Field of Science

Latest Literature

A few new papers which recently came to my attention and that deal (at least somewhat) with Triassic vertebrates....


Allain, R., and E. Lang. In Press. Origine et evolution des saurischiens (Saurischian origins and evolution). Compte Rendus Palevol. doi:10.1016/j.crpv.2008.09.013

Abstract: We propose here a short synthesis of the saurischian evolutionary history. Our knowledge of the diversity and evolution of the saurischian non-avian dinosaurs has increased during the past decade. The generalized use of cladistics has led to various phylogenetic hypotheses, some of them in agreement on the evolution of saurischians, even if some controversy remains. The saurischian evolution is closely linked to two of the five great mass extinctions, which punctuated life history, but probably also to a third, less important, extinction event at the end of the Early Jurassic.

Dyke, G. J., McGowan, A.J., Nudds, R.L., and D. Smith. In Press. The shape of pterosaur evolution: evidence from the fossil record. Journal of Evolutionary Biology. doi:10.1111/j.1420-9101.2008.01682.x

Abstract: Although pterosaurs are a well-known lineage of Mesozoic flying reptiles, their fossil record and evolutionary dynamics have never been adequately quantified. On the basis of a comprehensive data set of fossil occurrences correlated with taxon-specific limb measurements, we show that the geological ages of pterosaur specimens closely approximate hypothesized patterns of phylogenetic divergence. Although the fossil record has expanded greatly in recent years, collectorship still approximates a sigmoid curve over time as many more specimens (and thus taxa) still remain undiscovered, yet our data suggest that the pterosaur fossil record is unbiased by sites of exceptional preservation (lagerstatte). This is because as new species are discovered the number of known formations and sites yielding pterosaur fossils has also increased – this would not be expected if the bulk of the record came from just a few exceptional faunas. Pterosaur morphological diversification is, however, strongly age biased: rarefaction analysis shows that peaks of diversity occur in the Late Jurassic and Early Cretaceous correlated with periods of increased limb disparity. In this respect, pterosaurs appear unique amongst flying vertebrates in that their disparity seems to have peaked relatively late in clade history. Comparative analyses also show that there is little evidence that the evolutionary diversification of pterosaurs was in any way constrained by the appearance and radiation of birds.

Reichel, M., Schultz, C.L., and M.B. Soares. 2009. A new traversodontid cynodont (Therapsida, Eucynodontia) from the Middle Triassic Santa Maria Formation of Rio Grande Do Sul, Brazil. Palaeontology 52:229-250. doi: 10.1111/j.1475-4983.2008.00824.x

Abstract: Remains of a peculiar traversodontid cynodont, Protuberum cabralensis gen. et sp. nov., are described herein. The material was collected from two outcrops representing the Therapsid Cenozone (Middle Triassic) of the Santa Maria Formation, and consists of a cranium with most of its dentition preserved and an associated postcranial skeleton. The upper postcanines have two sharp cusps that are connected by a medial crest on unworn postcanines. The specimens possess several autapomorphies, including: (1) presence of thickened bone on the dorsal surface of the skull; (2) thick dorsal ribs, with remarkable processes situated on their dorsal borders that decrease in size distally; and (3) an iliac blade with a series of rugosities along its dorsal border. The lumbar ribs bear overlapping costal plates and have distally projecting rib shafts that differ from the pattern observed in Thrinaxodon, Pascualgnathus and Cynognathus.

NSF Problems

As if things weren't bad enough with shrinking budgets.....




Two Great New Finds

...and they are not fossils. I'm taking a short break here from Triassic fossils to talk about one of my other major interests, the American Civil War (1861-1865). My great-great-great grandfather joined the northern (Union) army in April of 1861 right after the war started. He served in the 1st Connecticut Volunteer regiment, a three months unit hastily organized to put down the southern rebellion (by the way...that does make me a Yankee, although I have relatives on both sides of the conflict). Because the 1st Connecticut Volunteer Infantry was only in existence for a little of three months and only fought in a single engagement (the Battle of Bull Run or Manassas in July 1861) there is not much information available on this unit besides the official regimental history and a single newspaper image from Harpers Weekly (see below).
Even though the 1st Connecticut Volunteers fought at Bull Run (which was the first major battle of the American Civil War), they had a minor and not very flattering role in the battle (they half-heartedly charged up a hill and then ran away), and again not much information can be found.

My personal interest in the 1st Connecticut and the battle of Bull Run is a result of receiving copies of my great-great-great grandfather's war correspondence about 20 years ago. The letters are an extremely detailed, at least four pages each and written almost daily, of the camp life of a soldier and is essentially the day to day history of the regiment. Because of this I am actually one of the few (if not the only) expert on the history of this regiment. Unfortunately, although the letters are detailed up the the Battle of Bull Run, there are no letters the few days prior to the battle and no details given afterwards (maddeningly he tells his wife he will give her the details when he gets home!).

I have spent quite a bit of time over the last 15 years collecting books and pieces of information on the regiment and the battle. One key account is an out-of-print book called "Wooden nutmegs at Bull Run", a humorous 1872 book written by a soldier in the 3rd Connecticut Volunteers (who fought alongside my ancestors regiment). This book is only available on microfiche in a Connecticut historical museum (very far from Arizona). By the way, Connecticut is the nutmeg state, hence the name.

However, just two weeks ago I came across two very key resources in my search for information. First I found a reprint copy of "Wooden Nutmegs" on Amazon.com! There is a book series called the Gale Archival Editions on Demand that provides copies of out-of-print historical texts (much like Google Books is doing now, although only PDFs). Secondly, I found out that my ancestor has a set of diaries preserved at a Connecticut museum. I was able to order PDFs made from microfiche copies of the diaries and these turned out to be a veritable gold mine. Not only did he write letters home (which I already had), but he kept a day to day "war journal" which contains much information not in the letters including all of the information leading up to, during, and right after the battle. These are filling in numerous holes in the regimental history and of my ancestors role. Amazing! Prior to two weeks ago I had no idea that these even existed.

It is incredible to read the actual day to day account of a soldier fighting in a war over 140 years ago and experience exactly what these men went through. Even more fun is matching his letters and diaries to written history and seeing how they match, my great-great-great grandfather even saw Abraham Lincoln! I am slowly transcribing all of this information and one day plan to write a book on his experience and his regiment. At some point I'll have to get back to my Triassic studies......

Late Triassic Mystery Fossil #5

OK...this really is a mystery fossil because I am not really sure what it is. It was collected in 2002 from Petrified Forest National Park in the Blue Mesa Member of the Chinle Formation. It was found in a bluish mudstone layer that contains lots of in-situ tree stumps but hardly any vertebrate fossils. This layer occurs just below an extremely productive horizon which produces a wealth of typical Chinle vertebrates (phytosaurs, aetosaurs, metoposaurs, etc...).

I'm sorry for the slightly blurry photo and only one angle but that is all I have right now. I first thought that it was a scapula, but I guess that it could also be a paroccipital process of the opisthotic and a portion of the exocipital of a pseudosuchian archosaur. The scale bar = 5 cm.

I'm open to either other suggestions and/or votes on my hypotheses.

