More on Postosuchus kirkpatricki

Postosuchus kirkpatricki was named by Chatterjee (1985) for rauisuchian material from the Post Quarry in the Upper Triassic Dockum Group of Texas. Based on pelvic morphology Chatterjee assigned Postosuchus to the Poposauria. He also noticed strong convergences between Postosuchus and carnosaurian (at the time, large) dinosaurs and argued that Postosuchus was an ancestral carnosaur despite the presence of a crocodilian ankle. However, this was not the first material of a large rauisuchian collected from the American southwest. Case (1943) described a partial pelvis of what he considered to be an aberrant phytosaur from the Dockum Group, and even earlier Charles Camp had collected over 100 bones of a large rauisuchian from the Placerias Quarry in the Chinle Formation of east-central Arizona. In the early 1980s Robert Long collected more material from Petrified Forest National Park (PEFO) and was actively studying the Arizona material, which he planned on naming “Lythrodynastes rectori” (after the superintendent of PEFO) and later “Lythrodynastes rapax” (“greedy gore-lord”). However, these plans were waylaid by the publication of Postosuchus in 1985 (which is named after the town of Post Texas that was named for the nearby cereal plant). After comparing the Arizona material to the type material of Postosuchus, Long conceded that the material all belonged to the same taxon; however, he also noted that the type material was chimaeric and consisted of three different animals (Murry and Long, 1989). Long and Murry (1995) formally named the shuvosaurid “Chatterjeea elegans” (now Shuvosaurus inexpectatus), and the poposaur Lythrosuchus langstoni from portions of the original Postosuchus holotype material. As a result Postosuchus is no longer considered to be a poposaurid. Most of the Arizona material still remains undescribed and in fact the material reposited at the Museum of Northern Arizona still bears the name “Lythrodynastes rapax”.

About 10 years ago Jonathan Weinbaum started repreparing the type material (especially the skull) of Postosuchus, discovering a nearly complete skull under layers of paint, chicken wire, and plaster. His resulting MS thesis (Weinbaum, 2002) and PhD Dissertation (Weinbaum. 2008) provide the most up-to-date and accurate reconstruction of Postosuchus kirkpatricki. In 2008 Peyer et al. described a partial skeleton of a new species, Postosuchus alisonae, from the Upper Triassic of North Carolina. The reconstruction provided by Jeff Martz is based on these works.

Two side notes regarding the taxonomy of Postosuchus. The pelvis described by Case (1943) was found and donated to the University of Michigan Museum of Paleontology by a Texas rancher named William J. Elliot, who aided Case often in his fieldwork and found and donated several specimens from the area around Spur, Texas. At the very end of his 1943 paper, Case asks that “if, as is possible, more abundant material should show this pelvis to be that of a new genus or species it is suggested that the name of Mr. Wm. J. Elliot be associated with it, in recognition of his interest in the local geology and the help he has given many collectors in the Triassic beds of Texas”. To date, this request has never been granted.

Finally, Chatterjee (1985) named Postosuchus kirkpatricki for Mr. and Mrs. Kirkpatrick, therefore by ICZN conventions the specific name should actually be P. kirkpatrickorum. Since 1985 nobody has provided an emendation and the current volume of the code is ambiguous about whether an emendation should be made (as just recently discussed on the Dinosaur Mailing List).

The next post will discuss the bipedal/quadrupedal controversy...

The photo is the Petrified Forest National Park mount based on Robert Long's concept of "Lythrodynastes rapax". Photo is from here.

REFERENCES

Case, E. C. 1943. A new form of phytosaur pelvis. American Journal of Science 241:201–203.

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.

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.

Murry, P. A., and R. A. Long. 1989. Geology and paleontology of the Chinle Formation, Petrified Forest National Park and vicinity, Arizona and a discussion of vertebrate fossils of the southwestern Upper Triassic; pp. 29-64 in Lucas, S. G., and A. P. Hunt (eds.), Dawn of the Dinosaurs in the American Southwest, University of New Mexico Press, Albuquerque.

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.

Weinbaum, J. C. 2002. Osteology and relationships of Postosuchus kirkpatricki (Archosauria: Crurotarsi). Unpublished MS thesis, Texas Tech University, 78pp.

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

New Triassic Critter Reconstruction II

Here is another new Late Triassic critter reconstraction from the Chinle/Dockum courtesy of Jeff Martz. As with the last one I'll leave the ID up to you with discussion to follow.

Congratulations Randy

At this time I would like to congratulate my good friend and colleague Randy Irmis, who just finished his dissertation (Irmis, 2008) at UC Berkeley and is moving to Utah to start his new job as an assistant professor in the Department of Geology and Geophysics at the University of Utah and curator of the Utah Museum of Natural History. Best of luck Randy!


This picture is from his University of Utah faculty webpage.

REFERENCE

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.

Happy Holidays

Petrified Forest Fieldwork Photos - 2008

All of this nasty ice and freezing weather has me longing for summer and fieldwork again. Here are some photos from work in the park this past summer to warm us up a little. The above photo is a picture of a phytosaur skull excavation from May of this year.

Here is our fossil preparator Matt Brown precariously perched excavating a small metoposaurid skull.

Summer intern Kate Hazlehurst working on some poposaurid material from the Sonsela Member.

Poposaurid pubis in-situ.

Myself and Matt Brown carving (literally) a phytosaur skull out of its sandstone tomb. This complete skull is from the type locality of Pseudopalatus jablonskiae and may belong to the same taxon.

Me again, with intern Joanna Panosky excavating aetosaur (Typothorax) plates.


One of the Typothorax plates.

Just to rub it in a little, all of these sites are within an hour drive/hike of my office. Such is the beauty of the Petrified Forest National Park. Hope these warmed you up a bit (at least those of us in the Northern Hemisphere).

The vertebrate assemblage of the Late Triassic Canjilon Quarry and the importance of apomorphy based assemblage comparisons

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.

ABSTRACT—The Upper Triassic Canjilon Quarry in northern New Mexico preserves a vertebrate assemblage typical of the Norian Stage of North America. Although dominated in relative abundance by the phytosaur Pseudopalatus and the aetosaur Typothorax, a more diverse assemblage of smaller forms was previously reported. Additions to the Canjilon
Quarry vertebrate assemblage are critically reviewed and described using an apomorphy-based method for assigning taxa. An apomorphy-based approach for compiling and comparing assemblages allows each taxonomic assignment to be a testable hypothesis. Fragmentary yet diagnostic elements that may not be assignable to a species-level taxon can be assigned to a larger clade and thus provide useful information. Additionally, each taxon listed in the assemblage must be tied to a diagnostic specimen listed with a museum specimen number. Using this method for the Canjilon Quarry, we establish the presence of an assemblage that is more similar to other vertebrate quarries near Ghost Ranch than previously thought. The Canjilon Quarry assemblage is restricted to vertebrates from UCMP locality V2816. Vertebrate material housed at the Museum of Comparative Zoology, Harvard, which was reported from the Canjilon Quarry, was not collected from UCMP V2816 but from a nearby locality.

