Paenungulata is a taxon that groups some remarkable mammals, including three orders that are extant: Proboscidea (including elephants), Sirenia (sea cows, including dugongs and manatees), and Hyracoidea (hyraxes, such as the African Rock Hyrax, Procavia habessinica). At least two more orders are known only as fossils, namely Embrithopoda and Desmostylia. Both of these extinct orders were as unique in their ways as the surviving orders. Embrithopods were rhinoceros-like herbivorous mammals with plantigrade feet, and desmostylians were hippopotamus-like amphibious animals. Their walking posture and diet have been the subject of speculation, but tooth wear indicates that desmostylians browsed on terrestrial plants and had a posture similar to other large hoofed mammals.
Of the five orders, hyraxes are the most basal, followed by embrithopods; the remaining orders sirenians, desmostylians and elephants are more closely interrelated. These latter three are grouped as the Tethytheria, because it is believed that their common ancestors lived on the shores of the prehistoric Tethys Sea. Although morphological evidence continues to support the position of paenungulates with the ungulates, the molecular evidence suggests that Paenungulata is part of the cohort Afrotheria, an ancient assemblage of mainly African mammals of great diversity. The other members of this cohort are the orders Afrosoricida (tenrecs and golden moles), Macroscelidea (elephant shrews) and Tubulidentata (aardvarks).