A New Species of Nyanzachoerus (Mammalia, Artiodactyla, Suidae, Tetraconodontinae) from the Upper Miocene Nakali Formation, Kenya

A new species of Nyanzachoerus (Mammalia, Artiodactyla, Suidae, Tetraconodontinae), Nyanzachoerus nakaliensis, is described on the basis of gnathodental specimens from the basal upper Miocene Nakali Formation (ca. 10 Ma) of central Kenya. Ny. nakaliensis is characterized by a lower crown height and relatively weaker furrows of the molars and proportionally larger P3-P4 compared to M3 among the species of the genus. It is the oldest and morphologically most primitive species of the genus. It shows close morphological similarities of the dentition with the Pliocene Asian tetraconodontine genus Sivachoerus, implying a possible closer phyletic relationship of Sivachoerus prior with Ny. nakaliensis rather than with Nyanzachoerus tulotos or Nyanzachoerus devauxi. This phyletic relationship implies a possibility that S. prior diverged from a stock of Ny. nakaliensis during the early late Miocene (Tortonian) in East Africa and then the lineage moved from East Africa to Asia. Finally, it should be stressed that there seems to be a problem of the paraphyly of the genus Nyanzachoerus.