Revised Chinle Stratigraphy of the Chama Basin

ResearchBlogging.org
Zeigler, K. E., Kelley, S., and J. W. Geissman. 2008. Revisions to stratigraphic nomenclature of the Upper Triassic Chinle Group in New Mexico: New insights from geologic mapping, sedimentology, and magnetostratigraphic/ paleomagnetic data. Rocky Mountain Geology 43:121-141. DOI: 10.2113/gsrocky.43.2.121

This is a recent paper with some interesting and possibly key implications for stratigraphic correlations in the Chinle Formation. Historically, stratigraphic correlation for Late Triassic non-marine rocks in western North America has been accomplished mainly through the use of biostratigraphy (e.g., Camp, 1930 [phytosaurs]; Colbert and Gregory, 1957 [vertebrates]; Litwin et al., 1991 [palynomorphs]; Good, 1993 [invertebrates], Lucas, 1993 [vertebrates]); however, these biostratigraphic-based correlations have not been unambiguous and are often contested and revised (e.g., Long and Murry, 1995; Langer, 2005; Rayfield et al., 2005; Hunt et al. 2005; Parker, 2006). More recent studies (e.g., Riggs et al. 1996; Zeigler, 2008; Irmis and Mundil, 2008; Dickinson and Gehrels, 2008) generating isotopic dates as well as magnetostratigraphic data may be more reliable to provide correlations and reconstruct Late Triassic paleogeography. However, much of this work is in preliminary stages and/or unpublished outside of dissertations and/or abstracts. Nonetheless, some important resolutions have been made regarding the Late Triassic of the southwest U. S. such as confirming that the lower portion of the Glen Canyon Group is Triassic in age and not Jurassic (Molina-Garza et al. 2003), providing isotopic ages for the Chinle Formation (Riggs et al., 2003; Irmis and Mundil, 2008); and reconstructing the Chinle-Dockum River systems (Riggs et al. 1996; Dickinson and Gehrels, 2008).

Zeigler et al. (2008) examine the sedimentology and magnetostratigraphy of the Chinle Formation in the Chama Basin of north central New Mexico. This area is well known for its paleontology containing no less than four major vertebrate quarries (Canjilon, Snyder, Coelophysis, and Hayden) and the areas have produced the type materials of several taxa including Coelophysis bauri, Eucoelophysis baldwini, Typothorax coccinarum, and Dromomeron romeri (e.g., Colbert, 1989; Hunt and Lucas, 1993; Long and Murry, 1995; Sullivan and Lucas, 1999; Zeigler et al., 2003; Irmis et al., 2007). Furthermore, this area has produced the vast majority of known dinosauromorph (including dinosauriforms and dinosaurs) material from the Late Triassic (e.g., Colbert, 1989; Irmis et al., 2007). Thus, correlating these deposits to the rest of the Chinle Basin is of extreme importance.



In the Chama Basin, the members of the Chinle from oldest to youngest are the “Mottled Strata”, Agua Zarca Sandstone, Salitral Shale tongue, Poleo Sandstone Lentil, Petrified Forest Member, and the Siltstone Member (Stewart et al. 1972). Lucas (1993) raised the Chinle Formation to group status and correlated the Agua Zarca “Formation” to the Shinarump “Formation” and the siltstone member (erroneous termed the Red Siltstone Member by Zeigler et al. 2008) to the Rock Point “Formation”. This last correlation has been highly contested with other workers (e.g., Dubiel, 1989) suggesting correlation with the Owl Rock Member instead. In later papers, Lucas and colleagues (e. g., Lucas et al., 2003) separated out various members of the Salitral “Formation” and the Petrified Forest “Formation”. It is important to note that the Coelophysis Quarry is situated in the siltstone member; whereas the Snyder, Canjillon, and Hayden Quarries are in the Petrified Forest Member. Based on stratigraphic position and vertebrates Lucas (1993) correlated the siltstone member (his Rock Point) with the Redonda Formation (Dockum Group) in eastern New Mexico and the Poleo Sandstone to the Sonsela Sandstone of northeastern Arizona. Finally, Heckert and Lucas (2003) formally named the “Mottled Strata” the Zuni Mountains Formation.

One of the goals of Zeigler et al. (2008) was to test some of these correlations using geological mapping magnetostratigraphy and provide the following results:

1) The Zuni Mountain Formation is not mappable at the 1:24000 scale and thus is not a valid formation.

2) The various proposed members of the Salitral and Petrified Forest “Formations” cannot be distinguished by mapping and therefore are rejected.

3) The Poleo Sandstone is of almost entirely reverse polarity whereas the Sonsela Sandstone bed is of normal polarity and therefore cannot be correlative. [Note that this is the same bed which Jeff Martz and I now call the Jasper Forest bed of the Sonsela Member].

4) The siltstone member is predominantly of normal polarity whereas the type Rock Point (in Utah) and the Redonda Formation are of reverse polarity. Thus the siltstone member is not assignable to the Rock Point, nor is it correlative with the Redonda.

5) The siltstone member (and thus the Coelophysis Quarry) shares a paleo pole position with the lower part of the Moenave Formation of the Glen Canyon Group, which has alternatively been considered to be Triassic or Jurassic.

These conclusions reveal limitations of relying solely on biostratigraphy to correlate non-marine stratigraphic units. Late Triassic terrestrial fossils do have biostratigraphic utility, however, more work needs to be done (e.g., larger sample sizes) to determine accurate stratigraphic ranges of taxa, and this work needs to be done in concert with detailed palynology, magnetostratigraphic, stratigraphy, and anchored with robust isotopic dates.

One aspect of the Zeigler et al. (2008) paper that confuses me is the rank of the Chinle (and Kate and I have discussed this numerous times). In the beginning of the paper they suggest that because Spencer Lucas did not propose his change in rank for the Chinle in peer-reviewed literature, usage of Chinle Group for all non-marine Upper Triassic strata in the western U. S. is not valid. However, without any real justification or explanation they then ‘formally’ raise the Chinle to group rank only in the Chama Basin. When I mentioned this to a Chinle Formation veteran colleague of mine he exclaimed that this would only make things more confusing and Chinle nomenclature was already confusing enough. I have to agree. I really do not see the utility in raising the Chinle to group rank at all, nevermind in such a small portion of the formation. Now if one uses Chinle Group they will have to state whether this is sensu Lucas (1993) or sensu Zeigler et al. (2008). I am really not sure how any of this will be resolved.

Overall the new paper by Zeigler et al. (2008) provides intriguing hypotheses regarding the Chinle Formation and emphasizes how much work is left to do on that unit.

The photo above is of the Hayden Quarry in the Petrified Forest Member and is from here.

REFERENCES

Camp, C. L. 1930. A study of the phytosaurs with description of new material from western North America. Memoirs of the University of California, 10:1-174.

Colbert, E. H. 1989. The Triassic dinosaur Coelophysis. Museum of Northern Arizona Bulletin 57:1-160.

Colbert, E. H., and J. T. Gregory. 1957. Correlation of continental Triassic sediments by vertebrate fossils. Geological Society of America Bulletin 68:1458-1467.

Dickinson, W. R., and G. E. Gehrels. 2008. U-Pb ages of detrital zircons in relation to paleogeography: Triassic paleodrainage networks and sediment dispersal across southwest Laurentia. Journal of Sedimentary Research 78:745-764.

Dubiel, R.F. 1989. Depositional environments of the Upper Triassic Chinle Formation in the eastern San Juan Basin and vicinity, New Mexico. U.S. Geological Survey Bulletin 1801B:1-22.

Good, S. 1993. Molluscan paleobiology of the Upper Triassic Chinle Formation, Arizona and Utah. Unpublished PhD Dissertation, University of Colorado, Boulder.

