Late Quaternary fossil record of Myocastor Kerr, 1792 (Rodentia: Hystricognathi: Caviomorpha) from Brazil with taxonomical and environmental remarks

摘要

Myocastor Kerr, 1792 is a semi-aquatic caviomorph rodent that lives in southern South America. Pleistocene fossils of Myocastor are known from Argentina, Bolivia, Uruguay, and Brazil. This contribution is intended to clarify the taxonomic situation of the specimens of this taxon from the Brazilian Quaternary. The material was collected in late Quaternary localities from the states of Bahia, Minas Gerais, and Rio Grande do Sul. We assign these specimens to Myocastor coypus (Molina, 1782). Although some variation was seen, we do not consider it significant enough to include the fossil specimens in other extinct previously described taxa or in a new taxon. The modern original range of Myocastor encompasses only southern South America, but in the late Pleistocene/early Holocene, its distribution was displaced, at least to Bahia (～10°S), northeast Brazil. This fact could be related to the presence of more humid environments in the the late Pleistocene/early Holocene of this region in comparison with the modern days, where the Caatinga is predominant.