Hairy Museum of Natural History

For any New Mexico readers, there are a couple of lectures coming up this week that would be of interest to the paleontology-minded:

The NM Friends of Paleontology are meeting Monday, Nov. 17 at 7:00pm at the New Mexico Museum of Natural History and Science. This month’s meeting includes a talk by Larry Rinehart on some of the recent work he’s done on the allometry, growth, dimorphism and population structure of Coelophysis bauri from Ghost Ranch. The NMFOP meetings are free and open to the public.

On Thursday the 20th, geologist David Love and paleontologist Gary Morgan will be giving a talk on a 10 million year old oreodont recently unearthed at the Bosque del Apache Wildlife Refuge. The talk will begin at 3:30pm in the Macey Center auditorium at New Mexico Tech in Socorro (admission $5). More info about this find is online here.

—Matt Celeskey.

File under: Dinosaurs, Mammals, Neogene, Recent Discoveries, Triassic.

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Striving for fair and balanced reporting for all arthropod aficionados:

A few weeks old, but worth noting: World’s oldest flying insect fossil. A beautiful resting trace from a Carboniferous insect that landed with its limbs sprawled out like a mayfly; found in Massachusetts by a geology student at Tufts University.

Moving back in time, Chris Nedin kicks off his new Ediacaran blog with a compelling Cambrian tale of how flexible trilobites avoided unlucky breaks in The Spandrels of San Marco and the Anomalocaris Paradigm.

Speaking of the Cambrian, scientists are furthering their insight into the exceptional preservation of the famous Burgess Shale fossils, according to this article.

And  The Life of Madygen provides a brief introduction to the Triassic titanopterans, an extinct group of insects, related to grasshoppers and crickets, but with wingspans reaching half-a-meter across!

—Matt Celeskey.

File under: Cambrian, Carboniferous, Invertebrates, Triassic.

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As previously mentioned, today our poster on the growth, allometry, and age/size distribution of Coelophysis bauri goes up at SVP.

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.

—Matt Celeskey.

File under: Dinosaurs, The Day Job, Triassic.

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As long as I’ve got some posts lined up about the Coelophysis population from the Whitaker Quarry at Ghost Ranch, it only seems appropriate to work in this little bit of month-old news: a new sphenodontian, a small, superficially lizard-like reptile related to the tuatara, known from some partial jaws found in a block from the Whitaker Quarry:

• 
• Whitakersaurus bermani
  Drawing by me, from the day job.

• New Sphenodontian: Whitakersaurus bermani
• Name Means: Berman’s Whitaker lizard.
  (George Whitaker discovered the Coelophysis Quarry where this fossil was found, and David Berman’s fieldwork led to the recovery of the block that contained the type specimen.)
• Relations: Sphenodontian rhynchocephalian
• Location: New Mexico, U.S.A.
• Age: Late Triassic, ~203,000,000 years ago
• Reference: Heckert, A. B., Lucas, S. G., Rinehart, L. F., & Hunt, A. 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 51 (4): 827-845.
• Web coverage:
  • Chinleana: Latest Literature: August 2008.
  • Santa Fe New Mexican: New Species Emerges from Fossil

—Matt Celeskey.

File under: Reptiles, Triassic.

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The catastrophic death assemblage preserved at the Ghost Ranch, New Mexico Coelophysis (Whitaker) Quarry provides a unique opportunity to illustrate a population of Late Triassic theropod dinosaurs. Measurements of 56 individuals at the Quarry suggest a population quite different from those shown in typical illustrations of the “Ghost Ranch Flock.”

Right about now the above text and image should be going up at the PaleoArt Poster Exhibit running alongside the Opening Reception for the SVP Annual Meeting.

Over the past year, I’ve worked with Larry Rinehart to develop skeletal reconstructions of Coelophysis at different growth stages, based on his statistical and allometric studies of the fossils preserved in blocks from the Ghost Ranch Quarry. The preliminary results of that study, and the skeletal reconstructions we’ve developed so far, will be presented during the poster session this Saturday. (For interested readers who aren’t at the conference, check back here when the embargo lifts on Saturday evening for more details.)

One interesting facet that came out of this study was the “demographics” of the Ghost Ranch population—over 40% of the preserved specimens came from small juveniles less than 2kg in weight (like those shown above). Large adults (like AMNH 7223 and 7224, the specimens that most depictions of Coelophysis are probably based on) make up less than 10% of the known specimens of C. bauri. This fits pretty well with the population dynamics of modern crocodiles, and it has some rather dynamic visual implications for artists restoring scenes showing large groups of Coelophysis. I wanted to come up with a quick study portraying this new interpretation of the “Ghost Ranch Flock”

If a population consists of many more children than adults, its a cinch that relatively few Coelophysis hatchlings made it to adulthood. While the case for cannibalism in Coelophysis is still contested, I figured that throwing in an adult grabbing a meal to go in the background would underscore the potential difficulties faced by C. bauri youth. This, along with many other details in the picture, is based on evidence from the NMMNH Coelophysis block—in this instance, some very coelophysoid-looking bones in the coprolites and cololites found aside/inside the skeletons of adults in the block.

—Matt Celeskey.

File under: Dinosaurs, Triassic.

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