A New Megalonychid Sloth From the Late Wisconsinan of the Dominican Republic

—An unusually well preserved skull, mandible, and indisputably associated post-cranial elements of new sloth, Acratocnus (Miocnus), were recovered from a cave in Jaragua National Park, Dominican Republic. The animal died lying in a rimstone pool and was rapidly coated with a thin calcite patina. We have documented a late Wisconsinan age for this specimen by inorganic C radiometric dating of the patina, with supporting data on the carbon systematics of the speleothems in this cave. This sloth is described as a new species on the basis of the distinctive morphology and relative size of cranial and mandibular features. We consider the close relationship between Acratocnus of the Dominican Republic and Puerto Rico to constitute clear evidence for late Tertiary inter-island dispersal of this lineage, congruent with similar evidence from other West Indian terrestrial mammal orders.