Heckert, A. B., and S. G. Lucas. 2003. Triassic stratigraphy in the Zuni Mountains, west-central New Mexico. New Mexico Geological Society Guidebook 54:245-262.

Hunt, A. P. and S. G. Lucas, S.G. 1993. Stratigraphy and vertebrate paleontology of the Chinle Group (Upper Triassic), Chama Basin, north-central New Mexico. New Mexico Museum of Natural History Bulletin 2:61-69.

Hunt, A. P., Lucas, S. G., and A. B. Heckert. 2005. Definition and correlation of the Lamyan: A new biochronological unit for the non-marine late Carnian (Late Triassic). New Mexico Geological Society Guidebook, 56:357-366.

Irmis, R. B., and R. Mundil. 2008. New age constraints from the Chinle Formation resolve global comparisons of Late Triassic vertebrate assemblages. Journal of Vertebrate Paleontology 28:95A.

Irmis, R. B, Nesbitt, S. J., Padian, K., Smith, N. D., Turner, A. H, Woody, D., and A. Downs. 2007. A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs. Science 317:358–361.

Langer, M. C. 2005. Studies on continental Late Triassic tetrapod biochronology. II. The Ischigualastian and a Carnian global correlation. Journal of South American Earth Sciences, 19:219-239.

Litwin, R. J., Traverse, A., and S. R. Ash. 1991. Preliminary palynological zonation of the Chinle Formation, southwestern U.S.A. and its correlation to the Newark Supergroup (eastern U.S.A.). Review of Palaeobotany and Palynology 68:269-287.

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.

Lucas, S. G. 1993. The Chinle Group: Revised stratigraphy and chronology of Upper Triassic non-marine strata in the Western United States. Museum of Northern Arizona Bulletin 59:27-50.

Lucas, S. G., Zeigler, K. E., Heckert, A. B. and A. P. Hunt. 2003. Upper Triassic stratigraphy and biostratigraphy, Chama Basin, north-central New Mexico: New Mexico Museum of Natural History and Science Bulletin 24:15-39.

Molina-Garza, R. S., Geissman, J. W., and S. G. Lucas. 2003. Paleomagnetism and magnetostratigraphy of the lower Glen Canyon and upper Chinle Groups, Jurassic-Triassic of northern Arizona and northeast Utah. Journal of Geophysical Research 108, B4, 2181: 1-24.

Parker, W. G. 2006. The stratigraphic distribution of major fossil localities in Petrified Forest National Park, Arizona. Museum of Northern Arizona Bulletin 62:46-61.

Riggs, N. R., Lehman, T. M., Gehrels, G. E., and W. R. Dickinson. 1996. Detrital zircon link between headwaters and terminus of the Upper Triassic Chinle-Dockum paleoriver system. Science 273:97-100.

Riggs, N. R., Ash, S. R., Barth, A. P., Gehrels, G. E., and J. L. Wooden. 2003. Isotopic age of the Black Forest Bed, Petrified Forest Member, Chinle Formation, Arizona: An example of dating a continental sandstone. Geological Society of America Bulletin 115:1315-1323.

Stewart, J. H., Poole, F. G. and R. F. Wilson. 1972. Stratigraphy and origin of the Chinle Formation and related Upper Triassic strata of the Colorado Plateau region, U.S. Geological Survey Professional Paper 690, 336 p.

Sullivan, R. M. and S. G. Lucas. 1999. Eucoelophysis baldwini, a new theropod dinosaur from the Upper Triassic of New Mexico, and the status of the original types of Coelophysis. Journal of Vertebrate Paleontology 19:81-90.

Zeigler, K.E. 2008. Stratigraphy, paleomagnetism, and magnetostratigraphy of the Upper Triassic Chinle Group, North-central New Mexico and preliminary magnetostratigraphy of the Lower Cretaceous Cedar Mountain Formation, Eastern Utah. Unpublished PhD dissertation, University of New Mexico, 224p.

Zeigler, K.E., and J.W. Geissman. 2008. Magnetostratigraphy of the Upper Triassic Chinle Group and Implications for the Age and Correlation of Upper Triassic Strata in North America. Geological Society of America Abstracts with programs (online).
http://a-c-s.confex.com/crops/2008am/webprogram/Paper47897.html

K. E. Zeigler, S. Kelley, J. W. Geissman (2008). Revisions to stratigraphic nomenclature of the Upper Triassic Chinle Group in New Mexico: New insights from geologic mapping, sedimentology, and magnetostratigraphic/paleomagnetic data Rocky Mountain Geology, 43 (2), 121-141 DOI: 10.2113/gsrocky.43.2.121

Zeigler, K. E., Heckert, A. B. and S. G. Lucas. 2003. Paleontology and Geology of the Upper Triassic Snyder Quarry (Revueltian), North-Central New Mexico: New Mexico Museum of Natural History and Science Bulletin 24, 132 p.

Free GSA Bulletin and Geology PDFs

Wow, the free PDFs just keep coming. Thanks to Paul Heinrich who posted this information on the Dinosaur Mailing List.

"For an unknown period of time free PDF files of papers published in "Geology" and "Geological Society of America Bulletin" can be downloaded free of charge.

A person can access them using the search page at:
http://gsabulletin.gsapubs.org/search.dtl

and the archive pages at:
http://gsabulletin.gsapubs.org/archive/

and

http://geology.gsapubs.org/archive/"

I checked it out and it works.

Happy Downloading.

New Pterosaur Volume Honoring Peter Wellnhofer Now Available

NOW AVAILABLE...

Flugsaurier: Pterosaur papers in honour of Peter Wellnhofer. 2008. Hone, D.W.E., and Buffetaut, E. (eds). Zitteliana B 28. 264pp.

CONTENTS...

Wellnhofer, P. A short history of pterosaur research. p7-19.

Padian, K. Were pterosaur ancestors bipedal or quadrupedal?: Morphometric, functional and phylogenetic considerations. p21-33.

Hone, DW.E., & Benton, M.J. Contrasting supertrees and total-evidence methods: pterosaur origins. p35-60.

Barrett, P.M., Butler, R.J., Edwards, N.P., & Milner, A.R. Pterosaur distribution in time and space: an atlas. p61-107.

Steel, L. The palaeohistology of pterosaur bone: an overview. p109-125.

Bennett, S.C. Morphological evolution of the wing of pterosaurs: mycology and function. p127-141.

Witton, M.P. A new approach to determining pterosaur body mass and its implications for pterosaur flight. p143-159.

Habaib, M.B. Comparative evidence for quadrupedal launch in pterosaurs. p161-168.

Elgin, R.E., Grau, C.A., Palmer, C., Hone, D.W.E., Greenwell, D., & Benton, M.J. Aerodynamic characters of the cranial crest in Pteranodon. p169-176.

Martill, D.M., & Witton, M.P. Catastrophic failure in a pterosaur skull from the Cretaceous Santana Formation of Brazil. p177-185.

Lockley, M., Harris, J.D., & Mirchell, L. A golobal overview of pterosaur ichnology: tracksite distribution in space and time. p187-198.

Unwin, D.M., & D.C. Deeming. Pterosaur eggshell structure and its implications for pterosaur reproductive biology. p199-207.

Martill, D.M., Witton, M.P., & Gale, A. Possible azhdarchoid remains from the Coniacian (Late Cretaceous) of England. p209-218.

