A Primitive Seal (Mammalia: Phocidae) from Early Middle Miocene of Central Paratethys

Abstract

A well-preserved skull from the early middle Miocene (approximately 15 Ma) at Devinska Nova Ves (formerly Neudorf an der March), Slovakia, herein named <i>Devinophoca claytoni</i>, new genus and new species, is morphologically the closest common ancestor of all true seals. It shows a mixture of subfamilial characters. Features shared with Phocinae are the number of incisors and the lack of a strongly pronounced mastoid process. Characters similar to Monachinae are the shape of maxillae and the ratio between frontal and maxillary contacts of nasal bones. Characters shared with Cystophorinae are the ratio between interorbital width and mastoid width and (also shared with Phocinae) the ratio between length of auditory bullae and distance between them. Moreover, this skull has primitive features that are not known in any of the three subfamilies: Ml is triangular, with three cusps and three roots; in P2-P4 the larger posterior roots are clearly made up of two fused roots; the incisors form a curved line; the anterior palatal foramina are deep and oval; and the sagittal crest is very well developed. The traditional separation of the family Phocidae into the subfamilies Phocinae, Monachinae, and Cystophorinae has been intensively debated during the past 40 years and debate continues today, but we herein follow the traditional classification. The plesiomorphic D. <i>claytoni</i> is thus considered a sister taxon to the three extant subfamilies of Phocidae and is referred to a new subfamily, Devinophocinae. Because of its late age, D. claytoni cannot be ancestral to the more advanced phocids. Its primitive characters in combination with the characters it shares with the other subfamilies suggest, however, that it might approximate the common ancestral morphotype.