The Canjilon Quarry from the Petrified Forest Member (Chinle Formation) of New Mexico was mainly worked by Charles Camp and crew (University of California, Berkeley) in 1933 and produced a wealth of fossil vertebrate material, most notably numerous skeletons (including a suite of skulls) of the phytosaur Pseudopalatus. You can get more information on the Canjilon Quarry, including an extremely detailed reconstruction of the 1933 excavation from field notes, here and here. Of course the main point and overall importance of this paper is the discussion on using apomorphy based identifications when creating faunal lists.

New Triassic Critter Reconstructions

Not only is Jeff Martz a really good geologist and paleontologist he also is very skilled as an illustrator (check out his M.S. thesis Martz [2002], his skeletal reconstruction of Desmatosuchus [from Parker, 2008], and this link at Discovery News for other examples of his work). Jeff has recently initiated a new series of Late Triassic animal reconstructions from Petrified Forest National Park and has generously offered to let me share some of them on my site rather than showing them on his site. The park has been sorely lacking up-to-date reconstructions of many of its Triassic animals, as most existing reconstructions date from the 1980s and do not include the majority of new finds. This is the first of the series and I won't tell you what taxon this is. Instead I'll leave to you to guess its identity.
These represent slightly different reconstructions of the same animal. It is challenging to try to provide realistic yet thought provoking reconstructions, especially regarding skin color, texture, and soft tissue. The coloration and patterning of most animals fall into a few broad catagories including camouflage, disruptive patterning, and/or sexual display. The animal featured here is most likely a carnivore and thus was provided with more of a disruptive pattern that would allow the animal a mechanism to distract prey by making the body outline hard to see, and thus distance and speed difficult to judge. The upper reconstruction adds hypothesized soft parts including a 'dewlap' and other features which may or may not have been present, and thus are speculative yet feasible for display.

As long as Jeff is willing, I hope to provide more of these new reconstructions in the future.

REFERENCES

Martz, J.W. 2002. The morphology and ontogeny of Typothorax coccinarum (Archosauria, Stagonolepididae) from the upper triassic of the American Southwest. Unpublished M.S. thesis. Texas Tech University, Lubbock.

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.

Chinle Silesaurid and the Importance of Field Notes

Adam Yates nailed it. The specimen is the proximal end of the right femur of a silesaurid (PEFO 34347) from the Upper Triassic Blue Mesa Member (Chinle Formation) of Arizona. This specimen is significant because it represents the only known unambiguous silesaurid element from the lower portion of the Chinle Formation and from Arizona. It demonstrates that silesaurids were a portion of the fauna at Petrified Forest National Park.

This specimen was discussed in more detail by Parker et al. (2006) and Nesbitt et al. (2007). It is identical to the proximal ends of the femora of Silesaurus opolensis (Carnian of Poland) and Eucoelophysis baldwini (Norian of New Mexico) and thus cannot be assigned to a specific genus although the age (Norian) and stratigraphic position (Chinle Formation) of the specimen would suggests that it is probably could represent Eucoelophysis rather than Silesaurus. However, until more material is found this cannot be considered. A key characteristic of the proximal end of the femur in Silesaurus, Eucoelophysis, and PEFO 34347 is that the element is triangular in proximal view and has a mediolaterally trending sulcus. Whereas this sulcus is present in other taxa, most notably the pseudosuchian Shuvosaurus, the femur of silesaurids differs in having a subrectangular femoral head in lateral view with a slightly offset head as in dinosaurs.

Now for the promised “interesting” (and frustrating) story regarding this specimen. This specimen was collected sometime in the late 1990s by an unknown individual who was part of a larger research project. It went unrecognized and was included in a large amount of material deemed unworthy of study and potentially to be disposed of. When going through this material to see if anything was salvageable I came across this specimen. Unfortunately, the exact spot where the specimen was collected was not recorded. There are no known field notes for the project and field tags contain minimal information, in this case just a vague geographical reference. This reference is enough to pinpoint the specimen to a small geographical area and limited stratigraphic level; however, it will be nearly impossible to find the rest of the specimen if it exists (and the break is clean, suggesting that more of the specimen was preserved and awaits discovery).

I cannot emphasize enough (and I stress this to, and require it from, all of my employees and interns) the importance of collecting and recording accurate field data on every specimen collected whether the specimen seems important or not. I don’t know how I would function without my past field notes when it comes to identifying and interpreting specific specimens. I have found when I get lax (because of time, weather, arrogance, etc..) I usually end of regretting not having a key piece of information regarding a specimen at some point. At the absolute minimum for EVERY specimen collected there should be GPS coordinates, a photograph of the site showing the surrounding landscape (most important), and a brief description of the sediments and stratigraphic position. Taphonomic notes are also extremely important and often forgotten. Bottom line, you cannot collect too much information. Anyone who has worked with older specimens when simply a stratigraphic unit and state were deemed sufficient information will understand. PEFO 34347 currently represents to earliest known silesaurid from North America, yet its provenance cannot be precisely determined and clarification regarding this specimen depends exclusively on luck. Was more of the specimen preserved? Is it still present and will we be able to stumble across it? I certainly hope so.

REFERENCES

Nesbitt, S.J., Irmis, R.B., and W.G. Parker. 2007. A critical re-evaluation of the Late Triassic dinosaur taxa of North America. Journal of Systematic Palaeontology 5:209-243.

Parker, W.G., Irmis, R.B., and S.J. Nesbitt. 2006. Review of the Late Triassic dinosaur record from Petrified Forest National Park, Arizona. Museum of Northern Arizona Bulletin 62:160-161.

Late Triassic Mystery Fossil #4

This is an interesting specimen with an interesting history.....and proof that, to be cliche, one person's junk is another person's treasure (especially if they don't know what they are looking at). Unfortunately that is only half the story, the rest is highly frustrating. Views are lateral and proximal. Scale bar is 1 cm.

