Enaliarctinae, a new group of extinct aquatic Carnivora

p. 203-284 : ill. ; 27 cm.Includes bibliographical references (p. 280-284)."The new genus and species Enaliarctos mealsi is based on two partial skulls and two natural endocranial casts discovered in the early Miocene Pyramid Hill Sand Member of the Jewett Sand at Pyramid Hill, Kern County, south-central California. The new mammalian subfamily Enaliarctinae is based on Enaliarctos mealsi. Enaliarctos mealsi was a medium-sized arctoid carnivore, a transitional species that departed in structure from terrestrial ursids (Hemicyoninae) and evolved in the direction of aquatic pinnipeds (Otariinae). Ursid features include presence and structure of upper and lower fourth premolars and of two molariform, quadrate-shaped upper molars; the development of sulcus cruciatus and the presence of an 'ursid lozenge'; and the morphology of the basicranium and middle ear. Features associated with aquatic adaptation include an enlarged narial chamber, reduced olfactory bulbs, wide snout, long and transversely arched palate, tendencies toward premolarization of the molars, narrow interorbital region, and enhanced brain circulation. A family Ursidae is recognized that includes primitive terrestrial ursids such as Cephalogale, Hemicyon, and Dinocyon in the subfamily Hemicyoninae. The Enaliarctinae is placed in Carnivora among the Otariidae near the Desmatophocinae. The Otariinae, specifically the Arctocephalini, might be descended from the Enaliarctinae. The phyletic lineage Hemicyoninae - Enaliarctinae - Otariinae emphasizes that the pinniped diphyly problem should be redefined to focus on the relationship of the Phocidae to even earlier Arctoidea. The Desmatophocinae might represent a third group independently derived from the middle-Tertiary adaptive radiation of Arctoidea. A lectotype for Neotherium mirum Kellogg, 1931 is chosen, and the species is included in the Enaliarctinae. The Pyramid Hill local fauna is named and characterized. The fauna comprises invertebrates and more than 39 species of Elasmobranchii, Teleostei, Chelonia, Aves, Squalodontidae (with a summary of northeast Pacific records), Delphinoidea, Mysticeti, Carnivora, Equidae (Anchitherium cf. A. agatensis), and Tayassuidae (Desmathyus sp.). The composition of the fauna indicates a warm-water, near-shore environment at the site of deposition. The Woody local fauna is named, characterized, and discussed. It is slightly higher stratigraphically in the same rock unit, 14 miles north of Pyramid Hill. We question Wilson's (1935) identifications of otariid pinnipeds from these rocks and doubt the validity of the 'phocid' record. The Pyramid Hill Sand can be assigned to the later Arikareean Land Mammal Age and to the Vaqueros Molluscan Stage, and it lies close to or includes the boundary between the Zemorrian and Saucesian Foraminiferal stages"--P. 205