A NEW GENUS OF SALAMANDER (PLETHODONTIDAE, DESMOGNATHINI) FROM THE GRAY FOSSIL SITE OF TENNESSEE

A maxilla and atlas recovered from the Gray Fossil Site (GFS) represent a new genus of basal desmognathine salamander closely aligned with the extant Phaeognathus hubrichti. Phaeognathus is a monotypic genus of plethodontid, or lungless, salamander endemic to southern Alabama and is unusual among the largely biphasic and stream-associated desmognathini (Phaeognathus + Desmognathus) due to their completely fossorial lifestyle, highly reduced limbs, elongate body (total length ~25 cm) and direct developing young. Molecular work indicates the placement of Phaeognathus as sister to Desmognathus, and suggests the genus represents the most ancient lineage in this clade. We infer the GFS salamander to be ecomorphologically similar to Phaeognathus hubrichti based on the shared presence of a spatulate ossification of the jugal ligament. The presence of a large fossorial desmognathine in Appalachia during the Neogene represents discovery of a currently unexploited ecological niche, as no fully fossorial plethodontids are known from this area today or from the fossil record of the region. There are currently no other fossil bearing locales dated prior to the Pleistocene that recover desmognathines, and as such, discovery of a basal member of this clade from the earliest Pliocene can help shed light on the evolution of this tribe’s unique cranial morphology, and the deeper-time evolutionary dynamics of plethodontid communities in the Appalachian highlands during the Neogene, a period of marked climactic changes and widespread plethodontid radiations.