First record of stereospondyls from the Upper Triassic of Brazil

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. doi:10.1016/j.gr.2008.07.002

Abstract - Stereospondyls survived the Permo-Triassic extinctions in a refuge probably located in the landmass that nowadays comprises Australia. Subsequently, they radiated to other parts of Pangaea, reaching their highest distribution and diversification during the Early Triassic. An incomplete interclavicle from the Caturrita Formation represents their first record in the Upper Triassic of Brazil. Previously, Upper Triassic South American stereospondyls were restricted to Argentina. This new record reinforces a former hypothesis that suggests the presence of a more diverse stereospondyl fauna in South America during the Late Triassic than previously assumed. Additionally, the presence of a stereospondyl and a phytosaur in the Caturrita Formation reinforces the hypothesis of a change to more humid climatic conditions in the Paraná Basin during the Upper Triassic. The record of Early Triassic stereospondyls in South America suggests that they first colonized Brazil and/or Uruguay, spreading from South Africa during the Early Triassic, subsequently reaching Argentina. Up till now, there is no record of Middle Triassic stereospondyls in either Argentina and Brazil, probably due to either taphonomic bias or insufficient prospecting. Despite the lack of direct evidence, one should not dismiss an earlier stereospondyl colonization of Argentina still during the Early or Middle Triassic.

Feather-like development of Triassic diapsid skin appendages

Thanks to Rob Taylor of the Theropod Archives who just posted on the Dinosaur Mailing List that Naturwissenschaften is freely available online through the end of the month. One of several Online First Titles that is of interest is this one...

Voight, S., Buchwitz, M., Fischer, J., Krause, D., and R. Georgi. Online First 2008. Feather-like development of Triassic diapsid skin appendages. Naturwissenschaften
DOI 10.1007/s00114-008-0453-1

Abstract - Of the recent sauropsid skin appendage types, only feathers develop from a cylindrical epidermal invagination, the follicle, and show hierarchical branching. Fossilized integuments of Mesozoic diapsids have been interpreted as follicular and potential feather homologues, an idea particularly controversially discussed for the elongate dorsal skin projections of the small diapsid Longisquama insignis from the Triassic of Kyrgyzstan. Based on new finds and their comparison with the type material, we show that Longisquama’s appendages consist of a single-branched internal frame enclosed by a flexible outer membrane. Not supporting a categorization either as feathers or as scales, our analysis demonstrates that the Longisquama appendages formed in a two-stage, feather-like developmental process, representing an unusual early example for the evolutionary plasticity of sauropsid integument.

The PDF and online supplemental material is also available from the same site.

Looking at Aetosaurs in a Whole New Way

Jeff Martz's recent post at Paleo Errata reminded me of this recent article which came out two months ago. Check it out, you can tell that the writer had a lot of fun with this, and the photo (see courtesy photo from http://www.santafenewmexican.com/ below) is great.

Of course, one comment made in the article regarding the similarity to modern crocodiles led to a Google search which turned up what could best be described as um....., you got it, croc porn.

All of this aside, what a great specimen of Typothorax!

On the Procompsognathus postcranium

F KNOLL (2008). On the Procompsognathus postcranium (Late Triassic, Germany)☆ Geobios, 41 (6), 779-786 DOI: 10.1016/j.geobios.2008.02.002

ABSTRACT - A review of the historical background of the material housed in the Staatliches Museum für Naturkunde (Stuttgart) and ascribed to Procompsognathus triassicus (Upper Triassic, Germany) is provided. The systematic position of the postcranial remains is discussed. The combined results of cladistic analyses suggest that the type material, an incomplete postcranial skeleton in two pieces (SMNS 12591), is from a theropod close to Segisaurus and Coelophysis. An isolated manus (SMNS 12352a) is definitely not theropodan, but could be from any small basal archosaur. The remarkable diversity of the carnivorous guild that dwelled in southern Germany before the end-Triassic events is underlined.

This is the latest paper in the Procompsognathus saga, regarding the taxonomic status of four specimens refered to this taxon, a purported theropod dinosaur, from the Late Triassic of Germany. To recap, Fraas (1913) named Procompsognathus triassicus based on a partial skeleton (SMNS 12591a) and skull (SMNS 12591), and refered it to the Dinosauria. Huene (1921) discussed the material further and assigned another partial skull (SMNS 12352) and manus (SMNS 12352a) from the same quarry to the taxon. Since that time this material has been reviewed by Ostrom (1981), Sereno and Wild (1992), Chatterjee (1993, 1998), Rauhut and Hungerbuhler (2000), Rauhut (2003), Allen (2004), and most recently by Knoll and Schoch (2006) which was an abstract previewing the current study by Knoll. All of these authors came to differing conclusions regarding the taxonomic affinities of the material as listed below:

Ostrom (1981)
SMNS 12591 - Procompsognathus triassicus
SMNS 12591a - Procompsognathus triassicus
SMNS 12352 - non Procompsognathus triassicus
SMNS 12352a - non Procompsognathus triassicus

Sereno and Wild (1992)
SMNS 12591 - Theropod similar to Coelophysis and Segisaurus
SMNS 12591a - Saltoposuchus connectens (Crocodylomorpha)
SMNS 12352 - Saltoposuchus connectens
SMNS 12352a - Saltoposuchus connectens

Chatterjee (1993, 1998)
SMNS 12591a - Theropod (contra Sereno and Wild [1992])

Rauhut and Hungerbuhler (2000)
SMNS 12591 - Theropod similar to Coelophysis and Segisaurus

Rauhut (2003)
Procompsognathus is a theropod but a metataxon

Allen (2004)
Procompsognathus is a non-dinosaurian ornithodiran

Knoll and Schoch (2006)
SMNS 12591 - Theropod similar to Coelophysis and Segisaurus
SMNS 12591a - Theropod, possibly tetanuran
SMNS 12352 - indeterminate crocodylomorph
SMNS 12352a - indeterminate crocodylomorph

The current paper (Knoll, 2008) follows the finding of Knoll and Schoch (2006) except that the isolated manus (SMNS 12352a) is considered to represent an unknown basal archosaur. Thus Knoll (2008) argues for a previously unrecognized diversity of carnivorous archosaurs in the Upper Triassic Stubensandstein. Hopefully this is the final word, but given the numerous differing hypotheses put forth this taxonomic argument may never be fully resolved.

The image is from here.

REFERENCES

Allen, D. 2004. The phylogenetic status of Procompsognathus revisited. Journal of Vertebrate Paleontology 24:34A.

Chatterjee, S. 1993. Procompsognathus from the Triassic of Germany is not a crocodylomorph. Journal of Vertebrate Paleontology 13:29A.

