Field of Science

Success in Bristol

Despite running concurrent to the best student presentations (Romer Prize), the Preparators and Bird/Dinosaur sessions, the Triassic symposium managed to draw large crowds for each talk. In fact I heard we had better crowds than the bird/dinosaur talks. This would have simply been unheard of six or more years ago and is a testament to all the great research going on in Triassic paleontology right now.

I am no longer in Bristol, and instead am sitting in a pub in central London downing a pint of bitter and watching football (soccer) on the telly. This years SVP meeting was excellent and held in a great place with 1100 great colleagues. Tomorrow Jeff and I are off to the Natural History Museum to look at the holotype of Stagonolepis robertsoni.

The 69th Annual Meeting of the Society of Vertebrate Paleontology



This week I will be attending the annual meeting of the Society of Vertebrate Paleontology. Jeff Martz and I have been invited to present a paper on our recent biostratigraphic work in the Petrified Forest as part of a special symposium "Late Triassic Terrestrial Biotas and the Rise of Dinosaurs". This year the meeting is being held in Bristol, England and as I have never been to the U.K. (or Europe) before this should be a real treat. I will be following up the meeting with a few days of research at the Natural History Museum in London. I must remember to look the opposite way before crossing streets or this will be a very short trip!


Cynodonts and More Cynodonts

The current issue of the Journal of Vertebrate Paleontology has two articles on Gondwanan cynodonts that are important for Middle Triassic biostratigraphy.

Abdala, F., and R.M.H. Smith. 2009. A Middle Triassic Cynodont Fauna from Namibia and Its Implications for the Biogeography of Gondwana. Journal of Vertebrate Paleontology 29:837-851. doi: 10.1671/039.029.0303

Abstract - The upper Omingonde Formation of Namibia contains a diverse vertebrate fauna represented by amphibians, dicynodonts, archosaurs, therocephalians, and cynodonts, which is generally considered to be of Anisian age. Four cynodont taxa (Cynognathus, Diademodon, Trirachodon, and Titanogomphodon) are currently known from this fauna. Here we document four additional cynodonts, all of which were recovered from the highest levels of the formation: Luangwa, an indeterminate traversodontid, Aleodon, and Chiniquodon. These discoveries allow us to recognize the Omingonde Formation as preserving the most diverse fauna of Middle Triassic cynodonts in the world. Furthermore, we recognize that the formation is a biostratigraphic link among Middle Triassic faunas from South Africa, Tanzania, Zambia, Argentina, Brazil, and Antarctica. Aleodon is recorded here for the first time in Anisian faunas of southern Africa, and the unexpected record of Chiniquodon poses a biostratigraphic enigma because this taxon is known only from Ladinian—Carnian faunas of South America. We explore some possible scenarios related to the radiation of traversodontid cynodonts in Gondwana during the Anisian.

Martinelli, A.G., de la Fuente, M., and F. Abdala. 2009. Diademodon tetragonus Seeley, 1894 (Therapsida: Cynodontia) in the Triassic of South America and Its Biostratigraphic Implications. Journal of Vertebrate Paleontology 29:852-862. doi: 10.1671/039.029.0315

Abstract - We report for the first time the presence of the cynodont Diademodon tetragonus Seeley, 1894 in the South American Triassic. The specimen, represented by a fragmented skull and lower jaws, was found in levels of the Rio Seco de la Quebrada Formation (Puesto Viejo Group), Mendoza Province, Argentina. It is assigned to D. tetragonus based on its overall skull shape (narrow and elongated snout with a concave outline in dorsal view), the morphology of the jugal that forms most of the dorsoventral depth of the zygoma and shows a well-excavated external auditory meatus, and a postcanine series including circular outlined anterior teeth, ovoid gomphodont teeth in the middle, and posterior sectorial teeth. The association of this taxon with the cynodonts Cynognathus crateronotus and Pascualgnathus polanskii, along with comparisons to African Triassic assemblages, suggest an Early to Late Anisian age for the Río Seco de la Quebrada Formation. These levels are most likely correlated to the subzones B and C of the South African Cynognathus Assemblage Zone, where both Cynognathus and Diademodon are known. This discovery represents the fourth report of shared cynodont genera between allegedly Lower to Middle Triassic African and South American terrestrial faunas.

