Riostegotherium was an extinct genus of xenarthra from the late Paleocene of Brazil. It is known from fossil of armoured ossicles which are similar to the ossicles of the armour of morden armadillos that is obvious that in South American as far back as the late Paleocene armoured armadillos existed. Leg bones found in the area of probably came from Riostegotherium as well.