Thoatherium (meaning "active swift-beast") is an extinct genus of litoptern mammals from the Early Miocene of Argentina. Fossils of the genus have been found in the Santa Cruz Formation in Argentina.[1]

Temporal range: Early Miocene (Santacrucian)
~17.5–16.3 Ma
Thoatherium crepidatum.JPG
Thoatherium crepidatum skull
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Litopterna
Family: Proterotheriidae
Subfamily: Proterotheriinae
Genus: Thoatherium
Ameghino 1887
Type species
Thoatherium minusculum
  • T. bilobatum Ameghino 1904
  • T. crepidatum Ameghino 1891
  • T. karaikense Ameghino 1904
  • T. minusculum Ameghino 1887
  • T. rhabdodon Ameghino 1894
  • T. velatum Ameghino 1904
  • Merycodon Mercerat 1891
  • Rhagodon Mercerat 1891


Restoration of Thoatherium minusculum

With a length of 70 centimetres (2.3 ft), the gazelle-like Thoatherium was a small representative of the order Litopterna. Judging from its long legs, it was a fast runner. Thoatherium had remarkably reduced toes; only one horse-like hoof remained. Thoatherium even lacked splint bones, which are remnants of the second and fourth toe found in modern horses. Judging from its generalised, brachydont teeth, Thoatherium fed on soft leaves rather than on tough grasses.[2][3]


  1. ^ Thoatherium at
  2. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 247. ISBN 1-84028-152-9.
  3. ^ Darin A. Croft, Horned Armadillos and Rafting Monkeys: The Fascinating Fossil Mammals of South America, Indiana University Press, 29/08/2016