Chatterjee, S. 1998. Reassessment of the Procompsognathus skull, p. 6 in Wolberg, D.L., Gittis, K., Miller, S., Carey, L., and A. Raynor (eds.), Dinofest International. The Academy of Natural Sciences, Philadelphia.

Fraas, E. 1913. Die neuesten Dinosaurierfunde in der schwabischen Trias. Die Naturwissenschaften 1:1097-1100.

Huene, F.v. 1921. Neue Pseudosuchier und Coelurosaurier aus dem wurttembergischen Keuper. Acta Zoologica 2:329-403.

Knoll, F., and R. Schoch. 2006. Does Procompsognathus have a head? Systematics of an egnimatic Triassic taxon. Journal of Vertebrate Paleontology 26:86A.

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

Ostrom, J.H. 1981. Procompsognathus - theropod or thecodont? Palaeontographica A 175:175-195.

Rauhut, O.W.M. 2003. The interrelationships and evolution of basal theropod dinosaurs. Special Papers in Palaeontology 69:1-213.

Rauhut, O.W.M., and A. Hungerbeuhler. 2000. A review of European Triassic theropods. GAIA 15:75-88.

Sereno, P.C., and R. Wild. 1992. Procompsognathus: theropod, "thecodont", or both? Journal of Vertebrate Paleontology 12:435-458.

Proofing The Proof Corrections?

OK...this has happened to me more than once so I would like to comment and hopefully receive some feedback. You send in your final revisions for your manuscript and it is accepted by a journal. Sometime later you receive the proofs with the layout for final publication and a request for you to check it over and correct any final typos and/or problems with the layout. You submit your proposed changes within the time alloted and sometime later the manuscript is finally published. Upon reading through the published manuscript you see where some but not all of the changes you requested in the proofs were made, and thus there may still be some annoying errors (typos and/or layout) that you thought were going to be fixed. I am not talking about major changes being requested (which are costly at the proof stage and thus may not be approved by the editors). Instead this is about small corrections that for some reason were not made.

What do you do next? Of course you can contact the editors and point out were requested corrections were not made, but what does this approach get you? An apology and possibly an erratum in the next issue, but does not fix the actual publication (which is now a permanent record). Maybe it is possible to actually proof the proof corrections? I'm not aware of any journal that does this, but I may start asking.

I guess that hypothetically through the writing, review, and rewriting stages all mistakes should have been eliminated, however, anyone who publishes knows that this is not the case. In fact, the proof stage is one of the most important parts of the whole process because it represents the first time the manuscript has been out of the author's control and as I said earlier it represents the permanent record of your work. Wouldn't you like just one last look before it finally does print? I actually had one manuscript a few years back where we did not even get proofs! The final result was not good and we actually felt obliged to add a disclaimer to the reprints and PDFs that we distributed.

Has anyone else had a problem with this? How common is this type of error?

Polish Dragon - Revisited

Back in August I briefly discussed the find of a large theropod and dicynodont from a quarry in Lisowice in southern Poland. This find is significant because it represents the latest stratigraphical unambiguous occurrence of a dicynodont in the Late Triassic, as well as the possible earliest occurrence of a tetnuran theropod. The peer-reviewed article detailing this find is now out in Acta Palaeontologica Polonica.

I still need to read through the paper to comment some more but in the meantime here is the abstract:

It is generally accepted that during the Triassic the composition of tetrapod faunas underwent a series of fundamental transformations, mainly as a result of diversification of
archosaurs and decline of therapsids (Benton 1994, 2004, 2006). The last herbivorous basal synapsids, dicynodonts, disappeared from the record in the early Norian of the
Americas, about 220 Ma (Langer et al. 2007), being unknown from the Late Triassic of Europe. Here, we report a partially articulated skeleton and isolated bones of a giant
rhino−size dicynodont in the Upper Triassic fluvial sediments at Lisowice (Lipie Śląskie clay−pit) in southern Poland. Paleobotanical data indicate an early Rhaetian age for
the fauna (Dzik et al. 2008; Niedźwiedzki and Sulej 2008). The dicynodont bones are associated with bones of carnivorous dinosaurs, pterosaurs, as well as capitosaur and plagiosaur amphibians. Dicynodonts were represented in the Germanic Basin throughout the Late Triassic, as proven by findings of smaller dicynodonts in older deposits in the same area, associated there with temnospondyl amphibians. It appears, thus, that the fossil record of tetrapod succession in the Late Triassic was strongly controlled by ecological factors and biased by uneven representation of particular environments. The Lisowice assemblage proves that faunas dominated by dicynodonts did not entirely disappear at least until the end of the Triassic.

REFERENCE

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

Rethinking Turtle Origins - Odontochelys

What an exciting time it must be to work on basal turtles. Hot on the heels of Chinlechelys and Eileanchelys comes a new basal turtle, Odontochelys semitestacea, from the Norian (~220 Ma) of China. The article and commentary came out today in the journal Nature and you can also read about it here and here.

Odontochelys predates other earliest known turtles by at least 5 million years and is from marine rocks suggesting a marine origin for turtles. The complete fossil (see these photos from the Nature News website), known from four specimens, possesses a ventral plastron but not a dorsal carapace suggesting that the plastron formed first (but see argument by Reisz and Head, 2008).

Finally, as also hinted at by the name, Odontochelys is the first known turtle to possess teeth.

Whereas, the marine origin is surprising given the terrestrial nature of other Triassic turtles overturning what was thought to be a stable hypothesis, the teeth are a nice find, but not so surprising given that turtles must have originated from a toothed reptilian ancestor.

As to the ventral carapace forming first, Reisz and Head (2008) argue against the interpretation provided by Li et al. (2008); however, based on a statement made by Li that "here, in our hands, there is an ideal missing link for turtle evolution. It has no osteoderms on its back, but only ossified neural [central] plates and expanded ribs." I wonder if what we are looking at is a preservational artifact. Maybe the plastron fully ossifies earlier on in ontogeny. Not being a turtle specialist or seeing the specimens I may be completely wrong, but that is the explanation that first popped into my head.

Sounds like there is a lot more exploration and work to be done on basal turtles.

