A new species of Aulacomya Mörch, 1853, and its paleobiogeographic significance

GENTA ITURRERÍA, S. F.; GRIFFIN, M.; PINEDA-SALGADO, G.; PARRAS, A.

Mar del Plata

Jornada; Reunión Anual de Comunicaciones de la APA; 2015

APA

The geographic range of extant species of Aulacomya is restricted to shelf environments in the southern hemisphere. A survey of fossil material referable to species belonging in this genus reveals that it already occurred in Pliocene (Waipipian and younger) rocks in New Zealand and in Pleistocene deposits along the Atlantic coast of Argentina, Uruguay and South Africa. The extant Aulacomya atra inhabits the Pacific coast of South America from Peru to Chile and up along the Atlantic coast to southern Brazil. It has also been recorded in the Malvinas and Kerguelen Islands and the along the Atlantic coast of Africa. The also extant Aulacomya maoriana lives along the coast of New Zealand. Aulacomya minuta n. sp. comes from the late Oligocene San Julián Formation in eastern Patagonia and the early Miocene Estancia 25 de Mayo Formation in western Santa Cruz. This is the oldest record of the genus, which appears to have originated in Patagonia and from there dispersed to other areas of the southern hemisphere. Such dispersion event(s), most likely involved rafting of juvenile or adult stages on drifting objects such as driftwood, volcanic material or on the attachment stems of algae such as the widespread southern hemisphere genus Macrocystis. The dispersion pattern is also related to the changing configuration of landmasses and seaways, and the consequent ocean current and climatechanges, taking place in the circumantarctic regions during the Cenozoic.