| Sumario: | Calyptogena gallardoi sp. nov. is described from eight articulated and 15 separated valves collected by dredge at similar to 760 in depth off the Bay of Concepcion, central Chile (similar to 36 degrees S). In general outline, C. gallardoi sp. nov. is close to C. pacifica and to a new species of Calyptogena from Peru, from which it differs in details of the shell shape and hinge margin. Bivalves of the genus Calyptogena are typical constituents of marine chemosynthesis-based communities, and are therefore indicators of reducing environments. In the area of occurrence, the presence of C gallardoi sp. nov. is related to methane seepage, associated in turn with the extensive gas-hydrate fields recently reported for the Chilean margin along 35 degrees S to 45 degrees S. Gas-saturated sediments as well as fragments of other chemosynthetic endosymbiont-containing clams of the families Vesicomyidae, Lucinidae, Thyasiridae and Solemyidae were also retrieved in the area. Calyptogena gallardoi sp. nov. is the first species of Calyptogena s.s. and the second species of the family Vesicomyidae so far described for the south-eastern Pacific area.
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