REFERENCES

Chun Li, Xiao-Chun Wu, Olivier Rieppel, Li-Ting Wang, Li-Jun Zhao (2008). An ancestral turtle from the Late Triassic of southwestern China Nature, 456 (7221), 497-501 DOI: 10.1038/nature07533

Robert R. Reisz, Jason J. Head (2008). Palaeontology: Turtle origins out to sea Nature, 456 (7221), 450-451 DOI: 10.1038/456450a

Pseudopalatus jablonskiae

rutgerjansma answered both quickly and correctly. Mystery fossil #3 is the holotype skull of the phytosaur Pseudopalatus jablonskiae named by myself and Randall Irmis in 2006. This skull was collected from the Sonsela Member of the Chinle Formation in Petrified Forest National Park. It was lying palate side up in a path used by archaeologists to access a ruined pueblo on a cliff top. Fortunately, Pat Jablonsky (a long time volunteer at the Denver Museum of Natural History, who was working as a ranger in the park at the time) recognized the specimen in the path and brought it to my attention. Unfortunately, it was pretty badly eroded (and trampled) and only the skull roof was still in-situ. The upper portion of the brain case was able to be reassembled by collecting the float. Preparation showed that it was a pseudopalatine phytosaur; however, it differed from other known pseudopalatines in possessing very anteroposteriorly short squamosal processes (seen in the photo below projecting from the back of the skull). In addition, the squamosal tips were not pointed and 'knob-like' as in other pseudopalatines, but more like the older Leptosuchus. This was supported by a character of the braincase, the entrance of an anterior projection of the squamosal into the lateral wall, another character of Leptosuchus (Camp, 1930). Finally, there is a small fossa around the supratemporal fenestra that is only seen in this specimen (autapomorphy). These characters and discussion with Axel Hungerbuehler (probably THE expert on phytosaurs) made us realize that this specimen was unique. Unfortunately, unique was definitely the right word here, because this incomplete skull is the only known specimen of P. jabloskiae.
However, earlier this summer a trip back to the quarry resulted in the discovery of the lower portion of the braincase of the holotype specimen. It had rolled away from the exposed skull and been buried, surfacing only this year. Subsequently another trip was made to the site to try to find more of the holotype and another, this time complete, skull of a phytosaur was found about 40 meters away and at the same horizon. This specimen has not been prepared yet but preliminary work during the excavation suggests that it may belong to P. jablonskiae. If so this would provide a description of the rest of the skull and further support the taxonomic validity of the species.

One more note. In our 2006 paper we state that P. jablonskiae is from just above the base of the Sonsela Member and therefore represents the lowest occurrence of Pseudopalatus in Petrified Forest National Park. However, reexamination of the Sonsela Member this summer by Jeff Martz figured out that the type locality for P. jablonskiae is higher in the Sonsela than previously believed, and that it occurs just above other localities that have provided specimens of another species of Pseudopalatus, P. pristinus. Thus, the newly recovered skull becomes even more important to test whether or not P. jablonskiae is restricted to a narrow horizon or represents a species that co-existed with P. pristinus.

The full description of P. jablonskiae can be found at Randall Irmis' CV page.

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.

Parker, W. G., and R. B. Irmis. 2006. A new species of the Late Triassic phytosaur Pseudopalatus (Archosauria: Pseudosuchia) from Petrified Forest National Park, Arizona. Museum of Northern Arizona Bulletin 62:126-143.

Late Triassic Mystery Fossil #3

Man I am busy (but aren't we all?), family, two jobs, research, upcoming holidays, and now studying for the GRE (I last took it 11 years ago!). Not too sure what I am thinking at times. Anyhow, I have not done one of these for awhile so here is Late Triassic mystery fossil #3. It comes from the Chinle Formation and is shown here in dorsal view. Hopefully I will post on this fossil and its relatives soon. I also know that there are a few new Triassic papers coming down the pipe soon, so there will be lot to cover in the next couple of months....but for now it is back to the quantitative section study guide.

New Paleontology Blog - Paleo Errata

I'd like to point out a new blog written by one of my colleagues, Dr. Jeff Martz, called Paleo Errata and found here: http://paleoerrata.blogspot.com/

I agree with Jeff that blogs are an excellent way to communicate and share ideas on a variety of topics, especially geology and paleontology. Like Jeff, I wholly support the sharing of information and open communication between researchers and hope that some day we all can do so freely without the fear of being betrayed. Developing professional relationships with colleagues including the sharing of unpublished information not only makes science fun, it is integral to doing good science. So much is going on "behind the scenes" and "in progress" that not being privy to such information inhibits our ability to formulate and test up to date hypotheses. Of course this involves a fair amount of trust that must be earned as well as given. There is plenty of material for everyone to work on and/or collaborate on without needing to rip each other off.

Jeff has offered to provide his unpublished ideas on various subjects on his blog and I would like to do the same from time to time here as well. Let's make an effort to open things up.

I just need everyone to promise not to...... ;)

Enigmatic Taxa I - Acallosuchus rectori

From time to time I'd like to introduce readers to some of the more 'interesting' Triassic critters. To start things off I will cover one of the more poorly known taxa, a mystery fossil in its own right, Acallosuchus rectori from the Chinle Formation of Arizona.

In his fieldnotes from May 22, 1923 Charles Camp discusses the discovery of what he described as the skull of "a small dinosaur or pterodactyl" from a quarry in what is today Petrified Forest National Park. His notes further state that he "plastered this and took it out but plaster broke off block and it had to be removed in pieces. Skull about 6 inches long. Part of rostrum broken" (Long and Murry, 1995). Accompanying this description is a field sketch of this "skull" (figure to the left taken from Irmis, 2005). According to Long and Murry (1995) when they rediscovered the specimen (in a cigar box) in the early 1980s the specimen bore almost no resemblance to Camp's field sketch. Still, what was preserved, although barely identifiable, is autopomorphic thus they felt justified to erecting a new taxon based on this material.

Previously the specimen was considered to represent a possible protrochampsid by Murry and Long (1989) who assigned a fragmentary postcranial skeleton (from probably the same locality) to their new taxon. However, by 1995 they had separated the material, naming the postcranial material Vancleavea campi, and the "skull" Acallosuchus rectori (Rector's ugly crocodile). We now know, based on new material (e.g., Hunt et al., 2002; Parker and Barton, 2008), what the skull of Vancleavea looks like and that this separation was indeed correct. Unfortunately, the skull is only known from a partial "mandible", and two other skull fragments which were interpreted as a portion of the frontal and postorbital, and a portion of the "postorbitojugal" bar by Long and Murry (1995).

Furthermore, Camp's sketch is unlike any known "reptile" skull, but as presented it would suggest that the element that Long and Murry (1995) identify as a dentary would actually be a maxilla. The large triangular opening would be an antorbital fenestra, above that a nasal and anteriorly (to the right on the drawing) possibly a premaxilla. The posterior opening could be an orbit, surrounded by a jugal/lacrimal bone anteriorly, and a postorbital dorsally? Unfortunately, the sketch does not provide clarification and was not labelled.

