Early tetrapod jaws from the Late Devonian of Pennsylvania, USA

Abstract

Recent paleontological fieldwork in the Upper Devonian Catskill Formation at Red Hill in Clinton County, Pennsylvania, USA, has produced a diverse assemblage of vertebrate fossils including early tetrapods. The tetrapod Hynerpeton bassetti was described from the site in 1994 and a recently recognized partial lower jaw of that taxon is described here. Additionally, this paper describes a new Late Devonian tetrapod, Densignathus rowei new genus and species, based on a well-preserved lower jaw. This new taxon is characterized by dramatic widening of the jaw anterior of the adductor fossa, a pronounced twist in the orientation of ventral margin of the jaw, an uninterrupted exposure of Meckelian bone on the mesial surface, and weakly-developed radiating ornament on the lateral surface of the infradentaries. Although phylogenetic resolution within stem tetrapods is lacking, Densignathus rowei, n. gen. and sp., informs several topics including the sequence of character acquisition in the lower jaw, morphological diversity, and paleoecology of the earliest tetrapods.