Rodrigues, T., & Kellner, A.W.A. Review of the pterodactyloid pterosaur Coloborhynchus. p210-228.

Lu, J., Xu, L., & Ji, Q. Restudy of Liaoxipterus (Istiodactylidae: Pterosauria) with comments on the Chinese istiodactylid pterosaurs. p229-241.

Martill, D.M. First pterosaur remains from Exu Formation (Cretaceous) from the Araripe Basin, Brazil. p243-248.

Buffetaut, E. Late Cretaceous pterosaurs from France: a review. p249-255.

ORDERING INFO...

According to David Hone anyone who wants to order it should contact the publishers. The price is 29 Euros (plus postage). The volumes are still being printed and will be shipped around the end of January.

Contact:
Andreas TrenkleJörg-Tömlinger-Str. 2D-82152 PlaneggGermany Fax ++49-89-89329763 (inside Germany: 089-89329763)email: andreas@trenkle-buch.de

Please note that at this time the publisher does not accept credit cards.

Conodonts Squished by Thoughtless Dinosaurs

The 52nd annual meeting of the Palaeontological Association was held in December 2008 in the University of Glasgow. Although I was unable to attend (someday I will) the following poster presentation caught my eye. Probably not too many people are experts on World War I tunnels, stromatolites, conodonts, dinosaurs, and archosaur trackways but here is where all of these fields finally collide....

Belvedere, M., Mietto, P., Avanzini, M., and M. Rigo. 2008. Dinosaurs stepping on the conodont animals; p. 44 in Programme and Abstracts for the 52nd meeting of the Palaeontological Association. The Palaeontological Association Newsletter 69.

On the roof of a First World War tunnel in the Monte Pasubio (North Eastern Italy), on a supratidal stromatolitic bed of the Dolomia Principale Formation, 11 tracks have been found. Among them occur some clear dinosaurian tridactyl footprints, from small grallatorid-like to medium-large eubrontid, as well as some tetradactyl footprints. This formation contains the principal dinosaur footprints for the Triassic of the southern alps. All previous findings were on fallen blocks which, given the poor paleontological content of the formation, and the lack of precise stratigraphical position, made their biostratigraphical constraints very difficult to determine. In this case, for the first time, the trampled surface crops out in situ, about 500m from the bottom of the formation. Conodont sampling was carried out on the subtidal level just below the trampled surface. Unexpectedly, two conodonts were found: an advanced Epigondolella praeslovakensis and a true Mockina slovakensis, an association exclusive for the Middle Norian (latest Alaunian). Thus being so precisely contrained, the ichnoassociation could be used to date the other isolated blocks of the Dolomites. Moreover this co-occurrence of tetrpod footprints and conodonts can be used to confirm the Middle Norian age of the Eubrontes-Grallator biochron.

Dinosaur skeletons covered with ammonites have been found in marine strata , but as the authors state this is a first for conodonts and footprints. It's too bad that this does not happen more often to tie together marine and non-marine biostratigraphies. By the way, the small tridactyl tracks probably are ornithodiran as no self respecting pseudosuchian would stomp on conodonts ;).

My Favorite Kind of News Story

Mesalands Community College professor (and phytosaur expert) Axel Hungerbuehler is finding some great Late Triassic material in the Redonda Formation (Dockum Group) of New Mexico. Obviously I always get excited about the discovery of new aetosaur material.... oh yeah, there is some dinosaur material as well (which, of course, got the headline). Other related stories can be found here and here.

Students discover possible dinosaur fossil

By Thomas Garcia, Freedom New Mexico
January 13, 2009 - 9:21PM

A Mesalands Community College paleontology class has found a fossil that could be of a new form of Triassic reptile at an eastern New Mexico dig site. “I think that we have found a new form of aetosaurs,” said Axel Hungerbuehler, professor of Paleontology at Mesalands Community College.

The aetosaur, or eagle lizard, fossils were among numerous fossils excavated at a site in the Redonda formation in Quay County. Aetosaurs, a heavily armored plant-eater that lived in the Triassic period an estimated 200 Million years ago, are identified by the armor plating on their back and sides. Each of the plates has a distinct pattern and shape, Hungerbuehler said.

“The analysis of the armor plates found at the dig site indicates that we have found a new form of aetosaur,” Hungerbuehler said. In addition to the plates, they have identified bones of the internal skeleton of an aetosaur, including parts of the hip and several leg bones.

So far, however, no complete articulated skeletons have been excavated from the site, Hungerbuehler said.

Several more dinosaur-like elements, including another hip bone (pubis) and several hollow limb bones, were also recovered, Hungerbuehler said.

“These bones are not from the same individual dinosaur that was found in 2007,” Hungerbuehler said. “They could be fossils of a similar type of dinosaur.”

In 2007 a field class found a hip bone (ilium) of an un-named primitive dinosaur that was collected at the Redonda Formation site.

“We have not done enough examination of the fossil to determine if it is a new and previously undiscovered type of primitive dinosaur,” Hungerbuehler said. “A definite identification will be done once these fossils have been freed from their rocky host and they can be carefully cleaned.”

This all started during the summer of 2006, when three field classes and several volunteers of Mesalands Community College’s Dinosaur Museum started excavating bones of reptiles at the current dig site.

Hungerbuehler said an abundance of fossils were found in red and green siltstones, and sandstones of the Upper Triassic estimated to be 200 million years old. To date, about 250 field numbers have been recorded.

At the site they have found that bones occur in two different settings.

• In coarser layers of sandstones, bones are evenly distributed and show signs like breaking and abrasion, indicating they have been washed together by water currents.

• In red, fine-grained siltstones, undamaged bones have been found in spots of dense concentrations.

These probably represent skeletons that fell apart at the spot. Many of the bones still await preparation.

Items identified from the records kept in the field and the bones already freed from the rock in Mesalands Community College’s Dinosaur Museum Lab include:

• Phytosaurs — semiaquatic crocodile-like reptiles - two phytosaur skulls and parts of a large lower jaw were recovered, plus numerous bones of the body.

• Large carnivorous reptile, A large reptile, perhaps, a rauisuchian (Rau’s crocodiles) which includes the largest predators in the Late Triassic, is represented by the tip of a lower jaw. The element is currently under study by students at Mesalands to confirm the identity

Relaunch of Stuttgarter Beiträge zur Naturkunde Serie B as the open access journal Palaeodiversity

Thanks to Randy Irmis for bringing this to my attention. The journal Stuttgarter Beiträge zur Naturkunde Serie B has been relaunched as a new open access journal Palaeodiversity. The first issue was released in late 2008 and contains a new paper by Rainer Schoch on the phylogeny of the Capitosauria (the amount of temnospondyl work pubished in 2008 is just amazing!).

Also of great interest is that the journal site is offering free downloads of articles (including some Triassic articles) from back issues of Stuttgarter Beiträge zur Naturkunde Serie from 1999 with a promise that more will follow (www.palaeodiversity.org/backissues.htm).

Schoch, R. R. 2008. The Capitosauria (Amphibia): characters, phylogeny, and stratigraphy. Palaeodiversity 1:189-226.

