Extant Euarchontoglires


Order: Rodentia
Family: 30
Species: 1'702

The Rodentia represents over 40% of all placental mammal species, and over 38% of all placental mammal species. There are 3 Suborders within the Rodentia which are defined by jaw musculature:

Suborder: Sciuromorpha (Squirrel-like rodents)
Families: 7
Species: 377

Suborder: Myomorpha (Mouse-like rodents)
Families: 5
Species: 1'137

Suborder: Caviomorpha (Cavy-like rodents)
Families: 18
Species: 188

Skeleton of a brown rat (Rattus norvegicus)
Bristol City Museum, UK



The Sciuromorpha include rodents such as squirrels, beavers, chipmunks, prairie dogs and woodchucks. They inhabit a variety of environments from streams and forests to mountains and deserts. They live in a variety of homes that varies between species. Most squirrels for example live in a dry nest and twig nest in trees called a drey. Prairie dogs and chipmunks dig burrows and beavers build lodges out of mud and sticks in a pool or lake. Unlike other sciuromorphs, beavers have webbed feet that enable them to swim with extreme proficiency. The Sciuromorpha also include the flying squirrel which morphologically looks very similar to the flying lemur in that it has large folds of skin that stretch out between the limbs to allow gliding between branches.


Example species:

Eastern chipmunk
Tamias striatus

Length: 15.5-16.5 cm
Weight: 80-125 g
Social unit: Individual
Region: South-East Canada to Central and South-East USA
Status: Common

Eastern chipmunk (Tamias striatus)
Roaming wild at West Yellowstone Grizzly Bear and Wolf Sanctuary, USA


Black tailed prairie dog
Cynomys ludovicianus

Length: 28-30 cm
Weight: 0.7-1.5 kg
Social unit: Group
Region: South-West Canada to North Mexico
Status: Lower risk

Black tailed prairie dog (Cynomys ludovicianus)
Twycross Zoo, UK


Eastern grey squirrel
Sciurus carolinensis

Length: 23-28 cm
Weight: 300-700 kg
Social unit: Variable
Region: South and South-East Canada to South USA and Europe
Status: Common

Eastern grey squirrel (Sciurus carolinensis)
Roaming wild at Bristol Zoo and Gardens, UK



The Myomorpha include the popular pets; rats, mice, gerbils and hamsters, plus voles, lemmings jerboa. The Myomorpha comprises over a quarter of all mammal species. They have elongated snouts giving them a pointed face, long whiskers and comparatively large ears. They are mostly nocturnal and are found world wide in almost all habitats. The only continent on which they are not found is Antarctica. Their diet consists of seeds, berried and nuts, habitat dependant. Most species live in nests, but the naked mole-rat for example lives in an underground burrow and voles occupy aquatic habitats. Species such as the jerboa have developed extremely long legs and very large ears in order to detect and escape from predators. This is because they tend to inhabit environments that comprise wide open spaces and are thus vulnerable to predation.

Water vole (Arvicola terrestris)
Bristol City Museum, UK


Example species:

Malagasy giant rat
Hypogeomys antimena

Length: 30-35 cm
Weight: 1-1.5 kg
Social unit: Group
Region: West Madagascar
Status: Endangered



The Caviomorpha are the most diverse order of Rodentia. They include the largest of all rodents; the capybara. Capybaras are semi-aquatic and as such have partially webbed feet. Their sensory organs are placed high on their head so that they can still see, hear and breathe whilst swimming. Caviomorpha also inhabit mountainous, forested, desert and stream habitats with arboreal, aquatic, and ground dwelling species such as the naked mole rat. Species also included in the Order are porcupines, chinchillas, guinea pigs and coypu for example. The Order generally encompasses all rodents that do not fit into the other two Orders, but the members are generally related by a relatively large head, a sturdy body, a short tail and slender legs.


Example species:

Hydrochaerus hydrochaeris

Length: 1.1-1.3 m
Weight: 35-66 kg
Social unit: Variable
Region: North and East South America
Status: Common

Capybara (Hydrochaerus hydrochaeris)
Phoenix Zoo, Arizona, USA


Dolichotis patagonum

Length: 43-78 cm
Weight: 2 kg
Social unit: Pair
Region: South South America
Status: Lower risk

Female Mara and two young (Dolichotis patagonum)
Whipsnade Wildlife Park, UK


Author: Emma-Louise Nicholls
Last updated: 20th November 2005
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Websites produced by students on the MSc Palaeobiology programme in the Department of Earth Sciences at the University of Bristol for academic year 2005-6