Bivalves from Carboniferous glacial deposits of western Argentina

Late Palaeozoic glaciation of Gondwana affected ecosystems and caused provincialism in the earth’s biota. Periglacial seas favored the origin of endemic genera and species, and remarkable differences exist with faunas of the Palaeoequatorial realm. Carboniferous glacimarine deposits are almost everywhere associated with theLevipustula levis “cold” fauna. These bio- and lithofacies are ubiquitous along the peri-Gondwana belt that stretches from western Argentina to eastern Australia, including central Patagonia and Antarctica. Both glacial sediments and theLevipustula levis Zone are assumed to date from the beginning of the Namurian to an indeterminated part of the early Westphalian. The bivalve fauna associated with the Carboniferous glacial deposits of western Argentina is described, including four new species:Promytilus grandis n. sp.,Leptodesma (Leiopteria) aredesi n. sp.,Oriocrassatella andina n. sp., andMyofossa calingastensis n. sp. Six insufficiently preserved species are left in open nomenclature:Leptodesma (Leiopteria) n. sp.,Euchondria n. sp.,Schizodus n. sp.,Promytilus sp.,Cypricardinia? sp., andStreblopteria? sp.; it proved even impossible to decide whether a badly damaged incomplete specimen belongs toMyonia orVacunella. Five other species, which are known from single specimens, are assigned tentatively to the generaPhestia, Atomodesma, Pyramus, Vacunella, andPleurophorella.