Revueltosaurus callenderi Hunt, 1989

Nesbitt, Sterling J., 2011, The Early Evolution Of Archosaurs: Relationships And The Origin Of Major Clades, Bulletin of the American Museum of Natural History 2011 (352), pp. 1-292 : 24

Revueltosaurus callenderi Hunt, 1989

( fig. 8H)

AGE: Middle-late Norian (Parker et al., 2005; most specimens from PEFO fall within 30 m of the Black Forest Bed which was radiometrically dated at 213 ± 1.7 Ma ( Riggs et al., 2003).

OCCURRENCE: Bull Canyon Formation, Dockum Group; Petrified Forest Member, Chinle Formation.

HOLOTYPE: NMMNH P-4957, a nearly complete premaxillary tooth.

REFERRED MATERIAL: PEFO 34561, essentially complete skeleton; PEFO 34269, nearly complete skeleton; see Parker et al. (2005) for other specimens.

REMARKS: The original description of Revueltosaurus was based on isolated teeth from the Upper Triassic deposits of the American Southwest ( Hunt, 1989; Padian, 1990). As described by Hunt (1989), followed by Heckert (2002), Revueltosaurus shares an uncanny resemblance to the teeth of early ornithischians. The similarity of teeth of Revueltosaurus to ornithischians led to the proliferation of the naming of isolated diagnosable teeth similar to those of ornithischians from other Triassic deposits ( Hunt and Lucas, 1994; Heckert, 2002). These isolated teeth formed the basis of our understanding of the early ornithischian record in North America and Europe. Parker et al. (2005) reported a partial skeleton referred to Revueltosaurus from the Petrified Forest Member of the Chinle Formation. They demonstrated that Revueltosaurus is a pseudosuchian, not a dinosaur. Consequently, Revueltosaurus illustrates the difficulty of assigning isolated teeth to a taxon; none of the ‘‘ornithischian-like’’ teeth from the Triassic of southwestern America can be confidently assigned to Ornithischia ( Irmis et al., 2007b) .

Much of the Revueltosaurus cranial and postcranial material originates from a monotypic bonebed. The specimens occur as isolated bones, complete associated specimens, or articulated skeletons. Thus, nearly the entire skeleton of Revueltosaurus is known. The phylogenetic position of the new, nearly complete specimens of Revueltosaurus have yet to be tested in a broad phylogenetic analysis of basal archosaurs. A full description of the skeleton is underway (Parker et al., in prep.).

KEY REFERENCES: Hunt, 1989; Heckert, 2002; Parker et al., 2005.