Paleoecological and paleobiogeographic significance of two new species of bivalves in the Paraná Formation (late Miocene) of Entre Ríos province, Argentina

PÉREZ, L. M.; GENTA ITURRERÍA, S. F.; GRIFFIN, M.

MALACOLOGIA

INST MALACOL

Lugar: Philadelphia; Año: 2010

0076-2997

ABSTRACT Two new species are described based on material from the Late Miocene Paraná Formation (Entre Ríos, Argentina), i.e., Polymesoda muravchiki nov. sp. and Erodona doellojuradoi nov. sp. The bearing rocks were deposited during the Entrerriense ingression that covered part of central-northern Argentina, reaching as far north as Bolivia, Paraguay and southern Brazil. The exposure from where the material was collected represents a rich parautochtonous assemblage - including also marine taxa - that has been assigned to the Late Miocene. Extant representatives of Polymesoda and Erodona are known to inhabit mostly brackish environments in the Caribbean region, the eastern Pacific coast of America, and South East Asia (in the case of Polymesoda), and the Atlantic coast of southern South America (Erodona). The presence of these bivalves in the Paraná Formation suggests that at least a marginal connection may have existed between a southern arm of the Amazonian Sea and the Paraná Sea during the Miocene. It is highly unlikely that these taxa could have migrated along the Atlantic coast of South America – contrarily to the case of the fully marine taxa – in view of their peculiar ecological requirements.