Most of us are familiar with sloths, the bear-like animals that hang from trees, live life in the slow lane, take a month to digest a meal and poop just once a week. Their closest living relatives are anteaters and armadillos, and if that seems like an odd pairing, there's a reason why. Today, there are only two sloth species, but historically, there were dozens of them, including one with a bottle-nosed snout that ate ants and another that likely resembled the ancestors of modern armadillos.