Abstract - The phylogeny of the largest amphibians, the Triassic capitosaurs, is still much debated. One key taxon for the understanding of their relationships, Odenwaldia heidelbergensis from the Buntsandstein of Waldkatzenbach, is restudied here. A phylogenetic analysis performed on the basis of 66 characters and 25 taxa gives a new hypothesis of relationships. It rests to a large degree on previous data matrices, but many character codings have been changed with respect to new observations as well as the discovery of new taxa. The present data indicate that all classic capitosaur taxa do form a clade. The Capitosauria (all taxa more closely related to Parotosuchus than to Trematosaurus) excludes Benthosuchus and Edingerella but includes Wetlugasaurus, Sclerothorax, Watsonisuchus, Parotosuchus, and all other capitosaurs. All capitosaurs above Watsonisuchus are referred to as the Capitosauroidea, which includes Parotosuchus, Cherninia + Odenwaldia, Eryosuchus, Xenotosuchus, and a vast capitosaur crown clade. The crown includes two main branches: (1) the “Eucyclotosauria” (Cyclotosaurus, Kupferzellia, Procyclotosaurus, Stanocephalosaurus pronus) and (2) the “Paracyclotosauria” (Stanocephalosaurus birdi, Paracyclotosaurus, Mastodonsaurus, and the heylerosaurids Eocyclotosaurus and Quasicyclotosaurus). Stratigraphically, capitosaur phylogeny still reveals a rather poor match. However, the present phylogenetic hypothesis matches the stratigraphic ranges more precisely than the previous ones. The early branching between the “Eucyclotosauria” and “Paracyclotosauria” is more consistent with the fossil record than an alternative concept, in which Cyclotosaurus and the heylerosaurids form sister taxa (“Pancyclotosauria”). In any case, the otic fenestra and several other probably correlated features in the palate must have evolved two times independently within the crown capitosauroids.

Using Detrital Zircons to Reconstruct Chinle Paleogeography

Dickinson, W.R., and G.E. Gehrels. 2008. U-Pb Ages of Detrital Zircons in Relation to Paleogeography: Triassic Paleodrainage Networks and Sediment Dispersal Across Southwest Laurentia. Journal of Sedimentary Research 78:745-764.

Abstract - Integration of detrital zircon studies with data on biostratigraphy, isopachs, facies, and paleocurrents can improve reconstructions of paleogeography for ancient fluvial systems. U-Pb ages for 1808 individual detrital zircon grains in 20 samples of Triassic fluvial sandstone on the Colorado Plateau and High Plains, U.S.A., help constrain paleodrainage paths and patterns of sediment dispersal across southwest Laurentia. The dominant paleoflow was from southeast to northwest from sources as distant as the Ouachita orogen, and segments of Mesoamerica beyond it, to the Cordilleran margin in the Great Basin. Detrital zircons in Middle Triassic Moenkopi strata deposited along the distal eastern flank of the Sonoma foreland basin were derived from varied sources to the south and southeast, as were similar populations of detrital zircons in Upper Triassic Chinle strata exposed along the southern margin of the Colorado Plateau. Basal Chinle (-Dockum) strata of the High Plains to the east contain detrital zircon populations dominated by Cambrian grains derived from the nearby Amarillo–Wichita uplift, as do Gartra strata of northeast Utah to which the Cambrian grains were transported across eroded roots of Ancestral Rocky Mountains uplifts along upstream reaches of the Eagle paleoriver of northwest Colorado. The central locus of the Chinle–Dockum fluvial system lay along the tectonic furrow of an elongate backarc basin formed by dynamic subsidence inland from the Cordilleran magmatic arc. A lower Chinle–Dockum trunk paleoriver and the upper Chinle–Dockum Cottonwood paleovalley document longitudinal paleoflow parallel to the axis of the basin. Detrital zircon populations show that headwaters of both paleodrainages tapped the Ouachita orogen, the Permian–Triassic East Mexico arc, and associated rock assemblages of southwest Laurentia and adjacent Mesoamerica. Sediment sources in the Mesozoic Cordilleran arc became increasingly more prominent during Late Triassic time.
_________________________________________________________________

This is part of an ongoing project to reconstruct Triassic paleogeography using detrital zircons, especially the Chinle-Dockum paleoriver systems. The results reinforce the hypothesis of Riggs et al. (1996) that during early Chinle and Dockum deposition the two basins were linked by a single river system. One aspect of this paper that caught my eye is that the authors acknowledge the current confusion regarding ranks among Chinle-Dockum stratigraphic units, and leave this unresolved. Their results hinge on hypothesized unit correlations (supported in part by detrital zircon provenance), namely that the Sonsela, Poleo, and Trujillo sandstones are equivalents as are the Shinarump, Santa Rosa, and Agua Zarca. However, recent paleomag work by Kate Zeigler has suggested that the Sonsela and Poleo are probably not equivalent (Zeigler et al. 2008) and this work needs to be expanded to the other units. It is important to note however, that the "Sonsela" of Dickinson and Gehrels is only equivalent to a medial sandstone bed (Jasper Forest bed) in the expanded Sonsela Member of the Chinle (see Jeff Martz's detailed discussion of the stratigraphy of the Chinle in Petrified Forest National Park), and that other portions of the member may be Poleo equivalent. Nonetheless, the Dickinson and Gehrels paper is an important part of a plethora of new research projects that are clarifying the stratigraphy, biostratigraphy, and paleogeography of the Chinle and Dockum.

As part of this, I'm excited that the stratigraphic and biostratigraphic work being done in Petrified Forest National Park (and mentioned by Jeff), is being supplemented by paleomag work, isotopic dating, provenance work, chemostratigraphic work, and a host of sedimentological and paleosol studies. As a result of the work in the park and regional studies such as this, we are getting very close to finally being able to put together a detailed paleontological and geological history of the park, which will hopefully serve as a standard for the rest of the American southwest.

REFERENCES

Riggs, N. R., Lehman, T. M., Gehrels, G. E., and W. R. Dickinson. 1996. Detrital zircon link between headwaters and terminus of the Upper Triassic Chinle-Dockum paleoriver system. Science 273:97-100.

Zeigler, K. E., Kelley, S., and J. W. Geissman. 2008. Revisions to stratigraphic nomenclature of the Upper Triassic Chinle Group in New Mexico: New insights from geologic mapping, sedimentology, and magnetostratigraphic/paleomagnetic data. Rocky Mountain Geology 43:121-141.

I just gotta say this....

Unlike my colleague Jeff Martz I am not drinking myself into a stupor tonight because of some horrible singer, but reading through a few papers over the last few days has finally pushed me to the edge as well...and like Jeff I need to talk about this.

There are two errors, which should not be, that persistently show up in the Triassic literature. One is relatively minor but annoying, whereas the other is not only annoying but does have implications.

1) For the last 13 years Long and Murry (1995) has likely been the most cited paper for Late Triassic vertebrate paleontology. Prior to this Phillip Murry published quite a few papers dating back to the early 1980s on Triassic paleontology and Geology. His name, although uncommon, has only five letters in it. Why, with a simple name and numerous citations do many people continue to misspell his name (as Murray) in many papers? And why do the reviewers not catch this either? Again, nothing major but just annoying seeing it in paper after paper.

2) Having done my graduate work and published several papers concerning the aetosaur Desmatosuchus, I have noticed and continue to notice that despite being known by good material for over 80 years people continue to incorrectly assign material to this genus. Historically, any robust spiked aetosaur has been assigned to his taxon and that has caused much confusion; however, since 1985 the genus has been diagnosed using in part the ornamentation of its dermal osteoderms. Desmatosuchus is the only aetosaur genus that combines an ornamentation of randomly placed pits and grooves (with no radial patterning at all), a depressed anterior lamina (a smooth area of the osteoderm that underlies the preceding plate), and a centrally placed dorsal boss. This has been repeated numerous times in the literature yet I constantly come across material with a strong radial pattern being assigned to the genus. Last year a major Triassic exhibit opened in a major U. S. natural history museum. In this exhibit (which is for the most part very well done) Desmatosuchus is represented by an osteoderm, which has an extreme radial patterning, a posteriorly placed boss, and a raised anterior bar, the exact reverse of the diagnosis of Desmatosuchus.

