DENTINE MICROWEAR IN XENARTHRA: IMPLICATIONS FOR PALEODIETARY RECONSTRUCTION

Dental microwear is a well-established method for analyzing paleodiet in extinct animals through direct comparison with extant taxa. However, previous research has focused predominately on food scar patterns in enamel. The question of whether microwear in dentine can indicate diet has not been addressed. This issue particularly affects xenarthran taxa (including modern sloths and armadillos), as their teeth are comprised solely of dentine. Quantitative and qualitative analyses of microwear patterns in extant xenarthran taxa (for which primary diet is known) will allow inference of textural composition of paleodiet in extinct xenarthrans (such as ground sloths, glyptodonts and pampatheres). Microwear features (i.e., number of scratches and pits; presence of cross scratches, hypercoarse scratches, gouges, and large pits) were analyzed in the orthodentine of upper teeth from over two hundred extant xenarthran individuals (Bradypodidae, Dasypodidae, Megalonychidae) via low-magnification (35X) stereomicroscopy. A database correlating dentine microwear patterns with known primary diet for each respective taxon was established. Canonical discriminant function analysis (DFA) was used to discriminate microwear variables in extant xenarthran individuals belonging to four dietary groups: carnivore-omnivores, folivores, frugivore-folivores, insectivores. DFA showed that folivores (Bradypodidae) are easily distinguished from frugivore-folivores (Megalonychidae), and both of these are distinct from carnivore-omnivore/insectivores (Dasypodidae). Insectivores and carnivore-omnivores are more difficult to distinguish from each other. Microwear patterns in several extinct xenarthran taxa (i.e., Megalonyx, Holmesina) were then analyzed and compared to this database to test the validity of dentine microwear in assessing paleodiet. Preliminary results show that fossil dentine microwear can yield paleodietary information. The results of this study are significant not only in determining the significance of dentine microwear features in interpreting paleodiet, but also in allowing future comparison of dentine microwear with previous accounts of enamel microwear in order to gain a broader understanding of the mechanics of food scarring on different dental tissues.