Abstract

A newgenus, Austrogena, is established for a new species of vesicomyid bivalve (A. nerudai sp. nov.) described from sediments within the oxygen minimum zone off El Quisco, Chilean margin (similar to 33 degrees S) from similar to 340 m depth. The new genus is distinguished by a unique combination of conchological and anatomical features for vesicomyids, including the presence of an escutcheon, a lunular incision, an elongated 4-b tooth in the left valve, a subumbonal pit, both inner and outer pairs of demibranchs and the absence of pallial sinus and processes on the inner vulva of the inhalant siphon. In comparison with the majority of highly specialized pliocardiins, the alimentary gut of Austrogena is not straight and its middle gut changes direction twice. Molecular analysis, based on COI sequences, confirms that A. nerudai sp. nov. is not related to any other pliocardiin. So far, Austrogena gen. nov. is the only endemic vesicomyid genus in the south-eastern Pacific area and A. nerudai sp. nov. is the fourth species of vesicomyids reported from chemosynthetic communities of the Chilean margin. The description of the new genus further contributes to knowledge of biodiversity of chemosymbiotic assemblages in the south-eastern Pacific.