When I was visiting museum collections on a very limited budget as a graduate student it was extremely frustrating to travel to institutions and then find out that all of the Desmatosuchus material was misidentified. It is even more frustrating to see this continuing, and yes it does have implications. Periodically you will see papers come out where comparisons with Desmatosuchus are being made, yet it quickly becomes apparent (at least to me) that the comparisons are based on a misidentified specimen. Desmatosuchus also possibly has some biostratigraphic significance, but again many voucher specimens for purported occurrences are based on misidentifications. Finally, a misidentification of material as Desmatosuchus eventually placed me in one of the most frustrating and unfortunate situations I have every found myself in in my entire life.

I do realize that misidentifications happen all the time with lots of fossils, however, it is unfortunate when it is done over and over again. Below are some representative plates and drawings of Desmatosuchus spurensis. The photographed material is MNA V9300. The drawings are from Long and Ballew (1985).





OK...rant over. Thanks for reading and please ID your Desmatosuchus material correctly.
REFERENCE
Long, R. A., and K. L. Ballew. 1985. Aetosaur dermal armor from the Late Triassic of southwestern North America, with special reference to material from the Chinle Formation of Petrified Forest National Park. Museum of Northern Arizona Bulletin 54:45-68.

Triassic Literature Recap - 2008

2008 was an excellent year for new and exciting infomation on the Triassic. Some highlights included two new (and somewhat conflicting) basal turtle discoveries, several new temnospondyls, a reexamination of "dinosaur superiority", ethical controversy, and finally several important dissertations. These dissertations as well as published abstracts promise that 2009 will be just as exciting.

This is not an entirely exhaustive list, but hopefully fairly complete. It does not include all geological papers or invertebrates. It was also cross-checked with Tracy Ford's dinohunter site.

By the way...the most prolific author for Triassic VP in 2008 is...... Mike Benton with five papers.

2008 Triassic Vertebrate Paleontology Literature

Brusatte, S.L., Benton, M.J., Ruta, M., and G.T. Lloyd. 2008. Superiority, competition, and opportunism in the evolutionary radiation of dinosaurs. Science 321:1485-1488.

Brusatte, S. L., Benton, M. J., Ruta, M., and G. T. Lloyd. 2008. The first 50 Myr of dinosaur evolution: macroevolutionary pattern and morphological disparity. Biology Letters, published online, 4pp.

Buffetaut, E., and M. Novak. 2008. A cyamodont placodont (Reptilia: Sauropterygia) from the Triassic of Solovenia. Palaeontology 51:1301-1306.

Butler, R. J., Upchurch, P., and D. B. Norman. 2008. The phylogeny of the ornithischian dinosaurs. Journal of Systematic Palaeontology 4:1-40.

Cisneros, J. C. 2008. Taxonomic status of the reptile genus Procolophon from the Gondwanana Triassic. Palaeontographic Africana 43:7-17.

Cisneros, J. C. 2008. Phylogenetic relationships of procolophonid parareptiles with remarks on thier geological record. Journal of Systematic Paleontology 6:345-366.

Cisneros, J. C. 2008. New basal procolophonid reptile from the Katberg formation (Lower Triassic) of the South African Karoo. Paleoworld 17:126-134.

Cleveland D. M., Nordt, L. C., and S. C. Atchley. 2008. Paleosols, trace fossils, and precipitation estimates of the uppermost Triassic strata in northern New Mexico. Palaeogeography, Palaeoclimatology, Palaeoecology 257:421-444.

Dalton, R. 2008. Fossil reptiles mired in controversy. Nature 451:510.

Damiani, R. 2008. A giant skull of the temnospondyl Xenotosuchus africanus from the Middle Triassic of South Aferica and its ontogenetic implications. Acta Palaeontologica Polonica 53:75-84.

Dias-da-Silva, S., Dias, E.V., and C.L. Schultz. 2009. First record of stereospondyls (Tetrapoda, Temnospondyli) in the Upper Triassic of Southern Brazil. Gondwana Research 15:131-136.

Diedrich, C. 2008. Millions of reptile tracks – Early to Middle Triassic carbonate tidal flat migration bridges of Central Europe – reptile immigration into the Germanic basin. Palaeogeography, Palaeoclimatology, Palaeoecology 259:410-423.

Dzik, J., Sulej, T., and G. Niedźwiedzki. 2008. A dicynodont−theropod association in the latest Triassic of Poland. Acta Palaeontologica Polonica 53:733–738.

Galton, P. M. 2008. Notes on the remains of archosaurian reptiles, mostly basal sauropodomorph dinosaurs, from the 1834 fissure fill (Rhaetian, Upper Triassic) at Clifton in Bristol, southwest England. Revue de Paleobiologie 26:505-591.

Heckert, A. B., Lucas, S. G., Rinehart, L. F., and A. P. Hunt. 2008. A new genus and species of sphenodontian from the Ghost Ranh Coelophysis Quarry (Upper Triassic: Apachean), Rock Point Formation, New Mexico, USA. Palaeontology 51:827-845.

Holmes, R., Cheng, Y.-N., and X.-C.Wu. 2008. New information on the skull of Keichuosaurus hui (Reptilia: Sauropterygia) with comments on sauropterygian interrelationships. Journal of Vertebrate Paleontology 28:76-84.

Hone, D. W. E., and M. J. Benton, M. J. 2008. A new genus of rhynchosaur from the Middle Triassic of South-West England. Palaeontology 51:95-115.

Irmis, R. B. 2008. Perspectives on the origin and early diversification of dinosaurs. PhD dissertation, Department of Integrative Biology, University of California, Berkeley, 421 pp.

Jenkins, F. A., Jr., Shubin, N. H., Gatesy, S. M., and A. 2008. Gerrothorax pulcherrimus from the Upper Triassic Fleming Fjord Formation of East Greenland and a reassessment of head lifting in temnospondyl feeding. Journal of Vertebrate Paleontology 28: 935–950.

Jiang, D.-Y., Motani, R., Hao, W.-C., Rieppel, O., Sun, Y.-L., Schmitz, L., and Z.-Y. Suny. 2008. First record of Placodontoidea (Reptilia, Sauropterygia, Placodontia) from the Eastern Tethys. Journal of Vertebrate Paleontology 28:904-908.

Jiang, D.-Y., Rieppel, O., Montani, R., Hao, W.-C., Sun, Y.-L., Schmitz, L., and Z.-Y. Sun. 2008. A new Middle Triassic Eosauropterygian (Reptilia, Sauropterygia) from Southwestern China. Journal of Vertebrate Paleontology 28:1055-1062.

Joyce, W. G., Lucas, S. G., Scheyer, T. M., Heckert, A. B., and A. P. Hunt. 2008. A thin-shelled reptile from the Late Triassic of North America and the origin of the turtle shell. Proceedings of the Royal Society B 276: 1656.

