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Temporal range: Early Eocene–Early Oligocene
Ischyromys skeleton, Smithsonian National Museum of Natural History
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Rodentia
Suborder: Sciurognathi
Family: Ischyromyidae
Genus: Ischyromys
Leidy, 1856
  • I. typus (type)
  • I. blacki
  • I. douglassi
  • I. junctus
  • I. veterior

Ischyromys is an extinct genus of rodent from North America.


The 60 cm (2 ft) long creature is one of the oldest rodents known. It resembled a mouse and already had characteristic rodent incisors. Ischyromys's hind legs were longer than the forelegs, which could be used for other means than walking. Unlike most other mammals of its time, Ischyromys was probably arboreal (along with its relative Paramys). It was a well-adapted climber that gradually beat out competition from rodent-like arboreal plesiadapiform primates.[1]


  1. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 283. ISBN 1-84028-152-9.