Increased xenarthran diversity of the Great American Biotic Interchange: a new genus and species of ground sloth (Mammalia, Xenarthra, Megalonychidae) from the Hemphillian (late Miocene) of Jalisco, Mexico

Abstract

AbstractA new genus and species of megalonychid sloth,Zacatzontli tecolotlanensisn. gen. n. sp., is described from the late Hemphillian of Jalisco, Mexico. Comparison and analysis of the type specimen, a mandible, with other megalonychid sloths shows a closer relationship to South American taxa than those from North America or the Caribbean. This suggests that during the early stages of the Great American Biotic Interchange there were two separate dispersal events of megalonychid sloths—an earlier one represented byPliometanastesand the later one byZacatzontlin. gen. While the morphology of the spout ofZacatzontlimore closely resembles that ofMegalonyx, based on the current record,Zacatzontlidoes does not enter North America until after the evolution ofMegalonyxfromPliometanastes. The role of the northern neotropics in South America as a staging area for South American taxa that entered North America is discussed.