The link between dental microwear and feeding ecology in tree sloths and armadillos (Mammalia: Xenarthra)

The Xenarthra represents an enigmatic clade of placental mammals that includes living tree sloths, armadillos, and their extinct relatives, yet certain aspects of the biology of this group remains poorly understood. Here, we use scanning electron microscopy to test the hypothesis that orthodentine microwear patterns in extant xenarthrans are significantly different among different dietary groups. In a blind analysis, microwear patterns were quantified at a magnification of 500x by two independent observers for extant species from four dietary groups (carnivoreomnivores, folivores, frugivorefolivores, and insectivores). Independent observers recovered the same relative between-group differences in microwear patterns. Insectivores and folivores have a significantly lower numbers of scratches and greater scar widths than frugivorefolivores and carnivoreomnivores, yet we were neither able to statistically distinguish insectivores from folivores, nor differentiate frugivorefolivores from carnivoreomnivores. Nevertheless, a clear distinction exists between taxa from the same trophic level and habitat, which suggests that orthodentine microwear reflects niche partitioning and habitat more than diet among related forms. We suggest that bite force and chewing mechanics have a strong influence on the formation of orthodentine microwear, which may explain some of the observed overlap between distinct groups (e.g. frugivorefolivores versus carnivoreomnivores). This study serves as a positive step forwards in our understanding of the ecological role of living xenarthrans, and serves as a foundation for using orthodentine microwear to reconstruct palaeoecology in extinct ground sloths, glyptodonts, and pampatheres. (c) 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, , .