A NEW TAXONOMIC ARRANGEMENT FOR PALEORHINUS SCURRIENSIS LANGSTON 1949

The paraphyletic taxon ‘Paleorhinus’ is understood currently as a cosmopolitan group of phytosaurs known from the Late Triassic. There is no consensus regarding the number of species of ‘Paleorhinus;’ multiple species and genera were synonymized into a single genus or even a single species at various points in its published history. The taxonomy is confounded by historical descriptions that lack the benefit of comparisons to more recently collected specimens and an emphasis on plesiomorphic cranial morphology as diagnostic features. When included in a recent, explicitly cladistic phylogenetic analysis, the holotype of ‘Paleorhinus’ scurriensis (TTU P-00539) was recovered as the earliest-branching phytosaur with respect to other North American specimens previously referred to ‘Paleorhinus,’ and is generically distinct from Paleorhinus as exemplified by the genotype. ‘Paleorhinus’ scurriensis differs from all known phytosaurs in having the basitubera widely separated mediolaterally, a ridge present on the lateral surface of the jugal, a thickened shelf present along the posteroventral edge of an expanded pterygoid-quadrate wing, separated ‘septomaxillae’ that are excluded from the internarial septum, and a nasal swelling present posterior to the posterior borders of the nares. Non-phytosaurid phytosaurs are not limited to a single depositional basin or regional area, indicating that the early radiation of phytosaurs was not a diversification of a single basal clade but rather represents multiple cladogenetic events of Phytosauria potentially in the Early and Middle Triassic. The resulting biostratigraphic and biochronologic impacts of modified identifications of other non-phytosaurid phytosaur material indicate that much of our understanding of faunal dynamics in the early part of the Late Triassic may have been artificially compressed to a shorter time interval because of previous philosophies and methods of phytosaur identification.