One of the autapomorphies of Acallosuchus is the presence of what Long and Murry (1995) described as osteoderms covering the surfaces of the skull. Irmis (2005) who further commented on this specimen and described these "osteoderms" as subtriangular knobs and noted that these knobs "are often arranged in rows running the length of the bone, and are themselves sculptured with longitudinal furrows. Other areas of bone not covered by these eminences are sculptured with additional grooves" (see photo below [from Irmis, 2005] of the dentary [occusal view] and another skull fragment [? view] showing these unique "knobs").



As discussed by Long and Murry (1995) and further commented on by Irmis (2005) the phylogenetic placement of this taxon is highly ambiguous. Long and Murry (1995) considered Acallosuchus to be a "neodiapsid" based on the presence of the "postorbitojugal bar"; however, even this identification is not unambiguous (Irmis, 2005) and will remain so without the discovery of more and better material.

One final note. Long and Murry (1995:193) named the species from ex-superintendent of Petrified Forest National Park Roger Rector, and his wife Betty, therefore the correct specific name would be A. rectororum; however, the current version of the ICZN does not require such emendations to be made, thus the name will stand as A. rectori. On a similar note I cannot believe that when such emendations were required that no none noticed that the 'rauisuchian' Postosuchus kirkpatricki was named by Chatterjee (1985) for the Kirkpatrick family and thus should probably have been P. kirkpatrickorum as well.

REFERENCES

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 B, 309:395-460.

Hunt, A. P., A. B. Heckert, S. G. Lucas, and A. Downs. 2002. The distribution of the enigmatic reptile Vancleavea in the Upper Triassic Chinle Group of the western United States. New Mexico Museum of Natural History & Science Bulletin, 21:269-273.

Irmis, R. B. 2005. The vertebrate fauna of the Upper Triassic Chinle Formation of Arizona. Mesa Southwest Museum Bulletin 9:63-88.

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.

Murry, P. A., and R. A. Long. 1989. Geology and paleontology of the Chinle Formation, Petrified Forest National Park and vicinity, Arizona and a discussion of vertebrate fossils of the southwestern Upper Triassic, p. 29-64. In S.G. Lucas and A.P. Hunt (eds.), Dawn of the Age of Dinosaurs in the American Southwest. New Mexico Museum of Natural History, Albuquerque, New Mexico.

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.

Royal Society Publishing Opens the Vault

Until February 1, 2009 Royal Society Publishing is partnering with Jstor to provide free access to the Royal Society Digital Archive, covering almost 350 years of publishing in a variety of disciplines including paleontology. This includes a large number of Triassic papers. You can access the archives at the link below:

http://journals.royalsociety.org/home/main.mpx

Information on the archive can be found here.

Happy hunting (and downloading)!

Dromomeron, the Hayden Quarry, and Cool Jobs!

These have been out for awhile, but I just became aware of them a little bit ago. Anyhow for those of you who are interested and haven't seen these, here are my Triassic colleagues Randy Irmis, Sterling Nesbitt, and Alex Downs discussing The Skinny on Naming a New Dinosaur, Fossil Hunters Roll the Bones for Clues, and Cool Jobs: Fossil Hunters. These clips are from the Discovery Channel and I found them here. Enjoy!

Chinle Confusion

The word 'nomenclature' (syn: terminology) is defined as “a system of terms used in a particular science” and allows for more precise communication and understanding of ideas. All scientific disciplines have established nomenclature (called ‘jargon’ by those outside of the discipline) and many have rules regarding the establishment of nomenclature. The Chinle Formation (mainly) of Arizona, Utah, and western New Mexico and the Dockum Group (mainly) of eastern New Mexico and western Texas are Late Triassic terrestrial units that are often correlated to each other on the basis of similar fossil content. Both have been widely studied by geologists and paleontologists since the beginning of last century and it is still debated whether the units were deposited within separate basins. Current thinking shows that the two depocenters may have been connected early in their history (Riggs et al., 1996) and separated later (Lehman and Chatterjee, 2005). The Dockum was named in 1890, the Chinle in 1917.

In 1993 Spencer Lucas advocated raising the name Chinle to Group status (and thus all of its constituent members to Formation rank). In doing so he reduced to Dockum in Texas to formational rank and included it within his Chinle Group. His rationale was that both units were the same age (based on fossils) and deposited in the same basin. It is important to note that he included all Late Triassic terrestrial rocks (including the Popo Agie Fm. of Wyoming) in his newly established group and eliminated some other older names (e.g., Dolores Fm. of Colorado). In later papers Lucas and colleagues completely abandoned use of the name Dockum as well. Lucas et al. (1985) argued that the term Dockum was meaningless, having been widely applied and lacks specificity as it used to include strata later determined to be Middle Triassic in age (Anton Chico Formation). Lucas argued that the term Chinle was better established; however, when originally defined, the Chinle contained units that are now considered to be Jurassic in age (Glen Canyon Group). Nonetheless, this is irrelevant as lithostratigraphic units can be time transgressive and do not need to be restricted by chronstratigraphic boundaries. Moreover, revising lithostratigraphic units does not invalidate them.

Furthermore, the term Dockum has long (since the 1890s) been generally understood to be restricted to Upper Triassic strata exposed around the southern High Plains in eastern New Mexico and west Texas. However, the term “Chinle” has been applied in a much more varied fashion, not only to the upper Triassic strata of the Colorado Plateau, but to strata in northern Utah and Colorado (e.g., Eagle Basin) deposited in a separate basin, and to strata within the Dockum Group which is probably only equivalent to parts of the Chinle Formation on the Colorado Plateau. However, by 1993 the scope of the term “Chinle” was well understood. Ironically the most confusing application of the term “Chinle” has been its extension to all Upper Triassic strata in the southwest by Lucas (1993), which has created two very different understandings of the term in the literature. Given that Lucas (1993) argued that the term Dockum should only be restricted to its type area in Texas, his radical extension of the term “Chinle” through the whole western U.S. is puzzling.

Nonetheless, since first being proposed in 1993, the use of Chinle as a Group has been published in hundreds of papers and abstracts by Lucas and colleagues and has also been used by a few other workers as well. There is also a large group of researchers who insist on leaving the Chinle at Formational rank, as well as researchers from Texas who refuse to abandon the term Dockum. Arguments as to why the Chinle should not subsume the Dockum were provided by Lehman (1994) and Dubiel (1994) and most recently addressed by Carpenter (1997) who wrote: “substituting one name for another (Chinle Group for Dockum Group) violates nomenclatural stability. Furthermore, as a stratigraphic unit, the Dockum Group is not defined by time” making the arguments by Lucas and colleagues “meaningless”. He then writes “the term Dockum Group must be retained, and because it has priority, can be used to encompass the Upper Triassic formations of the American southwest”. He also notes that because Upper Triassic formations in Colorado, Wyoming, and Idaho were most likely not deposited in the same basins as the Chinle or Dockum they should be left alone.

