A NEW GENUS OF MEGALONYCHID GROUND SLOTH (MAMMALIA, XENARTHRA) FROM THE LATE PLEISTOCENE OF QUINTANA ROO, MEXICO

A new genus and species of late Pleistocene megalonychid sloth, Nohochichak xibalbahkah, gen. et sp. nov., is described from Hoyo Negro, a chamber in the Sac Actun cave system, Quintana Roo, Mexico. Phylogenetic analysis indicates that this new sloth is most closely related to Meizonyx salvadorensis from the middle Pleistocene of El Salvador, and that these two genera in turn are the sister clade to Megistonyx and Ahytherium in South America and not the other North American megalonychids, Pliometanastes and Megalonyx. This new sloth indicates that the number of sloth taxa involved in the Great American Biotic Interchange is greater than previously understood, and that a significant part of the Interchange biodiversity, as represented by taxa confined to the semitropical and tropical portions of Central and North America, remains to be discovered.