A NEW PLIOCENE DOLPHIN (CETACEA: PONTOPORIIDAE), FROM THE LEE CREEK MINE, NORTH CAROLINA

摘要

With only a single extant species, Pontoporia blainvillei, Pon-toporiidae is a relict group that is presently restricted to Atlanticcoastal waters of Brazil, Uruguay, and Argentina (Crespo, 2002).The extinct diversity of this family is much greater, with at least 6named species, and possibly more if the long-snouted genusParapontoporia is included (see Barnes, 1985; Godfrey andBarnes, 2008). Extinct taxa are known from the east and westcoasts of South America (Burmeister, 1885; Muizon, 1984,1988a), the East Coast of North America (Morgan, 1994;Godfrey and Barnes, 2008), and the North Sea Basin of theEastern Atlantic (Lambert and Post, 2005; Pyenson and Hoch,2007). Both morphological (e.g. Muizon, 1988b; Geisler and San-ders, 2003) and molecular data (e.g. Cassens et al., 2000; Nikaidoet al., 2001) support the Amazonian River Dolphin Inia geoffren-sis as the closest extant taxon to Pontoporia; together these taxahave been placed in the Superfamily Inioidea. While the distribu-tions of extant taxa of Inioidea do not hint at the former widergeographic distribution of this Glade, several analyses (Nikaidoet al., 2001; Yan et al., 2005) support the Yangtze River dolphinas the sister-group to Inioidea. If this is the case, the far flungdistribution of these taxa, two of which are restricted to riverbasins, raises several important questions. Was the common an-cestor of Lipotes and Inioidea riverine or marine? Were ponto-poriids primitively riverine, and is the reduction in inioiddiversity related to the recent radiation of oceanic dolphins (i.e.Delphinidae)? Although answering these questions is beyond thescope of the present study, this paper will add to the growingextinct diversity of Pontoporiidae.