Litopterna (from Ancient Greek: λῑτή πτέρνα "smooth heel") is an extinct order of South American native ungulates that lived from the Paleocene to the Pleistocene-Holocene around 62.5 million-3,500 years ago, and were also present in Antarctica during the Eocene.

[1] Adianthidae generally had small body masses, with members of the genus Adianthus estimated to weigh 7.4–20 kilograms (16–44 lb).

Members of the proterotheriid subfamily Megadolodinae are noted for having bunodont (rounded cusp) molar teeth, which is largely unique to litopterns among South American native ungulates.

[2] Litopterna, like other "South American native ungulates" is thought to have originated from groups of archaic "condylarths" that migrated from North America.

[1] Sequencing of the collagen proteome and mitochondrial genome of Macrauchenia has revealed that litopterns are true ungulates, sharing a common ancestor with Notoungulata, and with their closest living relatives being Perissodactyla (the group containing living equines, rhinoceros and tapirs) as part of the clade Panperissodactyla, with the split from Perissodactyla being estimated at around 66 million years ago.