Taphonomic aspects of the Pleistocene vertebrate assemblage of Itaborai, state of Rio de Janeiro, southeastern Brazil

摘要

Pleistocene vertebrates from Itaborai Basin have not been taphonomically studied prior to this work, limiting the understanding of the deposition and preservation of the only Pleistocene vertebrate accumulation known for the state of Rio de Janeiro. In this work, the taphonomic signatures of the Pleistocene vertebrate assemblage of Itaborai are identified and interpreted in order to increase the knowledge about the formation of this fossil association and the paleoecology of the region of Rio de Janeiro during the late Pleistocene. Our analysis shows that the thanatocoenosis was exposed to the biostratinomic processes during a small time span; that it is parautochthonous; and experienced short transport distances by normal fluvial streams and floods. Subsequently, the fossiliferous horizon was quickly covered by the superjacent soil. Yet, the skeletal elements were fractured and deformed during the sedimentary compaction. The differential preservation of megamammal bones is associated to the bone resistance against those destructive processes and to the specific anatomical features. Comparison between Itaborai and other Brazilian Pleistocene vertebrate accumulations shows that the Itaborai fossil accumulation was less affected by taphonomic processes, although it is also a time-averaged fossil concentration. Finally, some of the taphonomic features indicate an arid paleoclimate.