Although Carpenter (1997) was just making a point and not really advocating using the term Dockum in Arizona and Utah, this is where the issue of nomenclatural utility comes to play. Admittedly these names were erected at different times by different researchers who may not have been looking at all of the Triassic rocks in the western U.S. as a whole, but this does not negate their utility. When we hear the term Dockum we think Texas, whereas Chinle suggests Arizona., to mix the two only causes confusion. Even more so IMHO combining all of these units under a single name tells us nothing new scientifically, we already knew that they were roughly of the same age. In fact, again IMHO, “Chinle Group” appears to basically be synonymous with “Upper Triassic” and tells us nothing about local lithostratigraphic variation. This is contrary to Lucas’ (1993) stated intent to “simplify” the basic nomenclatural framework. Essentially, you have two groups of workers, one producing a plethora of papers in in-house bulletins and geological society guidebooks, independently utilizing two differing schemes. In summary, not only is one scheme considered to be against the North American Stratigraphic Code, the situation also creates serious confusion especially among outside researchers, as I will document next with a couple cases.

Weishampel et al. (2004) provide a listing of all known dinosaur occurrences along with their stratigraphic information. Under their Triassic section for North America they refer to the Chinle Formation, but also refer to the members within it also as formations (e.g., “Chinle Formation/Petrified Forest Fm”.). This is non-sensical as they are actually referring to the Petrified Forest Member of the Chinle Formation. Furthermore they list “Chinle Formation/Santa Rosa Fm” regardless of the fact that the Santa Rosa has never been considered a member of the Chinle Formation. Again this makes no sense and would only confuse workers with no familiarity with the conflicting schemes. It certainly does appear that Weishampel et al. (2004) were confused.

Cleveland et al. (2007, 2008a, 2008b) have recently published a series of papers documenting Late Triassic paleosols from New Mexico. The earliest paper (Cleveland et al., 2007) explicitly states that they prefer the nomenclature of Lucas (1993), and in the second paper (Cleveland et al., 2008a) this is implied. However, in the third paper (Cleveland et al., 2008b) they drop the Chinle back to Formational rank, presumably to move away from the Lucas nomenclature (although they do not state why), and return all lesser units back to member rank. Unfortunately, it is not this simple. For example, Cleveland et al. (2008b) now list one of their units as the Painted Desert Member of the Chinle Formation. No such member has ever been proposed. This is the Painted Desert Member of the Petrified Forest Formation of the Chinle Group according to Lucas (1993). Thus, Cleveland et als. (2008b) unit is actually the Petrified Forest Member (Chinle Formation). Likewise, upon dropping Chinle Group they do not appear to resurrect the term Dockum for their units in eastern New Mexico. This provides a similar scheme to that of Weishampel et al. (2004) where the Santa Rosa and Redonda Formations are considered part of the Chinle Formation (equal rank?). Clearly Cleveland and colleagues are confused by the changes in nomenclature and are possibly propagating more confusion. By the way, this is not meant to be a criticism of their paleosol work or general conclusions, I’m just pointing out the stratigraphic nomenclature confusion. Obviously I support their switch back to Chinle as a formational name. I have provided the nomenclature from thier 2007 (top center) and 2008b (bottom left) papers below as well as a rough correction of the 2008b figure (bottom right) below.

To wrap this up (it is already much longer than I planned). IMHO the scheme presented by Lucas (1993) has caused more confusion than clarification regarding the stratigraphic nomenclature of the Upper Triassic rocks in the western U.S. Also, others have argued that his scheme is against the North American Stratigraphic Code. I am not adverse to the Chinle Formation being raised to group rank, but I cannot do so at the expense of the name Dockum. Moreover, given how radically the meaning of the term “Chinle” was stretched by Lucas (1993), this might propagate more confusion. I am certain that my colleagues in Texas will not call their rocks “Chinle”, and rightfully so. Likewise, I would never dream of calling the rocks in Arizona “Dockum”, because of the confusion it would introduce. Maybe this calls for a special symposium to straighten out the issue, or maybe we should all just stop using Chinle Group. Many of the southwestern U.S. Triassic workers already have (or never adopted it to begin with) but it is important that this issue is brought to the attention of outside workers to help cease the confusion.

REFERENCES

Carpenter, K. 1997. A giant coelophysoid (Certosauria) theropod from the Upper Triassic of New Mexico, USA. N. Jb. Geol. Palaeont. Abh. 205:189-208.

Cleveland, D.M., Atchley, S.C., and L.C. Nordt. 2007. Continental sequence-stratigraphy of the Late Triassic (Norian-Rhaetian) Chinle strata, northern New Mexico: Allo- and autocyclic origins of paleosol-bearing alluvial successions: Journal of Sedimentary Research 77:909–924.

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

Cleveland, D.M., Nordt, L.C., Dworkin, S.I., and S.C. Atchley. 2008a. Pedogenic carbonate isotopes as evidence for extreme climatic events preceding the Triassic-Jurassic boundary: Implications for the biotic crisis? GSA Bulletin 120:1408-1415.

Dubiel, R. F. 1994. Triassic deposystems, paleogeography, and paleoclimate of the western interior; pp. 133-168 in Caputo, M.V., Peterson, J.A., and K.J. Franczyk (eds.) Mesozoic systems of the Rocky Mountain Region, USA. RMS-SEPM.

Lehman, T.M. 1994. Save the Dockum Group. West Texas Geological Society Bulletin 34:5–10.

Lehman, T. and S. Chatterjee. 2005. Depositional setting and vertebrate biostratigraphy of the Triassic Dockum Group of Texas. Journal of Earth System Science 114:325-351.

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

Lucas, S.G., Hunt, A.P., and M. Morales. 1985. Stratigraphic nomenclature and correlation of Triassic rocks in east-central New Mexico, a preliminary report. New Mexico Geological Society Guidebook 36:171-184.

Weishampel, D. B., Barrett, P. M., Coria, R. E., Le Loeuff, J., Gomani, E. S., Zhao Z., Xu X., Sahni, A., and C. Noto. 2004. Dinosaur Distribution, pp. 517-606 in Weishampel D. B., Dodson, P., and H. Osmólska, H. (eds.) The Dinosauria. 2nd edition. Univ. California Press, Berkeley.

