Abstract
Originally identified as an ornithischian dinosaur, Crosbysaurus harrisae has been found in New Mexico, Arizona, and its type locality in Texas, as well as in North Carolina. The genus has been reassessed by other workers in light of reinterpretations about the postcrania of another putative Triassic ornithischian, Revueltosaurus. The understanding of Triassic dental faunas has become more complicated by the extreme convergence between pseudosuchian archosaurs and ornithischian dinosaur dental morphologies. We report here on a new specimen of Crosbysaurus (MNA V10666) from the Chinle Formation at Comb Ridge in southeastern Utah. This new specimen is assigned to Crosbysaurus sp. on the basis of the unique compound posterior denticles, labiolingual width, and curvature. While MNA V10666 does not help resolve the affinities of Crosbysaurus, it does represent the extension of the geographic range of this taxon for approximately 250 kilometers. This is the first record of the genus Crosbysaurus in Utah and as such it represents the northernmost known record of this taxon. This indicates that Crosbysaurus was not limited to the southern area of the Chinle/Dockum deposition but instead was widespread across the Late Triassic paleoriver systems of western Pangea. The reported specimen was found in close association with a typical Late Triassic Chinle fauna, including phytosaurs, metoposaurs, and dinosauromorphs.
Highlights
Crosbysaurus harrisae was first described by Heckert (2004) the assumption was that it, like the better-known Revueltosaurus, was an ornithischian dinosaur
(2005) with the discovery of the postcrania of Revueltosaurus from the Petrified Forest of Arizona. Did this revise how Revueltosaurus was seen but it called into question the systematics of all purported ornithischian dinosaurs from North America (Irmis et al, 2007; see Nesbitt et al, 2007)
Reveueltosaurus is known from non-dental remains (Parker et al 2005) and the tooth variation documented in the premaxilla, maxilla, and dentary do not match any teeth reported as Crosbysaurus (Irmis et al, 2007). This holds true for MNA V10666 as well; there appears to be no place in the dentition of Revueltosaurus for a tooth with the morphology of the described specimen
Summary
Crosbysaurus harrisae was first described by Heckert (2004) the assumption was that it, like the better-known Revueltosaurus, was an ornithischian dinosaur. Several purported ornithischian taxa were named upon the discovery of isolated teeth, leading several authors to suggest that herbivorous dinosaurs were widespread across Pangea (Hunt and Lucas, 1994; Heckert, 2002, 2004, 2005). This scenario contrasted sharply with previous views on ornithischian diversity and stood in sharp contrast with the non-dental fossil record of ornithischians outside of the southern hemisphere. (2005) with the discovery of the postcrania of Revueltosaurus from the Petrified Forest of Arizona Did this revise how Revueltosaurus was seen but it called into question the systematics of all purported ornithischian dinosaurs from North America (Irmis et al, 2007; see Nesbitt et al, 2007).
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