Cute! Raptorex kriegsteini New Miniature Tyrannosaur from the Early Cretaceous of China

This isn't Triassic, but it has been a slow month and this is pretty cool. Out today in Science is an article describing a new miniature tyrannosaur from the Early Cretaceous of China. Sereno et al. have named the specimen Raptorex kriegsteini after the parents of the benefactor who purchased the specimen from a private seller at the Tucson Gem and Mineral Show. This is a good story about how an illegally collected specimen is donated by a benefactor to science, studied and published for the scientific community and the public, and now will be returned back to China from where it was removed.


You can read more on this find here:

http://www.chicagotribune.com/news/chi-090917little-t-rex,0,2156860.story

http://www.sciencenews.org/view/generic/id/47453/description/Tiny_T.rex%E2%258

http://scienceblogs.com/notrocketscience/2009/09/raptorex_tiny_king_of_thieves_shows_how_tyrannosaurus_body_p.php

The reconstruction is from here. Todd Marshall does amazing work.

One thing I did notice is that the species name is improperly constructed. Because the specimen is named for Mr. and Mrs. Kriegstein, by ICZN convention the name should be R. kriegsteinorum. This seems to occur more often then it should, especially with multiple authors, reviewers, and editors.

REFERENCE

Sereno, P.C., Tan, L., Brusatte, S., Kriegstein, H.J., Zhao, X., and K. Cloward. 2009. Tyrannosaurid body design first evolved at small body size. Science 325. doi: 10.1126/science.1177428

Supplemental Material

Did Tetrapods Undergo a Postural Shift after the End-Permian Extinction?

Kubo, T. and M. J. Benton. 2009. Tetrapod postural shift estimated from Permian and Triassic trackways. Palaeontology 52:1029-1037. doi: 10.1111/j.1475-4983.2009.00897.x

Abstract- The end-Permian mass extinction, 252 million years (myr) ago, marks a major shift in the posture of tetrapods. Before the mass extinction, terrestrial tetrapods were sprawlers, walking with their limbs extended to the sides; after the event, most large tetrapods had adopted an erect posture with their limbs tucked under the body. This shift had been suspected from the study of skeletal fossils, but had been documented as a long process that occupied some 15–20 myr of the Triassic. This study reads posture directly from fossil tracks, using a clear criterion for sprawling vs erect posture. The track record is richer than the skeletal record, especially for the Early and Middle Triassic intervals, the critical 20 myr during which period the postural shift occurred. The shift to erect posture was completed within the 6 myr of the Early Triassic and affected both lineages of medium to large tetrapods of the time, the diapsids and synapsids.

Enigmatic Triassic Taxa - Kraterokheirodon colberti

When you watch 'Walking With Dinosaurs' the Triassic portion (which supposedly represents the Chinle Formation of Arizona) contains numerous scenes featuring a group of cynodonts. In reality this presence of cynodont therapsids in the Chinle Formation was based on two teeth. The first (AMNH 4947) was found at St. Johns Arizona in 1946 by Guy Hazen of the USGS and presented to Ned Colbert that summer and reposited at the American Museum of Natural History. The second tooth (PEFO 9984) was found in 1984 on a geology field trip through Petrified Forest National Park. Preliminarily assigned to traversodont cynodonts (e.g., Long and Murry, 1995) these teeth were under study by Colbert until his passing in 2001.

The location of these specimens was unknown until 2002 when Randall Irmis was helping sort out Colbert's office at the Museum of Northern Arizona and found the original and a cast of PEFO 9984 and a cast of AMNH 4947 (unfortunately the original specimen has yet to be rediscovered).

