Investigation into the Paleobiology of Dasypus bellus Using Geometric Morphometrics and Variation of the Calcaneus

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The extinct taxon Dasypus bellus has long been considered identical to the extant Dasypus novemcinctus osteologically when disregarding allometric differences. In this study, we undertake a preliminary investigation into this extinct taxon and an extant relative D. novemcinctus, by comparing the calcanea of these two dasypodids. Clear osteological differences are observed including a mediolaterally-reduced facet region, an anteriorly-shortened calcaneal head, a reduced peroneal process, and a curved and dorsoventrally-shortened calcaneal foot in D. bellus. Such characters are not allometric and likely correlate to distinct behavioral differences. Specifically, we suggest that D. novemcinctus maintains a more fossorial lifestyle, while the larger D. bellus was likely more terrestrial, with potentially little digging behavior. Such lifestyle differences could not only explain the osteological differences present, but also why fossils of D. bellus have been recovered farther north than the present range of D. novemcinctus. Fossils of Dasypus may need to be re-evaluated to determine how these two taxa relate temporally and geographically, which may have further implications regarding some past interpretations and provide new details on the behavior and potential relationships between these (and other) xenarthrans.