A description of the skull and postcrania ofHadrodelphis calvertenseKellogg 1966, and its position within the Kentriodontidae (Cetacea; Delphinoidea)

Abstract

ABSTRACT An associated skeleton of a large delphinoid from the Calvert Formation (lower middle Miocene) of Maryland is referable to Hadrodelphis calvertense Kellogg 1966, and includes the skull and periotic, as well as postcranial material. For the first time, a thorough description of this poorly known species is possible. Hadrodelphis is classified as a lophocetine kentriodontid based on features of its cranial vertex. Members of this subfamily possess rostro-caudally elongate nasals, and have a vertex which is transversely compressed, resulting in the maxillae becoming pinched or concave lateral to the vertex. Hadrodelphis calvertense exhibits a vertex which is extremely compressed and elevated, but the nasals are not inflated. Dental characters of H. calvertense and morphology of the periotic are essentially primitive. Although the family kentriodontidae appears to have been cosmopolitan in geographic distribution, species of Hadrodelphis have not been reported from the Pacific basin.