UC Santa Barbara

A nearly complete skull and fragmentary postcrania of a late Oligocene pinnipedimorph (SDNHM 146624) from the Pysht Formation of Clallam County, Washington, represent a new species of Pinnarctidion, a taxon previously known only from California and Oregon. This study provides a detailed anatomical description of SDNHM 146624 and offers the most comprehensive phylogenetic analysis of early-diverging pinnipedimorphs to date. Notable features of SDNHM 146624 include a posteriorly broad palate coupled with an anteriorly narrow rostrum, dorsoventrally deep zygomatic arches, and accessory cuspules on P3 and P4. The results of extensive comparisons indicate that SDNHM 146624 represents a new species of Pinnarctidion, P. iverseni, closely related to P. bishopi from California. Given the specimen’s superb preservation and relative completeness, SDNHM 146624 provides welcome new dental and cranial information for Pinnarctidion.