Ctenacanthiform sharks from the Permian Kaibab Formation, northern Arizona

A diverse assemblage of chondrichthyans has recently been recognised from the Permian (Late Leonardian) Kaibab Formation in and around Flagstaff, Arizona. Of this diverse assemblage, the ctenacanthiforms constitute seven tooth taxa of which three are new: Saivodus sp., Neosaivodus flagstaffensis gen. et sp. nov., Glikmanius occidentalis, Glikmanius myachkovensis, Heslerodus divergens, Kaibabvenator swiftae gen. et sp. nov. and Nanoskalme natans gen. et sp. nov. The range in tooth types suggests predator partitioning within these ctenacanths. Saivodus sp., Neosaivodus flagstaffensis gen. et sp. nov., H. divergens, G. occidentalis and G. myachkovensis had puncturing and grasping teeth adapted for securing smaller prey to be swallowed whole. Nanoskalme natans gen. et sp. nov. had teeth for grasping and cutting, perhaps an adaption for feeding or scavenging on larger organisms, whereas K. swiftae gen. et sp. nov. had large grasping and serrated cutting teeth for feeding on larger prey and was perhaps the apex predator of the Kaibab Sea. A cladistic analysis of the Ctenacanthiformes based on teeth suggests that in contrast to previous interpretations the family Ctenacanthidae may in fact be paraphyletic. We propose that the Ctenacanthiformes had a greater familiar diversity than currently recognised. The Kaibab assemblage is presently the most diverse ctenacanth assemblage for the global marine Permian.