High Quality Content by WIKIPEDIA articles! The superorder Xenarthra is a group of placental mammals (infraclass Eutheria), existent today only in the Americas and represented by anteaters, tree sloths, and armadillos. The origins of the order can be traced back as far as the Paleogene (about 60-65 Ma, shortly after the Mesozoic) in South America . Xenarthrans developed and diversified extensively in South America during its long period of isolation, invaded the Antilles by the early Miocene, and then spread to Central and North America starting about nine million years ago, as part of the Great American Interchange . Nearly all of the formerly abundant megafaunal xenarthrans, such as ground sloths, glyptodonts, and pampatheres went extinct at the end of the Pleistocene.