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

地懒是一种高度多样化的神秘哺乳动物(Xenarthra)，在美国新近纪分布广泛。与加勒比海、北美和南美洲的大量化石记录相比，墨西哥目前只报告了很少的地面树懒遗骸，主要是孤立的骨头，从未详细记录过，也没有对它们进行说明、骨学描述和分类评估。因此，尽管墨西哥走廊对于评估北美和南美洲地懒之间的古生物地理和古生态关系至关重要，但大多数墨西哥地懒的状况实际上仍然不得而知。在此，我们建议在全国大量新发现的基础上，对墨西哥更新世/全新世地懒记录进行调查和修订。我们的研究将包括所有诊断的地面树懒化石标本的详细骨学记录以及分类学和墓葬学评估。我们建议记录墨西哥地面树懒物种的分布模式，根据花粉和植物遗骸重建其环境的一些基本参数，以及对与地面树懒相关的大型食草动物组合进行半定量分析。我们计划评估与邻近的地面树懒有关的可能的分化、交换和隔离，评估与人类、食肉动物和食腐动物的互动，最后讨论地面树懒灭绝的原因。然而，这项研究的主要目的是建立关于墨西哥地懒的最完整的数据库，并结合古生物地理图，这两者都可以作为进一步研究的试点。

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.