† Astrapotheriidae † Eoastrapostylopidae † Trigonostylopidae Astrapotheria is an extinct order of South American[2] and Antarctic[3] hoofed mammals that existed from the late Paleocene to the Middle Miocene, 59 to 11.8 million years ago.

[2] Astrapotheres were large, rhinoceros-like animals and have been called one of the most bizarre orders of mammals with an enigmatic evolutionary history.

However, collagen and mitochondrial DNA sequence data analysed in 2015 places at least the notoungulates and litopterns firmly within Laurasiatheria, as a sister group to the perissodactyls.

[4] Postcranially, astrapotheres are relatively robust and more or less graviportal but have slender long bones, most notably in the hindlegs, suggesting they were amphibious.

[8] The most famous member of the order is undoubtedly Astrapotherium, a 3 m (9.8 ft) long elephant-like animal that had lost its upper incisors and developed ever-growing canine tusks.

Other astrapotheriids, such as the Casamayoran Scaglia and Albertogaudrya, were between a sheep and a tapir in size and already the largest South American mammals.