Freshwater occurrence of the extinct dolphin Parapontoporia (Cetacea: Lipotidae) from the upper Pliocene nonmarine Tulare Formation of California

Abstract

The diminutive, extinct longirostrine dolphin Parapontoporia is one of the most abundantly represented late Neogene odontocetes from the eastern North Pacific and is widely known from numerous marine strata of late Miocene and Pliocene age in California, Baja California and possibly Japan. Parapontoporia has been identified as the sister taxon of the recently extinct Chinese river dolphin (Lipotes vexillifer); unlike Lipotes, which exclusively inhabited freshwater, the depositional context of Parapontoporia suggests it was marine. A newly identified petrosal of Parapontoporia sp. was preserved alongside terrestrial vertebrates in the nonmarine Tulare Formation (upper Pliocene to Pleistocene, 2.2-0.6 Ma), California, which was deposited under lacustrine and fluviodeltaic conditions. Abundantly preserved freshwater molluscs and rare marine taxa suggest predominantly freshwater settings with intermittent periods of estuarine conditions. This occurrence of Parapontoporia indicates its presence in the San Joaquin basin after the retreat of the inland sea and suggests that this extinct odontocete may have been freshwater tolerant and an inhabitant of marine and freshwater settings, heralding the exclusively freshwater existence of its Recent sister taxon Lipotes vexillifer.