In 2005 Randy and I published a paper describing these teeth as a new taxon, Kraterokheirodon colberti. The name, created by Randy, means "cupped hand tooth", which describes the morphology of the occlusal surfaces (cusps) of the teeth (six in all), and also honors Ned Colbert. [photo below is of PEFO 9984 in what we believe is a posterior view, the crown is to the left].


The morphology of these teeth is unique "differing from all other known vertebrate teeth in possessing a convexly arched transverse ridge of six cusps." The problem is that they are so unique that determining a taxonomic assignment for this taxon is almost impossible at this time. The thecodont implantation suggests tetrapod affinities, but assignment to a less inclusive clade is ambiguous. [photo below is of PEFO 9984 in occusal view].




One thing is clear, these teeth belong to a very large tetrapod with a long stratigraphic range. The AMNH tooth is from the Monitor Butte Member near the base of the Chinle, whereas the PEFO tooth is from the middle of the Petrified Forest Member. What is even more of a mystery is how such a large animal could escape detection in the well known Chinle faunal assemblage. The largest tetrapods found in these assemblages are phytosaurs and rauisuchians, two groups in which the dentition is very well known and extremely different than that of Kraterokheirodon.

Even though Revueltosaurus was only known from teeth for over 15 years, this was simply due to not finding teeth directly associated with other bones as non-dental material had been collected as early as the 1920s. To date, my colleagues and I have no candidate specimens to associate with the teeth of Kraterokheirodon. No potential postcrania, zip. As with Acallosuchus rectori, our only hope is to keep sampling the horizons in which these teeth occur in hopes of finally solving the mystery as we did with Revueltosaurus (Parker et al., 2005).

REFERENCES

Irmis, R. B., and W. G. Parker. 2005. Unusual tetrapod teeth from the Upper Triassic
Chinle Formation, Arizona, USA. Canadian Journal of Earth Science 42: 1339–1345.
doi: 10.1139/E05-031

Long, R. A., and P. A. Murry. 1995. Late Triassic (Carnian and Norian) tetrapods from the southwestern United States. New Mexico Museum of Natural History and Science Bulletin 4:1-254.

Parker, W.G., Irmis, R.B., Nesbitt, S.J., Martz, J.W., and L.S. Browne. 2005. The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. Proceedings of the Royal Society B 272:963-969. doi:10.1098/rspb.2004.3047

These Guys Might Be Crazy

...or maybe not.... or maybe so.

Nonetheless I've got to give Matt Wedel, Mike Taylor, and Andy Farke kudos for a very interesting, definitely novel, and potentially insane idea. They appear to be looking for (apparently thousands of) potential co-authors in a new project to build a large database of measurements for ornithischian dinosaur bones to attempt to solve a variety of research questions. This database will be open access and available to all researchers providing measurement data for potentially every known ornithischian dinosaur bone. Amazing...or maybe foolish. Is this a pipe dream or absolute brilliance that will revolutionize the field of vertebrate paleontology? It's too early to say and the only way to find out for sure is to get involved. Too bad there aren't any Triassic ornithischians in North America, guess I'm out ;).

You can read all about this and get started here, here, here, and read some commentary here.

Discovery of an Entire Fossil Cycad from the Late Triassic of China

One of the frustrating things about fossil plants is that when the die they tend to break down rapidly and fall apart. Thus finding an entire plant is rare and therefore the leaves, stems, and reproductive structures are often found separately and provided different taxonomic names. Even at Petrified Forest National Park we do not know for certain what foliage belongs with our main types of fossil wood, although we do have isolated preserved foliage. A recent article in Chinese Science Bulletin (Springer) documents an entire cycad from the Late Triassic of China. This well preserved specimen includes the leaves, pinnae, stem, and a male cone as well as preserving their arrangement. An amazing and important find, unfortunately the article is just a note and not a full description and discussion. According to the article this is forthcoming.

