Sloths are restricted to trees and are active mainly at night. Xenarthrans are chiefly solitary but may form small, loose associations. All have a good sense of smell, anteaters have poor eyesight and hearing, sloths have good vision but poor hearing, and armadillos have relatively good vision and hearing. Anteaters and some armadillos are basically insectivorous. Other armadillos are omnivorous, feeding on invertebrates, small vertebrates, some plant material, and carrion.
Sloths are herbivorous.
South American fossils are known from as far back as the Paleocene. Not until the middle Pliocene, a few million years ago, did some xenarthrans begin to invade North America. Anteaters and tree sloths moved no farther north than northern Mexico. The Pilosa sometimes were said to include an additional late Recent superfamily, the Mylodontoidea, and family, the Mylodontidae. The sloth remains consisted of several pieces of hide with long, reddish hair and studded with oblong dermal ossicles similar to those previously known from other species of Mylodon.