	Site Map \| FAQ in Daily Almanac for Feb 11, 2012
Skip Navigation Home Black History Month Atlas Encyclopedia Dictionary Thesaurus Features Quizzes Timelines Countries

Fact Monster Kid's reference,
games, quizzes

Editor's Favorites

| Share

Encyclopedia—rodent

Types of Rodents

The approximately 4,000 rodent species are divided on the basis of their anatomy into three well-defined groups, or suborders, and more than 30 families. The Sciuromorpha, or squirrellike rodents, include the various species of squirrel, chipmunk, marmot, woodchuck (or ground hog), prairie dog, gopher (or pocket gopher), pocket mouse, kangaroo rat, and beaver. The Myomorpha, or mouselike rodents, include a great variety of mouse and rat species, as well as species of hamster, lemming, vole, muskrat, gerbil, dormouse, and jerboa. This is the largest rodent group. The Hystricomorpha, or porcupinelike rodents, include the porcupine, capybara, nutria (or coypu), agouti, cavy (including the domestic guinea pig), mara, and chinchilla, as well as many species whose common names include the term rat (e.g., the South American bush rat).

Rabbits and hares were once classified as rodents because of their large, chisel-shaped incisors. However, they are quite distinct anatomically and have a long, separate evolutionary history; they are now classified in an order of their own, the Lagomorpha. Using DNA analyses as evidence, some scientists believe that the some other groups of rodents have descended from different ancestors and should thus be placed in orders of their own.

Sections in this article: