Ground sloths are a diverse group of extinct edentate (Superorder Xenarthra) mammals that are believed to be relatives of tree sloths and three-toed sloths. They may have died out as recently as 1550 in Hispaniola and Cuba (Nowak, 1999), but had long since been extinct on the mainland.
Four of the many identified species found in the United States consist of Harlan's Ground Sloth (Paramylodon harlani), Jefferson's Ground Sloth (Megalonyx jeffersonii), Laurillard's Ground Sloth (Eremotherium laurillardi), and the Shasta Ground Sloth (Nothrotheriops shastensis). All four were massive animals with large claws, and all are believed to have been herbivores.