Abstract

Anew trematopid amphibian, Acheloma dunni, is reported based on excellently preserved cranial and postcranial elements recovered from the Lower Permian fissure fill deposits of the Dolese Brothers Co. limestone quarry near Richards Spur, Oklahoma. The new taxon is characterized by lateral exposures of the palatine (l.e.p.) and ectopterygoid (l.e.e.), which are clearly visible externally and completely enclosed within the suborbital elements. This large, terrestrial carnivore may represent the top predator of the Richards Spur assemblage. A phylogenetic analysis including 12 taxa and 53 cranial characters yielded a single most parsimonious tree, placing Ach. dunni within the monophyletic Trematopidae as the sister taxon to Acheloma cumminsi. Furthermore, the analysis includes the enigmatic Ecolsonia and Actiobates within Trematopidae, forming a clade with the Upper Pennsylvanian Anconastes and the Lower Permian Tambachia. The study comprehensively analyses all valid and aberrant forms of Trematopidae.