Toxodon is an extinct mammal of the late Pliocene and Pleistocene epochs about 2.6 million to 16,500 years ago. It was indigenous
to South America, and was probably the most common large-hoofed mammal in South America at the time of its existence. Charles
Darwin was one of the first to collect Toxodon fossils, after paying 18 pence for a T. platensis skull from a farmer in Uruguay.
Toxodontidae is an extinct family of notoungulate mammals known from the Oligocene through the Pleistocene of South America,
with one genus, Mixotoxodon, known from the Pleistocene of Central America. They somewhat resembled rhinoceroses, and had
teeth with high crowns and open roots, suggesting that they often fed on tough pampas grass.
Toxodonta is a suborder of the extinct mammalian order Notoungulata. The group is named after Toxodon, the first example of
the group to be discovered. The suborder includes the largest known notoungulates, members of the family Toxodontidae. Toxodontids
first appeared during the Oligocene in the form of Proadinotherium. Another well-known toxodontid is Nesodon, a medium-sized
Miocene toxodontid descended from Proadinotherium which had converted its second upper incisors into tusks.
Typotheria is a suborder of the extinct mammalian order Notoungulata and includes five families: Archaeopithecidae, Campanorcidae,
Interatheriidae, Mesotheriidae, and Oldfieldthomasiidae. Cifelli indicated that Typotheria would be paraphyletic if it excluded
members of the suborder Hegetotheria and he advocated inclusion of the hegetothere families Archaeohyracidae and Hegetotheriidae
in Typotheria.
Interatheriidae is an extinct family of notoungulate mammals from South America. Interatheriids are known from the Paleocene
or Eocene through the Miocene (McKenna and Bell, 1997).
