rodent

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rodent

rodent, member of the mammalian order Rodentia, characterized by front teeth adapted for gnawing and cheek teeth adapted for chewing. The Rodentia is by far the largest mammalian order; nearly half of all mammal species are rodents. They are worldwide in distribution and are found in almost every terrestrial and freshwater habitat, from the shores of the Arctic Ocean to the hottest deserts. They are variously adapted for running, jumping, climbing, burrowing, swimming, and gliding. Many of them have dexterous forepaws, which they use as hands while sitting on their haunches in a position characteristic of many rodents. The great majority are under a few inches in length; the largest, the capybara, is about 4 ft (120 cm) long and 20 in. (50 cm) high at the shoulder.

Characteristics of Rodents

Rodents have enlarged, chisel-shaped upper and lower front incisors that grow throughout their lives. These have hard enamel on the front surface and soft dentine on the back surface, so that unequal wear keeps the chisel edge sharp. There is a gap between the front teeth and the cheek teeth. When the lower jaw is in a forward position, for gnawing, the upper and lower incisors are in contact but the upper and lower cheek teeth are not; thus, wear on the cheek teeth is avoided. The cheeks are drawn in behind the incisors when the animal is gnawing, so that bits of hard material cannot be swallowed. When the lower jaw is pulled back into the chewing position, only the cheek teeth make contact.

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.

See also mountain beaver, ground squirrel, flying squirrel, pack rat, bandicoot rat, and jumping mouse.

Bibliography

See Sir J. R. Ellerman, The Families and Genera of Living Rodents (2 vol., 1940, repr. 1965); B. S. Vindgradov and A. I. Argiropulo, Key to Rodents (tr. 1968).

The Columbia Electronic Encyclopedia™ Copyright © 2022, Columbia University Press. Licensed from Columbia University Press. All rights reserved.

What does it mean when you dream about a rodent?

Gophers, rats, mice, and the like are a constant source of irritation and often spread disease, thus requiring extermination. Rodents in a dream may represent issues that are pestering the dreamer and perhaps confounding the dreamer as to how to dispose of them. (See also Mouse, Rat).

The Dream Encyclopedia, Second Edition © 2009 Visible Ink Press®. All rights reserved.

rodent

[′rōd·ənt]
(vertebrate zoology)
The common name for members of the order Rodentia.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

rodent

a. any of the relatively small placental mammals that constitute the order Rodentia, having constantly growing incisor teeth specialized for gnawing. The group includes porcupines, rats, mice, squirrels, marmots, etc.
b. (as modifier): rodent characteristics
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Accordingly, pursuant to 42 CFR 71.32(b), CDC is implementing an immediate embargo on the importation of all rodents from Africa (Order Rodentia).
The Myocastor genus belongs to the mammalian Order Rodentia based on morphological features common to the group, particularly dental features (Nowak 1991).
And here are 20 more squirm-making facts about Genus Rattus (family Muridae, order Rodentia)...
The biochemical phylogeny of guinea-pigs and gundis, and the paraphyly of the order rodentia. Comp.
Other members of the Order Rodentia, such as ground squirrel (Spermophilus parryii), marmot (Marmota), or beaver (Castoridae), may be indicated.
The specimens of two new species of chigger mites were collected from two species of rodents (order Rodentia) the Yunnan red-backed vole (also called the Yunnan Chinese vole or the large oriental vole) Eothenomys miletus (Thomas 1914) (Andrew and Xie 2009) in the family Cricetidae and the sladeni rat Rattus sladeni (Linnaeus 1758) in the family Muridae.
The Asian musk shrew (Suncus murinus), also called the Asian house shrew, is a small mole-like mammal belonging to the family Soricidae (order Soricomorpha), and wild rats are classified in the family Muridae (order Rodentia).