There are no Known Aetosaur Fossils from Madagascar!

I happened to click on the Wikipedia page for aetosaurs today. It is really shaping up as someone (or maybe a few people) is putting a lot of work into it. A few errors here and there and a couple taxonomic issues that will be addressed in some future publications (not all by me). However, the most glaring thing that caught my eye was location column for Desmatosuchus lists Madagascar (Isalo Group) as a unit containing fossils of Desmatosuchus. This is an occurrence I addressed in my M.S. thesis (Parker, 2003) and in my 2008 paper on the genus Desmatosuchus. It all stems from a problem in assigning a geological age to a fossil bearing horizon in the upper part of the Isalo II (part of the Isalo Group; Burmeister, 2000; Burmeister et al., 2006). This horizon includes fish fossils, as well as the remains of dinosaurs (sauropod, theropod) and other archosaurs, including teeth that are superficially similar to those of phytosaurs and a handful of osteoderms that belong to some type of pseudosuchian (see photo below from Burmeister, 2000).

Kurtis Burmeister first approached me in the late 1990s asking my opinion if these osteoderms could be from aetosaurs. I though the resemblance was purely superficial and despite he presence of an anterior bar and pitted ornamantation, the overall morphology and the lateral sutures were not typical of aetosaurs.  In his thesis, he suggested they could be crocodyliform (pers. comm. from Mike Parrish), but preliminarily assigned them to the Aetosauria and noted a possible assignment to Desmatosuchus. This identification was based on showing the osteoderms to another aetosaur "expert" (Burmeister, pers. comm.).

A few years later I was approached again by another member of the research team who showed me the specimens again.  This time I was with a small group of Triassic workers and coincidently we had a crocodyliform specialist with us as well.  We all agreed that they were definitely not Desmatosuchus, not aetosaurian, and most likely a crocodyliform. In a subsequent publication (Burmeister et al., 2006) they are refered to an indeterminate crocodylotarsian (pseudosuchian) and the superficial resemblance to aetosaurs is discussed, although the authors note the osteoderms probably represent a goniopholidid crocodyliform and that the horizon is probably Early Jurassic in age. Parker (2008) argued that they were not aetosaurian and possessed characters found in mesoeucrocodylians.

Despite all of this ambiguity, these specimens were explicitly assigned to the aetosaur Dematosuchus haplocerus by Lucas et al. (2003) and used to provide an Adamanian (late Carnian) age for these beds. This identification and correlation was followed by Lucas (2010).  Discussions with colleagues and the current Wikipedia entry for aetosaurs demonstrates that the identification of these specimens as aetosaurian is still misunderstood.  For the 4th time (and hopefully the last) I would like to propose my opinion (based on two personal observations of the material and the figure above) that these are not aetosaur plates and most certainly not referable to Desmatosuchus. The ornament is too deep and irregular, furhtermore, if these are fragments of paramedian plates then the ornament would be too large.  Finally, the sutural edges are completely different than anything found in aetosaurs, and certainly does not represent the "tongue-and-groove" articular surface found in desmatosuchines. There currently is no evidence for aetosaurs in the Isalo II and the age of the upper beds is most likely Jurassic (Burmeister et al., 2006; Parker, 2008) and not Adamanian in age (contra Lucas, 2010).

REFERENCES

Burmeister, K.C., 2000, Paleogeographic and biostratigraphic implications of new early Mesozoic terrestrial vertebrate fossils from the Poamay site: central Morondava Basin, Madagascar [M.A. thesis]: Santa Barbara, University of California, 109 p.

Burmeister, K.C., J.J. Flynn, J.M. Parrish, and A.R. Wyss. 2006. Paleogeographic and biostratigraphic implications of new early Mesozoic vertebrates from Poamay, central Morondava Basin, Madagascar. New Mexico Museum of Natural History Science Bulletin 37:457–475.

Lucas, S.G. 2010. The Triassic timescale based on nonmarine tetrapod biostratigraphy and biochronology; pp. 447-500 in  Lucas, S. G. (ed.) The Triassic Timescale. Geological Society, London, Special Publications, 334.

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

Parker, W.G. 2003. Description of a new specimen of Desmatosuchus haplocerus from the Late Triassic of Northern Arizona. M.S. thesis. Northern Arizona University, Flagstaff, AZ.

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. 

"Moon Rock" is Petrified Wood

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




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

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

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

---Sidney Ash"

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

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

And this is amusing as well:

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

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

REFERENCES

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

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

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.