Résumé
Extinct terrestrial sloths are common elements of the late Cenozoic South
American fossil record. Among them, Mylodontinae species were particularly
abundant in the Americas throughout the Pleistocene epoch, and their
anatomy is relatively well known. In contrast, less information is
available from the Neogene record and particularly from localities at low
latitudes, with an additional and considerable bias in favor of
craniodental rather than postcranial remains. In this contribution, we
provide comparative descriptions of several postcranial bony elements
ascribed to Simomylodon uccasamamensis, a moderate-sized extinct
mylodontine from the Andean Altiplano. This species was particularly
abundant during latest Miocene–late Pliocene times in the high altitudes
of the Andean Cordillera, and so far represents the best known mylodontine
from the Neogene of South America. Its anatomy is compared with that of
several extinct terrestrial sloths, with the aim of using the observed
morphologies to elucidate taxonomy, phylogeny, and locomotion. From a
morphofunctional perspective, the postcranium of S. uccasamamensis is
consistent with that of a terrestrial graviportal quadruped, with moderate
climbing and digging capabilities.