<i>Simocetus rayi</i> (Odontoceti: Simocetidae, New Family): A Bizarre New Archaic Oligocene Dolphin from the Eastern North Pacific

Abstract

<i>Simocetus rayi</i> (new genus, new species) is based upon a skull and mandible of a small archaic dolphin (Cetacea: Odontoceti) from the upper Oligocene Alsea Formation of Oregon, bordering the northeast Pacific. The species shows many primitive features reminiscent of the archaic odontocete family Agorophiidae: the cheek teeth appear nonpolydont, the nares and premaxillary sac fossae lie anteriorly, the orbit and facial fossa are elevated above the level of the rostrum, the ascending processes of premaxillae are narrow and long, the supraorbital processes of the maxillae are narrow, the intertemporal constriction is prominent, and the pterygoid sinus fossae are restricted to the basicranium. These features are consistent with a basal position among the odontocetes, but they do not justify placement in the paraphyletic- and probably polyphyletic-grade family Agorophiidae. <i>Simocetus rayi</i> shows some unusual autapomorphies (toothless premaxillae, anterior of rostrum and mandible downtumed) that exclude it from described taxa of odontocetes, and for this reason it is placed in a new and currently monotypic family, Simocetidae. Broader relationships are uncertain; some cranial features hint at affinities with Eurhinodelphinidae. For now, <i>S. rayi </i>is regarded as a specialized archaic odon-tocete that lies sternward (more basal) to all extant groups of Odontoceti (namely, Physeteroidea, Ziphiidae, Platanistoidea, and Delphinida). <i>Simocetus rayi </i>was perhaps a bottom feeder that preyed through suction feeding on soft-bodied invertebrates. The inferred presence of nasal turbinals and a vomeronasal organ contrasts with the situation in living odontocetes. Features of the face and basicranium point to echolocation abilities comparable to those of extant Odontoceti. <i>Simocetus rayi</i> and other contemporaneous archaic odontocetes from Oregon and Washington indicate that odontocetes were taxonomically and ecologically diverse by the late Oligocene.