Kammerer, C. F., Flynn, J. J., Ranivoharimanana, L,. and A. R. Wyss. 2008. New material of Menadon besairiei (Cynodontia: Traversodontidae) from the Triassic of Madagascar. Journal of Vertebrate Paleontology 28:445-462.

Knoll, F. 2008. On the Procompsognathus postcranium (Late Triassic, Germany). Geobios 41:779-786.

Li, C., Wu, X.-C., Rieppel, O., Wang, L.-T., and L.-J. Zhao. 2008. An ancestral turtle from the Late Triassic of southwestern China. Nature 456:497-501.

Liu, J., Soares, M. B., and M. Reichel. 2008, Massetognathus (Cynodontia, Traversodontidae) from the Santa Maria Formation of Brazil. Revista Brasileira de Paleontologia 11:27-36.

Lucas, S. G., and L. H. Tanner. 2008. Reexamination of the end-Triassic mass extinction; pp. 66-103 in Elewa, A. M. T. (ed.), Mass Extinction. Springer-Verlag Publishers, Heidelberg, Germany.

Maisch, M. W., Jiang, D.-y., Hao, W.-c., Sun, Y.-l., Sun, Z.-y., and H. Stöhr. 2008. A well-preserved skull of Qianichthyosaurus zhoui Li, 1999, (Reptilia: Ichthyosauria) from the Upper Triassic of China and the phylogenetic position of the Toretocnemidae. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 248:257-266.

Mancuso, A. C., and C. A. Mariscano. 2008. Paleoenvironments and taphonomy of a Triassic lacustrine system (Los Rastros Formation, central-western Argentina). Palaios 23: 535-547.

Martz, J.W. 2008. Lithostratigraphy, chemostratigraphy, and vertebrate biostratigraphy of the Dockum Group (Upper Triassic), of southern Garza County, West Texas. Unpublished PhD dissertation. Texas Tech University, Lubbock, 504p.

Modesto, S. P., and J. Botha-Brink, J. 2008. Evidence of a second, large archosauriform reptile in the Lower Triassic Katberg Formation of South Africa. Journal of Vertebrate Paleontology 28:914-917.

Motani, R., Jiang, D.-Y., Tintori, A., Sun, Y.-L., Hao, W.-C., Boyd, A., Hinic-Frlog, S., Schmitz, L., Shin, J.-Y., and Z.-Y. Sun. 2008. Horizons and assemblages of Middle Triassic Marine reptiles from Panxian, Guizhou, China. Journal of Vertebrate Paleontology 28:900-903.

Nesbitt, S. J., and S. Chatterjee. 2008. Late Triassic dinosauriforms from the Post Quarry and surrounding areas, west Texas, USA. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 249:143-156.

Nesbitt, S.J., and M.R. Stocker. 2008. The vertebrate assemblage of the Late Triassic Canjilon Quarry (Northern New Mexico, USA) and the importance of apomorphy based assemblage comparisons. Journal of Vertebrate Paleontology 28:1063-1072.

Parker, W.G. 2008. Description of new material of the aetosaur Desmatosuchus spurensis (Archosauria: Suchia) from the Chinle Formation of Arizona and a revision of the genus Desmatosuchus. PaleoBios 28:1-40.

Parker, W. G., and B. J. Barton. 2008. New information on the Upper Triassic archosauriform Vancleavea campi based on new material from the Chinle Formation of Arizona. Palaeontologia Electronica 11.3.14a, 20pp.

Parker, W.G., Stocker, M.R., and R.B. Irmis. 2008. A new desmatosuchine aetosaur (Archosauria: Suchia) from the Upper Triassic Tecovas Formation (Dockum Group) of Texas. Journal of Vertebrate Paleontology 28:692-701.

Peyer, K., Carter, J. G., Sues, H.-D., Novak, S. E., and P. E. Olsen. 2008. A new suchian archosaur from the Upper Triassic of North Carolina. Journal of Vertebrate Paleontology 28:363-381.

Renesto, S. 2008. Remains of a juvenile phytosaur from the Late Triassic of northern Italy. Rivista Italiana di Paleontologia e Stratigrafia 114:155-160.

Richter, M., and C. E. V. Toledo. 2008. The first Triassic lungfish from South America (Santa Maria Formation, Parana Basin) and its bearing on geological correlations within Pangaea, pp. 43-54 in Cavin, L., Longbottom, A., and M. Richter, M. (eds.) Fishes and the Break-up of Pangaea. The Geological Society Special Publication 295.

de Ricqles, A., Padian, K., Knoll, F., and J. R. Horner. 2008. On the origin of high growth rates in archosaurs and thier ancient relatives: complementary histological studies on Triassic archosauriforms and the problem of a "phylogenetic signial" in bone histology. Annales de Paleontologie 94:57-76.

Rieppel, O., Li, C., and N. C. Fraser. 2008. The skeletal anatomy of the Triassic protosaur Dinocephalosaurus orientalis Li from the Middle Triassic of Guizhou Province, Southern China. Journal of Vertebrate Paleontology 28: 95-110.

Ruta, M., and J. R. Bolt. 2008. The brachyopoid Hadrokkosaurus bradyi from the early Middle Triassic of Arizona, and a phylogenetic analysis of lower jaw characters in temnospondyl amphibians. Acta Palaeontologica Polonica 53:579-592.

Säilä, L. K. 2008. The osteology and affinities of Anomoiodon liliensterni, a procolophonid reptile from the Lower Triassic Bundsandstein of Germany. Journal of Vertebrate Paleontology 28:1199-1205.

Scheyer, T. M. 2008. Aging the oldest turtles: the placodont affinities of Priscochelys hegnabrunnensis. Naturwissenschaften 95:803-810.

Schoch, R. R. 2008. A new stereospondyl from the German Middle Triassic, and the origin of the Metoposauridae. Zoological Journal of the Linnean Society 152:79-113.

Sidor, C., Miller, M., and J. Isbell. 2008. Tetrapod burrows from the Triassic of Antarctica: Journal of Vertebrate Paleontology 28: 277-284.

Sidor, C. A., Damiani, R., and W. R. Hammer. 2008. A new temnospondyl from Antarctica and a review of Fremouv Formation biostratigraphy. Journal of Vertebrate Paleontology 28:656-663.

Spielmann, J. A., Lucas, S. G., Rinehart, L. F., and A. B. Heckert. 2008. The Late Triassic Archosauromorph Trilophosaurus. New Mexico Museum of Natural History and Science Bulletin 43:1-177.

Stein, K., Palmer, C., Gill, P. G., and M. J. Benton. 2008. The aerodynamics of the British Late Triassic Kuehneosauridae. Palaeontology 51:967-981.

Stocker, M. R. 2008. The relationships of the phytosaur Leptosuchus Case 1922 with descriptions of new material from Petrified Forest National Park, Arizona. Unpublished M.S. Thesis, University of Iowa, Iowa City, 220p.

Sues, H.-D., and R. R. Reisz. 2008. Anatomy and phylogenetic relationships of Sclerosaurus armatus (Amniota: Parareptilia) from the Buntsandstein (Triassic) of Europe. Journal of Vertebrate Paleontology 28:1031-1042.

Surkov, M. V., and M. J. Benton. 2008, Head kinematics and feeding adaptations of the Permian and Triassic dicynodonts. Journal of Vertebrate Paleontology 28:1120-1129.

Valais, S. de, and R. N. Melchor. 2008. Ichnotaxonomy of bird-like footprints: an example from the Late Triassic-Early Jurassic of northwest Argentina. Journal of Vertebrate Paleontology 28:145-159.

