Therapedoidea (contains the families Therapedidae, Cerosidae, Choerocaballidae, Immanidae,
Aquatragulidae and Pasceridae)
Deinognathoidea (contains the families Deinognathidae, Jacanatheriidae, and Pelargidae)
Megacolloidea (contains the families Megacollidae and Diplonearidae)
Ungulascelidoidea (contains the family Ungulascelididae)
Most species are large, but as stated before, there are some small and delicate species. The trelatebrates are so named because both males and females have 3 vents, and no external testes. The reproductive tract is separate from the urinary tract as females only come into estrous one day out of the year, and there is no chance of the valuable sperm being lost, killed or voided in the urinary tract. In the Deinognathoids the teeth are serrated and actually peg-shaped. In the large species, like Deinognathus, the teeth are made for crushing, not necessarily tearing, though they are quite effective at tearing off chunks of meat. In the omnivorous species, as those in the Therapedoidea, the jaws are powerful, but the teeth are flat and made for grinding vegetation, with sharp incisors for ripping. The tail is long and thick and used to counterbalance the head, and also to help the animal keep it's balance when running, particularly for the bipeds.