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This article is about the extinct rhinoceros. For the bivalves, see Trigoniidae.
Temporal range: late Eocene[1]
Trigonias osborni NMNH.jpg
T. osborni
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Rhinocerotidae
Genus: Trigonias
Lucas, 1900
Type species
Trigonias osborni
  • T. osborni
  • T. wellsi
  • Procaenopus Figgins, 1934[3]

Trigonias is an extinct genus of rhinoceros from the late Eocene (Chadronian) some 35 million years ago of North America (Prothero, 2005).

Restoration by Jay Matternes

It is the oldest rhino of which is still alive. Trigonias was about 2.1 m (7 ft) long and, despite lacking horns, looked a lot like modern rhinos. Its front legs had five toes (as contrasted with three in modern rhinos), the fifth of which was vestigal.[4]

A specimen of T. osborni was estimated to have a weight of about 391.4 kg (862.9 lbs).[5]


  1. ^ Prothero, 2005, p. 184.
  2. ^ Prothero, 2005, pp. 35-37.
  3. ^ Prothero, 2005, p. 35.
  4. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 264. ISBN 1-84028-152-9. 
  5. ^


  • Prothero, Donald R. 2005. The Evolution of North American Rhinoceroses. Cambridge University Press, Cambridge, 218 pp. ISBN 0-521-83240-3