West Antartica WANT Paleogene terrestrial biota: testing the biogeographical pattern of the final breack-up of Godwana

MARCELO REGUERO; ALEJANDRA ABELLO; TANIA DUTRA; ARI IGLESIAS; ADRIANA CANDELA; SERGIO MARENSSI

Abriendo Ventanas al Pasado, libro de Resúmenes II Simposio de Paleontología en Chile

Instituto Antártico Chileno-Centro de Estudios del Cuaternario y Antártida

Lugar: Punta Arenas; Año: 2012; p. 157 - 160

The thickest Late Cretaceous to lowermost Paleogene (Campanian to Ypresian) sedimentary succession in the world is exposed on southern Seymour Island (65° South) in the James Ross Basin, Antarctic Peninsula (Fig. 1). Paleogene terrestrial vertebrate fauna from Seymour Island exhibits high levels of species endemism, i.e., marsupials and meridiungulates, yet, for certain groups, is relatively species-poor (MacPhee et al. 2008). This fauna is also taxonomically imbalanced in that it is not typically ?South American? (Reguero and Marenssi 2010), as might be expected if most of its ancestors dispersed over a land bridge across the Antarctic Peninsula isthmus (Fig. 2) or used several intervening islands in a stepping-stone chain facilitated by past lower sea levels (Reguero et al. 2002). Although a few groups appear to be stranded relicts, resulting from West Antarctica?s shared plate tectonic history with other Gondwanan continents (Goin et al. 2006), for most clades current evidence indicates that the basal stocks arrived after the island, and the Antarctic Peninsula, were geographically isolated, thus refuting a vicariance model for these organisms. The close similarities and, in most cases, inferred sister-group relationships of a number of terrestrial vertebrate taxa recovered from Early Eocene deposits of Antarctic Peninsula, Australia, and South America