Triassic Ornithischian? Krzyzanowskisaurus hunti revisited.

http://www.azstarnet.com/news/local/article_d4138dc4-60a2-544c-8ba8-45ed550df2c2.html

The Arizona Daily Star (Tucson, AZ), published this story earlier on local fossil collector Stan Krzyzanowski. Those of you familiar with dinosaur taxonomy may recognize the name in regards to the Triassic tooth taxon Krzyzanowskisaurus hunti, to which the story alludes.

This taxon, known from only a handful of isolated teeth, was originally described as a new species of the putative ornithichian dinosaur Reveultosaurus by Heckert (2002). When it was subsequently discovered that the type species of Revueltosaurus, R. callenderi, actually represented a non-dinosaurian pseudosuchian archosaur (Parker et al. 2005), Heckert (2005) referred R. hunti to this new genus, Krzyzanowskisaurus. Heckert's (2005:77) support for this new referral is that the teeth of K. hunti "appear more derived than R. callenderi, and are in fact more 'typically' ornithischian than those of R. callenderi". By more 'typically' ornithischian Heckert (2005:78) is referring to the presence of a "pronounced bulge on the lingual surface", which he hypothesizes as being homologous with the 'cingulum' found in basal ornithischian teeth. However, there is no strong evidence for this homology and thus there are no apomorphies whatsoever to support the referral of K. hunti to Ornithischia (Irmis et al. 2007). Likewise, no phylogentic analysis exists to support the claim that this tooth morphology would be more derived. In fact co-occurring fossils from the St. Johns area actually support the original referral of these teeth to Revueltosaurus, thus I maintain that no material from North America currently exists that can be unambiguously referred to Ornithischia (Parker et al. 2005; Nesbitt et al. 2007; Irmis et al. 2007), and the reconstruction below is most likely erroneous (and apparently plagiarized from Greg Paul, see the copyright and read the comments below).



The Krzyzanowski bonebed is a potentially interesting vertebrate microsite from the Chinle Formation near St. Johns (similar to sites in the same area collected by Charles Camp in the late 1920s), but to date has only received limited coverage in publications (e.g., Heckert et al. 2004; Heckert et al. 2005), including a claim by these authors as to the presence of what would be the only sauropodomorph material from the Upper Triassic of North America (besides Greenland, which is physiogeographically considered part of that continent).

REFERENCES

Heckert, A.B. 2002. A revision of the upper Triassic ornithischian dinosaur Revueltosaurus, with a description of a new species. New Mexico Musuem of Natural History and Science Bulletin 21:253–267.

Heckert, A.B. 2005. Krzyzanowskisaurus, a new name for a probable ornithischian dinosaur from the upper Triassic Chinle Group, Arizona and New Mexico, USA. New Mexico Museum of Natural History and Science Bulletin 29: 77–83.
Heckert, A.B., Lucas, S.G., and A.P. Hunt. 2005. Triassic vertebrate fossils in Arizona. New Mexico Museum of Natural History and Science Bulletin 29:16-44.

Heckert, A. B., Rinehart, L. F., Krzyzanowski, S. E., Lucas, S. G., and S.K. Harris. 2004. The Krzyzanowski bonebed: an Upper Triassic (Adamanian: latest Carnian) vertebrate fauna and its implications for microvertebrate studies. New Mexico Geology 26:64.

Irmis, R.B., Parker, W.G., Nesbitt, S.J., and J. Liu. 2006. Early ornithischian dinosaurs: the Triassic record. Historical Biology 19:3-22.
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., Nesbitt, S.J., Martz, J.W., and L.S. Browne. 2005. The
Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. Proceedings of the Royal Society of London, B 272:963–969.
The image above is from the linked article.