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Temporal range: (Eocene?) Oligocene to Miocene
Metamynodon skeleton.jpg
Metamynodon planifrons skeleton
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Amynodontidae
Genus: Metamynodon
Scott & Osborn, 1887
Type species
Metamynodon planifrons
  • M. planifrons
  • M. chadronensis
  • †?M. mckinneyi

Metamynodon is an extinct genus of amynodont perissodactyls whose known species lived in North America (White River Fauna) and Eurasia during the early Oligocene to the Miocene, although the questionable inclusion of M. mckinneyi could extend their range back in time,[1] to the Middle Eocene. The various species were large, displaying a suit of semiaquatic adaptations similar to those of the modern hippopotamus despite their closer affinities with rhinoceroses.


Restoration by Charles R. Knight
Restoration by Heinrich Harder

Metamynodon planifrons, the largest species, was about 4 metres (13 ft) in body length with a weight up to 1.99 tons, and, although it was distantly related to the modern rhinoceros, looked more like a hippopotamus.[2] Its front legs had four toes instead of the three found in modern rhinos. Although it was a herbivore (as indicated by its teeth), its skull had a bony ridge typically associated with carnivorous mammals. It probably fed on tough plant material, and the jaw muscles were attached to this ridge. Metamynodon would have used its enlarged canines to search for food in river banks, and may also have had highly flexible lips. Its eyes were placed high on the skull, meaning that it would have been able to see while almost fully submerged, much like a hippopotamus or crocodile.[3]


  1. ^ Wall, William P. (1989). "The phylogenetic history and adaptive radiation of the Amynodontidae". In Prothero, Donald R; Schoch, Robert M. The Evolution of perissodactyls. Oxford University Press. ISBN 9780195060393. 
  2. ^
  3. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 264. ISBN 1-84028-152-9.