ˌ ̷ ̷ ̷ ̷ ̷ ̷ˈthirēə noun plural
Usage: capitalized
Etymology: New Latin, from Greek astrapo- (from astrapē lightning) + New Latin -theria; akin to Greek aster-, astēr star — more at star
: an order of extinct So. American ungulates that may have diverged from primitive notoungulates in the Paleocene, flourished in the Oligocene and Miocene, and were distinguished by large size with marked disproportion between the powerful forequarters and feebly developed hindquarters, cowlike incisors accompanied by immense persistently growing canines and huge molars, and probably an elephantine proboscis