Voight, S., Buchwitz, M., Fischer, J., Krause, D., and R. Georgi. 2008. Feather-like development of Triassic diapsid skin appendages. Naturwissenschaften

Wang, X., Bachmann, G. R., Hagdorn, H., Sanders, P. M., Cuny, G., Chen, X., Wang, C., Chen, L., Chen, L., Meng, F., and G. Xu, G. 2008. The Late Triassic Black Shales of Guanling area, Guizhou Province, South-West China: a unique marine reptile and pelagic crinoid fossil lagerstatte. Palaeontology 51:27-61.

Weinbaum, J. C. 2008. Review of the Triassic reptiles Poposaurus gracilis and Postosuchus kirkpatricki (Reptilia: Archosauria). Unpublished PhD dissertation, Texas Tech University, 183.

Whitside, D. I., and J. E. A. Marshall. 2008. The age, fauna and palaeoenvironment of the Late Triassic fisure deposits of Tytherington, South Gloucestershire, UK. Geological Magazine 141:105-147.

Witzmann, F., and T. Gassner. 2008. Metoposaurid and mastodonsaurid stereospondyls from the Triassic-Jurassic boundary of Portugal. Alcheringa 32:37-51.

Witzmann, F., Schoch, R. R., and M. W. Maisch. 2008. A relict basal tetrapod from Germany: first evidence of a Triassic chroniosuchian outside Russia: Naturwissenschaften 95:67-72.

Witzmann, F. and R. Soler-Gijón. 2008. The bone histology of osteoderms in temnospondyl amphibians and in the chroniosuchian Bystrowiella. Acta Zoologica. Early Online. DOI: 10.1111/j.1463-6395.2008.00385.x.

Zeigler, K.E. 2008. Stratigraphy, paleomagnetism, and magnetostratigraphy of the Upper Triassic Chinle Group, North-central New Mexico and preliminary magnetostratigraphy of the Lower Cretaceous Cedar Mountain Formation, Eastern Utah. Unpublished PhD dissertation, University of New Mexico, 224p.

Zeigler, K. E., Kelley, S., and J. W. Geissmann. 2008. Revisions to stratigraphic nomenclature of the Upper Triassic Chinle Group in New Mexico: New insights from geologic mapping, sedimentology, and magnetostratigraphic/paleomagnetic data. Rocky Mountain Geology 43:121-141.

Zhao, L., Sato, T., and C. Li. 2008. The most complete pistosauroid skeleton from the Triassic of Yunnan, China. Vertebrata PalAsiatica 82:283-286.

Was Postosuchus bipedal or quadrupedal?

My post presenting a new reconstruction of Postosuchus kirkpatricki generated some discussion on whether or not Postosuchus was an obligate biped or quadrupedal. Jeff Martz’s reconstruction (below and revised from the earlier post) is based on research by Jonathan Weinbaum arguing the former (Weinbaum, 2008). In his dissertation Jonathan provides several lines of evidence which he feels clearly demonstrates that Postosuchus is bipedal. This includes a shortened forelimb with an extremely reduced manus, elongate and narrow pubes and ischia (a condition which he claims is only found in bipeds), and the presence of hyposphenes and hypantra in the dorsal vertebrae (which restrict lateral movement and were at one time believed to only occur in dinosaurs, although I showed in 2008 that they also occur in quadrupedal aetosaurians). Some more compelling evidence presented by Weinbaum (2008) is the structure of the brain endocast which is very similar to that of bipedal dinosaurs. He also used a vertebral analysis tool developed by Christian and Preuschoft (1996), which demonstrates that vertebrae are enlarged in areas of support. Quadrupeds show two enlargement areas, whereas bipeds show only one. Postosuchus shows only a single peak above the pelvis, typical for bipeds. Jonathan is not the first to suggest this. Sankar Chatterjee, in his initial description of Postosuchus (Chatterjee, 1985), also suggested that it was bipedal based on a short trunk and forelimbs. He also showed that the forelimb/hindlimb ratio in Postosuchus was similar to the theropod Ornitholestes; however, according to the published dataset (which only includes a few taxa), the ratio is much higher than in other theropods such as Coelophysis, Allosaurus, and Albertosaurus, which are bipedal as are all theropods.

Weinbaum (2008) also looked at forelimb/hindlimb length ratios, and provided a ratio of .59 for Postosuchus, which he claimed falls between that Gallimimus and Deinonychus. Despite Weinbaum’s (2008) claims, I feel that the forelimb is not really that much shorter than the hindlimb (i.e. .59), and thus not conclusive evidence. Again, however, this was a very limited dataset. I would like to see comparisons with more taxa from a variety of archosauromorph clades as both Chatterjee (1985) and Weinbaum (2008) found that Postosuchus has a similar ratio to some of the longest limbed coelurosaurs rather than all theropods in general. I do not find this compelling.

All other workers (e.g., Long and Murry, 1995) have suggested that Postosuchus is quadrupedal (see reconstruction from Wikipedia below), which is how all other non-poposaurid “rauisuchians” have been portrayed. This is mainly based on track evidence, where the ichnotaxon Cheirotherium has been ascribed to a “rauisuchian” trackmaker. Cheirotherium tracks were made by a quadrupedal non-ornthodiran archosaur with a highly reduced manus. Furthermore, Peyer et al. (2008) argued that although the manus is extremely reduced, the pectoral girdle of Postosuchus is robust suggesting that it was used in locomotion.

However, there is trackway evidence that possibly supports bipedal Postosuchus. Olsen and Huber (1998) described tracks in the Upper Triassic Pekin Formation (which includes Postosuchus) as matching well with the pes of Postosuchus and having no sign of a manus impression.

Was Postosuchus capable of bipedal movement? Based on limb ratios and other lines of evidence, yes. Was it an obligate biped? Unfortunately we cannot say for certain as the available data is ambiguous. What is needed is a similar study as that conducted by Bonnan and Senter (2007) for “prosauropods”. These authors argued that as quadrupedal animals must pronate the forelimb for it to provide propulsion, evidence for this must be found to support this type locomotion (or the opposite to support bipedalism). Until a similar study is conducted for Postosuchus, I would say that the case is far from closed.

REFERENCES

Bonnan, M. F., and P. Senter. 2007. Were the basal sauropodomorph dinosaurs Plateosaurus and Massospondylus habitual quadrupeds? Special Papers in Palaeontology 77:139-155.

Chatterjee, S. 1985. Postosuchus, a new thecodontian reptile from the Triassic of Texas
and the origin of tyrannosaurs. Philosophical Transactions of the Royal Society of London, Series B 309, 395-460; London.

Christian, A., and H. Preuschoft. 1996. Deducing the body posture of extinct large vertebrates from the shape of the vertebral column. Palaeontology 39:801-812.

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.

Olsen, P. E. and Huber, P., 1998, The oldest Late Triassic footprint assemblage from North America (Pekin Formation, Deep River basin, North Carolina, USA). Southestern Geology, v. 38, no. 2, p. 77-90.

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100 Best Blogs for Earth Science Scholars

Well, Chinleana made a list of 100 best blogs for Earth Science Scholars, as did many of my colleagues on my blogroll. I'm honored to be included in this company and glad that people are enjoying my ramblings.

Anyhow, check it out as there is a great list of informative earth science blogs listed here [dead link 3/25/2013].