The mammalian fauna of Abismo Iguatemi, southeastern Brazil

Abstract

The Quaternary vertebrate fauna record of South America is characterized by the predominance of mammals, and the study of cave deposits can provide important information on their diversity and distribution. In Brazil, cave deposits have preserved remarkable fossil remains, including both large and small vertebrates, although the former have been the focus of most paleontological works. The fossils studied here came from Abismo Iguatemi, a karstic fissure located in the municipality of Apiaí, upper Ribeira River valley, São Paulo, Brazil. Blocks of sediment collected from its floor yielded a large sample of micro-remains, mainly composed of fragmentary small vertebrate specimens. Taphonomic parameters suggest that the fossil elements entered the cave either by entrapment or transported by rain runoff, as partially decayed carcasses or isolated elements. A total of 35 taxa were recorded in Abismo Iguatemi, four of which are extinct. The number of identified specimens per taxon (NISP index) is the best estimator of number of individuals at the burial site. The comparison of this fauna to that of other Quaternary deposits and to the present biodiversity of different areas reveals low similarity. The identification of fossil organisms with different ecological requirements (extinct savannah organisms and extant dense-forest organisms) suggests the existence of time averaging and may reflect environmental changes in the vicinity of the cave during the late Pleistocene and Holocene.