Pliocene notoungulates

Toxodontia is a suborder of the meridiungulate order Notoungulata. Most of the members of the five included families, including the largest notoungulates, share several dental, auditory and tarsal specializations. The group is named after Toxodon, the first example of the group to be discovered by science.

thumb|right|Xotodon sp. skull at the Museum für Naturkunde, Berlin

Hegetotheriidae is an extinct family of notoungulate mammals known from the Oligocene through the Pliocene of South America. The family underwent many sequential radiation events throughout the Cenozoic, which led to Hegetotheriids being among the most diverse of the Typotheria.

Mesotheriidae ("Middle Beasts") is an extinct family of notoungulate mammals known from the Oligocene through the Pleistocene of South America. Mesotheriids were small to medium-sized herbivorous mammals adapted for digging.