Historic Election (non-Triassic topic)

Last night many of us witnessed a historic event (I find this link amusing) in the United States with the election of the first African-American president. This is a momentous occasion for all African-Americans (and other ethic groups) and hopefully shows that the United States has turned the corner in race relations and is a step closer towards stomping out bigotry and prejudice.

What was particularly impressive on me, and I hope to all Americans, was how much attention this election received worldwide. I know that my in-laws and friends in Canada (and colleagues in other countries) were following very closely and were glued to the TV coverage last night, as were some international co-bloggers. It was heartening when CNN switched coverage to show the reaction to the election of Obama in places like Kenya and Australia, as well as follow-up articles discussing this response. It is interesting, yet discouraging, to see such a contrast where most Americans pay little or no attention to elections in other countries, whereas many people in other countries have an interest in who is running the show in the U.S. Hopefully Americans will start to realize that in this age of globalization we need to be a partner with other countries and lose the "go it alone" or "with us or against us" attitude that has prevailed during the last eight years. It is clear that in the eyes of other global leaders and citizens Obama is the greatest "hope" for mending these damaged relationships and reconciling with our allies and supporters. Let's hope that we never allow pettiness or ego to let us stray so far again.

New Vancleavea Material

The current issue of Palaeontologia Electronica contains an article by myself and Bronson Barton describing some new material of the enigmatic archosauriform Vancleavea campi from Petrified Forest National Park. First off a disclaimer, it is no secret that two well-preserved skeletons from the Coelophysis quarry at Ghost Ranch New Mexico have been assigned to Vancleavea and are currently being described by Sterling Nesbitt, Michelle Stocker, Bryan Small, and Alex Downs. This new paper does not figure or discuss that material, and therefore does not contain the awaited reconstruction of this interesting animal. Instead this paper describes two partial skeletons from Petrified Forest National Park which contain postcrania not preserved in the holotype, discusses taxonomic issues, and provides a tentative phylogenetic analysis.


Vancleavea campi was named by Long and Murry (1995) based on a very fragmentary postcranial skeleton from the Upper Triassic Chinle Formation (Blue Mesa Member) of Petrified Forest National Park. Because of the incomplete nature of the material, Long and Murry (1995) could only assign the taxon to Neodiapsida incertae sedis. However, the taxon can be diagnosed by the presence of its characteristic osteoderms (see photo to the left) Additional material, including the Ghost Ranch specimens, was assigned to Vancleavea by Hunt et al. (2002) and Hunt et al. (2005) including additional material from near Stinking Springs in Arizona (Blue Mesa Member, Chinle Formation) assigned to a neodiapsid similar to Vancleavea by Polcyn et al. (2002). In addition, two partial skeletons were collected in 2004 from the Petrified Forest Member (Chinle Formation) of Petrified Forest National Park (Parker and Irmis, 2005). Subsequently, one of these specimens was the focus of a senior thesis by Bronson Barton and both are described in the new paper.

The tentative phylogenetic analysis suggests that Vancleavea campi is a derived non-archosaurian archosauriform. This is based mainly of the morphology of the femur (see photo bottom left) which has a sigmoidal shaft, distinct head, and lacks a intertrochanteric fossa. A very autopomorphic feature of Vancleavea is the morphology of the ilium (see photo bottom right) which differs significantly from that of all other known archosauriform taxa. In fact, the ilium of Vancleavea most superficially resembles that of drepanosaurid archosauromorphs.

Why is this new description necessary, especially when better material (i.e., the Ghost Ranch specimens) exists? Because the original type materials are so scrappy, it is important to supplement the type material with additional material from Petrified Forest National Park. Furthermore, if none of the new specimens (including the Ghost Ranch and Stinking Springs material) differ from the type material, yet differ from each other, then the type materials are nondiagnostic and the name Vancleavea would be a nomen dubium (Parker and Irmis, 2005). Thus, the description of this new material begins this process and is intended to provide future workers some tools to provide more detailed comparisons and to better determine the taxonomic status of the name Vancleavea.


REFERENCES

Hunt, A.P., Lucas, S.G., and Spielmann, J.A. 2005. The holotype specimen of Vancleavea campi from Petrified Forest National Park, Arizona, with notes on the taxonomy and distribution of the taxon. New Mexico Museum of Natural History and Science Bulletin , 29:59-66.

Hunt, A.P., Heckert, A.B., Lucas, S.G., and Downs, A. 2002. The distribution of the enigmatic reptile Vancleavea in the Upper Triassic Chinle Group of the western United States. New Mexico Museum of Natural History and Science Bulletin , 21:269-273.

Long, R.A. and Murry, P.A. 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. and Irmis, R.B. 2005. Advances in Late Triassic vertebrate paleontology based on new material from Petrified Forest National Park, Arizona. New Mexico Museum of Natural History and Science Bulletin , 29:45-58.

Polcyn, M.J., Winkler, D.A., Jacobs, L.L., and Newman, K. 2002. Fossil occurrences and structural disturbance in the Triassic Chinle Formation at North Stinking Springs Mountain near St. Johns, Arizona. New Mexico Museum of Natural History and Science Bulletin , 21:43-49.

New Triassic themed blog and another earliest dinosaur claim

I just recently became aware of this relatively new blog "The Life of Madygen" which has featured several posts on Triassic paleontology. Check it out. One recent post discusses purported sauropodomorph dinosaur footprints from Middle Triassic rocks near Bernberg Germany (also see this related article and my earlier post). If indeed attributable to dinosaurs, this find would represent the earliest occurrence of dinosaurs in the world; a claim which would need some accompanying body fossils to it back up, given the wide variety of Triassic critters that could hypothetically create a "dinosaur" track. One of the more outspoken critics of the claim seems to be Dr. Hartmut Haubold, an archosaur track specialist, who stated "It's ridiculous, it's as if someone found a 10-million-year-old stone and claimed it was a hand axe made by humans." "Dinosaurs didn't come into existence until a good 15 million years later" than these tracks. Haubold believes the trackmaker is Cheirotherium, which has been attributed to crocodile-line archosaurs such as "rauisuchians" (who do have body fossils preserved in Middle Triassic deposits).

Whereas I consider tracks to provide important information regarding the fossil record, especially information about the "living animal" that bones alone cannot preserve, I feel that claims such as these should only be made in concert with other lines of evidence, especially body fossils. I am reminded of a talk I saw a few years ago where it was stated that based on track evidence, the most common animal in the Late Triassic fauna of North America were sauropods. I found this claim quite perplexing given that not even a single bone of a sauropodomorph has ever been found in rocks of this age.