QUATERNARY KARST GEOMORPHOLOGY AND MAMMALIAN PALEOBIOLOGY IN SEMIARID NORTHEASTERN BRAZIL

Limestone terrains in the Brazilian state of Bahia preserve abundant sedimentary and paleontological data for reconstructing Quaternary biotas. Included among the thousands of caves are the longest cave in the southern hemisphere (Toca da Boa Vista), which contains a rich and diverse fossil fauna. The presently semiarid climate contributed to the exceptional preservation of vertebrate fossils, including entire skeletons in minimally disturbed deposits. In this study we attempt to link the palaeoenvironmental profile of the karst geomorphology to the habitat evidence of the fossil taxa recovered from the same caves. We recognize that bias in the fossil record may be caused by the fossil emplacement process and the cave fossil assemblage may not mirror the fauna that once existed at the surface, but Toca da Boa Vista offers the best evidence of minimal bias. Travertine, water speleothem, and fossil mammal data consistently indicate a general late Quaternary context and a specific emphasis on the Last Glacial Maximum. The data further indicate that this region between Amazonia and the Atlantic Coastal Forest was wetter than the general pattern interpreted for other lowland areas of Brazil during the LGM. Extant mammals recovered include carnivores (jaguars, jaguarundis, ocelots), xenarthrans (giant anteaters, armadillos), rodents (cavies, pacas), artiodactyls (brockets, peccaries), and bats. Extinct taxa recovered include saber-toothed cats, Arctotherium, Nothrotherium, giant prehensile-tailed porcupines, giant ateline primates, a diverse ground sloth assemblage, and a variety of bats. The inclusion of very small and very large species in the cave deposits in Bahia provides what may be a rare example of a fossilized mammalian community. The abundant micromammal fauna provides a check against the limited ability to assess environmental conditions from big animals alone. The fauna as a whole is dominated by habitat generalists. The habitat specialist taxa that are found require more forest cover and wetter conditions than generally supposed for northeastern Brazil in the Last Glacial Maximum.