You can download the PDF here for free until the end of November 2009 courtesy of Springer. The image above is from the article.

Wang, X., Li., N., Wang, Y. D., and S. Zheng. 2009. The discovery of whole-plant fossil cycad from the Upper Triassic in western Liaoning and its significance.
Chinese Science Bulletin 54: 3116―3119. doi: 10.1007/s11434-009-0384-z

Abstract - A recently discovered megafossil of whole plant cycad is briefly reported here. The specimen is collected from the Yangcaogou Formation (Upper Triassic) in Changheying, Beipiao, Liaoning. The whole plant is preserved intact on a sandstone slab, 89 cm long and 130 cm wide, including leaves up to 82 cm long and a male cone physically attached to the stem apex. Analysis on the morphology, arrangement and venation of leaf and pinna, male cone and its relationship with other parts indicates that the fossil is closely related to living Zamiaceae in Cycadales. This cycad fossil is hitherto most completely preserved cycad specimen including both vegetative and reproductive organs. Its discovery contributes much to our understanding of the morphology and evolution of cycads, palaeoclimate as well as palaeoenvironment.

Thanks to Randy Irmis for sending this on.

Investigating the Non-Marine TR/J Boundary in Portugal

Dr. Richard Butler (Bayerische Staatssammlung für Paläontologie und Geologie, Munich), Dr. Octavio Mateus (University of Lisbon) and Steven Brusatte (American Museum of Natural History) have initiated a new field project to study terrestrial strata (Grès de Silves Formation) spanning the Triassic-Jurassic boundary in Portugal in hopes of recovering late surviving temnospondyls and possibly other Late Triassic vertebrates. Preliminary results are encouraging and you can read about them here.


Given that many Late Triassic Laurasian faunal assemblages appear very similar in content despite their stratigraphic position (e.g., Placerias Quarry vs. Coelophysis Quarry in the Chinle Formation), these types of studies are crucial to our understanding of exactly what is happening with the Triassic-Jurassic non-marine extinctions. Unfortunately many places that preserve this boundary and are accessible are non-fossiliferous (e.g., Newark Supergroup); whereas other places that may be very fossiliferous (e.g., Moenave and Kayenta Formations of Arizona) are not easily accessible.

"Moon Rock" is Petrified Wood

This story was all of the news a couple of days ago. A piece of rock purportedly collected from the moon by Apollo 11 and given to a dutch museum of a United States envoy back in 1969 is actually a piece of petrified wood.




You can read more about this here, here, and here.

These articles were pointed out on the Vertebrate Paleontology list server and the following reply was posted by Triassic paleobotanist Sid Ash. As Sid is a friend and reader I hope he does not mind me reposting his comments here.

"As a paleobotanist who has studied petrified wood for many years I would identify the specimen as almost certainly a piece of Upper Triassic "Rainbow Wood" which occurs in great abundance in Petrified Forest National Park and adjoining areas in the southwestern United States. Most other petrified wood ranges from shades of brown to black and is not as distinctive as Rainbow Wood which is usually dark red in color. See references for more information on Rainbow Wood.

---Sidney Ash"

As there is an extremely good chance that this piece of wood is from the Chinle Formation and possibly Petrified Forest National Park, I admit I must take slight offence at the following comment from the article:

""It's a nondescript, pretty-much-worthless stone," Geologist Frank Beunk concluded in an article published by the museum."

And this is amusing as well:

"He said the rock, which the museum at one point insured for more than half a million dollars, was worth no more than euro50 ($70)."

That seems about right for that size of a piece; however, if it could be demonstrated that the rock was taken illegally from the Petrified Forest the fine is over $300.

REFERENCES

Ash, S. R. 2005. Petrified Forest: A story in stone. Petrified Forest Museum Association, Petrified Forest, AZ. 48 p.

Ash, S. R. 2007 Petrified Forests. In: McGraw-Hill Encyclopedia of Sciences & Technology, 10th Edition. Vol.13, p. 230-234.