Mexican fossil ground sloths, a case study for Late Pleistocene megafaunal turnover in the Mexican Corridor

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Ground sloths are a highly diverse group of enigmatic mammals (Xenarthra) with a wide Neogene distribution in America. In contrast to the extensive fossil record from the Caribbean, North- and South America, only few ground sloth remains, mainly isolated bones, are presently reported from Mexico, which have never been documented in detail, nor were they illustrated or osteologically described and taxonomically evaluated. Therefore, the status of most Mexican ground sloths remains virtually unknown, even though the Mexican Corridor is essential for an evaluation of the palaeobiogeographic and palaeoecological relationships between North- and South American ground sloths. Here we propose to investigate and revise the Pleistocene/Holocene ground sloth record of Mexico based on abundant new discoveries throughout the country. Our research will include a detailed osteological documentation of all diagnostic fossil ground sloth specimens as well as a taxonomic and taphonomic evaluation We propose to document the distribution pattern of ground sloth species in Mexico, reconstruct some essential parameters of their environment based on pollen and plant remains as well as a semi-quantitative analysis of the mega-herbivore assemblage associated with ground sloths. We plan to evaluate possible divergence, interchange and isolation with respect to neighboring ground sloth regimes, evaluate the interactions with humans, carnivores and scavengers and finally discuss reasons for the extinction of ground sloths. The main objective of this study, however, is to erect the most complete database on Mexican ground sloths combined with a palaeobiogeographical map that both may serve as a pilot for further studies.