Revueltosaurus

Revueltosaurus Temporal range: Late Triassic, Norian PreЄ Є O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Node:	Suchia
Genus:	†Revueltosaurus Hunt, 1989
Species
†R. callenderi Hunt, 1989 (type) †R. olseni (Hunt & Lucas, 1994) †R. hunti Heckert, 2002
Synonyms
Krzyzanowskisaurus (Heckert, 2002) Pekinosaurus Hunt & Lucas, 1994

Revueltosaurus ("Revuelto lizard") is an extinct genus of suchian pseudosuchian from Late Triassic (Norian stage) deposits of New Mexico, Arizona and North Carolina, USA. Many specimens, mostly teeth, have been assigned to Revueltosaurus over the years. Currently, three species are included in this genus, all of which were thought to represnt monospecific genera of basal ornithischian dinosaurs.

Species

Revueltosaurus callenderi

R. callenderi was named by Adrian P. Hunt in 1989 and it is the type species of the genus. The generic name honors its type locality, Revuelto Creek, Quay County of New Mexico. Revuelto is derived from Spanish revolt, "revolution", in reference to the importance of the Late Triassic eriod for terrestrial vertebrate evolution. The specific name honours the director of the New Mexico Museum of Natural History Jonathan F. Callender. R. callenderi was originally described as a basal ornithischian on the basis of 32 teeth: the holotype NMMNH P-4957 a nearly complete premaxillary (incisiform) tooth, the paratypes (NMMNH P-4958-9, a nearly complete maxillary or dentary tooth crown with root and a nearly complete premaxillary tooth crown) and 28 referred specimens. All specimens were collected from the type locality, from the Bull Canyon Formation, dating to the Norian stage.

Later, other teeth were described by Padian (1990) and Hunt and Lucas (1994). Andrew B. Heckert (2002) redescribed the genus in detail and named a second species, R. hunti. Heckert listed the referred specimens CMNH PR1697-1699 originally described by Padian (1990) and the topotypes NMMNH P-4960, P-16573, P-33783-798. Four teeth were referred to aff. Revueltosaurus callenderi (NMMNH P-17362, P-17382 and P-17187). R. callenderi is known to date only from the Revueltian (early-mid Norian, the type locality dates back to the early Norian) of Bull Canyon Formation (Dockum Group, New Mexico) and the Painted Desert Member of the Petrified Forest Formation (Chinle Group, Arizona). Parker et al. (2005) described several partially complete skeletons of Revueltosaurus callenderi (PEFO 33787-95), including a nearly complete and a partial skulls, from the Revueltosaurus Quarry, Petrified Forest National Park. According to William Parker, "we have pretty much erased the record of Triassic ornithischian dinosaurs from North America, Europe and worldwide, except for South America." His co-author Randall Irmis said, "because the teeth look like those we know from herbivorous ornithischians, people assigned them to the dinosaurs. We think we've shown that you can't rely on the dentition to determine what is an early dinosaur, which casts doubt on all the ornithischians from the Triassic of North America". Other skeletons were discovered from the Painted Desert, including the nearly complete specimen PEFO 34561 which have been fully reconstructed recently.

Classification

It was originally described as an ornithischian dinosaur based on several discoveries of teeth, but was reclassified when a partial skeleton was discovered in 2004. Since all purported Triassic ornithischians are known only from teeth and jaw fragments (with the exceptions of Eocursor and Pisanosaurus), the discovery has challenged their validity.

References

• Sanders, Robert. June 24, 2005. Revueltosaurus skeleton unearthed at Petrified Forest upsets dinosaur tale. University of California Berkeley News. Retrieved March 15, 2006.