Rodentia

There are about 2,277 species in the order Rodentia (33 families, 481 genera), (Latin Rodere, "to gnaw"), making up 40% of the class Mammalia. They can be found on every continent, except Antarctica. Depending on the species, they can be classified either in semiaquatic, arboreal, or fossorial. Both Rodentia and the order Lagomorpha, which includes hares, rabbits are sister groups and are both under the clade Glires.

Fossil records have found that rodents were first sighted in the late Paleocene and early Eocene (54 million years ago and was known to have high carbon dioxide levels). Now extinct species like Castor californicus (giant beaver), S. florensis (cave rat), N. pinckneyi (prehistoric capybara), P. pattersoni (Very large), J. monesi (biggest known rodent), so forth, were much larger rodents than what we commonly see. Only the capybara (Hydrochoerus hydrochaeris) is the largest living rodent.
Although most rodents are herbivores, some species like mice, rats, Chinchillas, are omnivores. This helps them especially in environments of humans.
Depending on species, the size range of sexes can be different. Female bias sexual dimorphism can be sighted in chipmunks and Male sexual dimorphism can be seen in mole rats, ground squirrels, and other species. It is believed that in male chipmunks that seeing larger females is a sign of good reproductive outcome.

One of the most noticeable Characteristics of the rodent is their constantly growing incisors of both upper and lower jaw (normal number range of teeth on a rodent is 22, and does not contain anterior premolars or canines), and that is how they also got their order name from. Unless they keep gnawing, their incisors could grow either to their throat or into their skull. If you look at their skulls, most rodents have a "gap" in between their incisors and cheek teeth, this is also called a diastema.
The molars on rodents are able to grind food up, they are large and can be ridged or angular.
Their jaws are well structured for chewing, but groups can vary in muscles of the jaw.
Squrriels, chipmunks, and other rodents with a "cheek pouch" is a feature that is used for storing food.

For the most part, rodents have a good sense of smell, hearing, and sight. Those of nocturnal species have eyes and in some cases, susceptible to ultraviolet light. Only rats and mice have limited eyesight.

Their digestive system can absorb about 80% of ingested energy. If they were to eat food containing cellulose, It will be softened and go through the cecum (the bacteria will decrease the food into carbohydrates), after this the rodent will eat its own feces. The nutrients will then be absorbed.

Most squirrels (except for ground squirrels) and chipmunks stay solitary, but mice, rats, prairie dogs are social creatures, living in groups. This can sometimes lead to rat or mouse infestation. It is all due to the high reproduction rate of these species. A common house mouse can start breeding about 5 weeks after being born and the outcome can be up to 50 offspring in a year. The young may be born either altricial(blind, hairless and relatively underdeveloped) or precocial (mostly furred, eyes open and fairly developed) depending on the species.

List:

Suborder Anomaluromorpha
Family Anomaluridae: scaly-tailed squirrels
Family Pedetidae: springhares
Suborder Castorimorpha
Superfamily Castoroidea
Family Castoridae: beavers
Superfamily Geomyoidea
Family Geomyidae: pocket gophers (true gophers)
Family Heteromyidae: kangaroo rats, kangaroo mice
Suborder Hystricomorpha
Infraorder Ctenodactylomorphi
Family Ctenodactylidae: gundis
Infraorder Hystricognathi
Family Bathyergidae: African mole rats
Family Hystricidae: Old World porcupines
Family Petromuridae: dassie rat
Family Thryonomyidae: cane rats
Parvorder Caviomorpha
Family †Heptaxodontidae: giant hutias
Family Abrocomidae: chinchilla rats
Family Capromyidae: hutias
Family Caviidae: cavies, including Guinea pigs and the capybara
Family Chinchillidae: chinchillas, viscachas
Family Ctenomyidae: tuco-tucos
Family Dasyproctidae: agoutis
Family Cuniculidae: pacas
Family Dinomyidae: pacaranas
Family Echimyidae: spiny rats
Family Erethizontidae: New World porcupines
Family Myocastoridae: coypu (nutria)
Family Octodontidae: octodonts
Infraorder Incertae sedis
Family Diatomyidae: Laotian rock rat
Suborder Myomorpha
Superfamily Dipodoidea
Family Dipodidae: jerboas and jumping mice
Superfamily Muroidea
Family Calomyscidae: mouse-like hamsters
Family Cricetidae: hamsters, New World rats and mice, muskrats, voles, lemmings
Family Muridae: true mice and rats, gerbils, spiny mice, crested rat
Family Nesomyidae: climbing mice, rock mice, white-tailed rat, Malagasy rats and mice
Family Platacanthomyidae: spiny dormice
Family Spalacidae: mole rats, bamboo rats, zokors
Suborder Sciuromorpha
Family Aplodontiidae: mountain beaver
Family Gliridae (also Myoxidae, Muscardinidae): dormice
Family Sciuridae: squirrels, including chipmunks, prairie dogs, marmots

Posted on March 30, 2019 02:04 AM by backyardcreature