(cohort Ferungulata, superorder Protoungulata)
An extinct order of S. American ungulates that appeared during the Eocene and flourished in the absence of herbivore competition or carnivore predation during the Oligocene and Miocene. The skull was short, the upper incisors were lost and the premaxillae much reduced, the lower incisors were present, the upper and lower canines were large and persistently growing, and the rearmost molars were large. A slit-like nasal opening on top of the skull suggests that astrapotherids (e.g. the Miocene Astrapotherium, which was the size of a rhinoceros) had elephant-like probosces. In contrast to the heavily built front legs, head, neck, and anterior part of the body, the spine, hindquarters, and hind legs were feeble. The feet were small, perhaps resting on pads, but unlike those of any other group. Possibly, therefore, the animals were amphibious.
Subjects: Zoology and Animal Sciences.