Captorhinid reptiles from the Early Permian of New Mexico, with description of a new genus and species

Abstract

A new genus and species of single-tooth-rowed captorhinid, Rhiodenticulatus heatoni, is based on two skulls and partial postcranial skeletons collected from the Lower Permian Cutler Formation near Arroyo de Agua, north-central New Mexico. A cladistic analysis ofits relationships to other single-tooth-rowed captorhinids suggests that it is a primitive sister taxon to Labidosaurus and Eocaptorhinus. The dentition of R. heatoni, however, exhibits several unique derived features which are interpreted as representing an adaptation to a specialized diet. Puercosaurus obtiisidens Williston, 1916, the only previously described captorhinid from New Mexico, is declared a nomen dubium because the holotypic left dentary is indeterminate, and there is no basis for accepting that it and the two poorly preserved captorhinid skulls found at a different locality and referred to the species by Williston (1916) are conspecific. Additional captorhinid remains have been collected recently from the Lower Permian Cutler, Abo, and Sangre de Cristo formations at widely scattered localities in central and northern New Mexico. Though these specimens, as well as the skulls referred to ^‘‘Puercosaurus obtusidens,"’’ are too poorly preserved to be assigned to existing or new taxa, they do indicate that the Captorhinidae was diverse and widely distributed in the Lower Permian of New Mexico.