Dissorophid diversity at the early Permian cave system near Richards Spur, Oklahoma, USA

The early Permian karst deposits near Richards Spur, Oklahoma, preserve a diverse assemblage of terrestrial dissorophoid temnospondyls in an upland environment. The dissorophids, an armored dissorophoid Glade, were previously represented only by two species of the eucacopine Cacops, Cacops morrisi and Cacops woehri, a genus also known from the lowland floodplains of the Texas red beds by the genotype C. aspidephorus. Here we report the first documented occurrences of two other dissorophid taxa at Richards Spur, Aspidosaurus and Dissorophus, identified on the basis of their distinctive osteoderms. Similar to Cacops, both taxa are also known from the Texas red beds and other lowland Permo-Carboniferous localities. Their documentation increases both the dissorophoid diversity at Richards Spur and the faunal overlap between the tetrapod assemblage at Richards Spur and the classic early Permian localities of North America. Additional cranial and postcranial material is referred to C. morrisi, to a previously reported indeterminate dissorophine, and to C. woehri, the knowledge of which is greatly expanded through this report. Analysis of several osteoderm morphotypes using neutron tomography reveals information that both strengthens taxonomic referrals (e.g., bifurcated ventral flange in Dissorophus) and reveals unexpected new insights into dissorophid osteoderm variation (ventral flange of the internal series in Cacops; presence of an internal series in Aspidosaurus). The extensive diversity of terrestrial dissorophoids at this site is unparalleled and furthers the interpretation of the assemblage as a unique early Permian paleocommunity produced by distinct environmental conditions.