Shansisuchus (from South Africa and China, respectively).

This is the project I’ve been looking forward to working on since I started at the museum almost a decade ago, and finally all the pieces have come together to pull it off.  Everyone involved in the exhibit is itching to show off some the fantastic Triassic fossils from the museum collections. The article only hits some of the highlights: this photo shows a beautifully preserved young Coelophysis from the Museum’s Ghost Ranch block (read the article for more Coelophysis-as-cannibal news). Another picture shows a the beginnings of a life-sized model of a New Mexican erythrosuchian, while the final position of one of the big stars remains tastefully hidden until the opening.

I’m not certain how much I’ll be able to share here until the exhibit opens, but I’ll definitely pass along any info that’s been made public before then.

The upside is that I’m making more time during the normal workdays to paint. The downside is that I’m squeezing it in alongside several other duties that are coalescing around the same exhibit. Actually, that isn’t really a downside, since everything I’m working on is pretty exciting—the real downside is that it will be bleeding into more personal time as the holidays approach. Postings here may tend to be a bit sporadic over the next few weeks as a result.

In anticipation of this, I’ve bitten the bullet and ordered a long-overdue replacement to my aging computer. I’m hoping it will help me accomplish the tasks ahead at blazing speed, but I’m sure its main function will be to serve as a shiny bit of positive reinforcement when I need to hunker down and plug away at some image files or layouts.

Speaking of layouts, I’ve been threatening to redesign this site for a couple of months now, so I really should add that to the list of things that need my attention this month. When I last mentioned it, a couple of comments encouraged me to retire the Titanophoneus skull that has grinned out from the HMNH logo for the past three years, in favor of something a little more appropriately hairy. I haven’t quite settled on what will replace it just yet, but there are a couple of fruitful possibilities…

…so, just off the cuff, is there a kind reader out there able to send me a PDF of the following article?

Hopson & Kitching 2001. A probainognathian cynodont from South Africa and the phylogeny of non-mammalian cynodonts. Bulletin of the Museum of Comparative Zoology, 156, p.5-35.

Still, I’ve got a good handful of concept drawings, preliminary studies, and works in progress that should provide a sneak peek at some of the exciting goings-on in the Exhibits Department at the New Mexico Museum of Natural History and Science. The New Mexico Friends of Paleo. meetings are free and open to the public, so if there are any interested readers in the Albuquerque area, feel free to pop in on Monday!