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Skull of a beaver

The family CASTORIDAE contains the two living species of beavers and their fossil relatives. This was once a highly diverse group of rodents , but is now restricted to a single genus, Castor .

CONTENTS

* 1 Characteristics * 2 Evolution * 3 Taxonomy * 4 References

CHARACTERISTICS

Main article: Beaver
Beaver

Castorids are medium-sized mammals, although large compared with most other rodents. They are semiaquatic , with sleek bodies and webbed hind feet, and are more agile in the water than on land. Their tails are flattened and scaly, adaptations that help them manoeuvre in the water. Castorids live in small family groups that each occupy a specific territory, based around a lodge and dam constructed from sticks and mud. They are herbivores, feeding on leaves and grasses in the summer, and woody plants such as willow in the winter. They have powerful incisors and the typical rodent dental formula :

DENTITION

1.0.1-2.3

1.0.1.3

EVOLUTION

Euhapsis barbouri fossil

The earliest castorids belong to the genus Agnotocastor , known from the late Eocene
Eocene
and Oligocene
Oligocene
of North America
North America
and Asia
Asia
. Other early castorids included genera such as Steneofiber
Steneofiber
, from the Oligocene
Oligocene
and Miocene
Miocene
of Europe, the earliest member of the subfamily Castorinae, which contains castorids closely related to living beavers. Their teeth were not well suited to gnawing wood, suggesting this habit evolved at a later point, but they do appear adapted to semiaquatic living. Later, such early species evolved into forms such as Palaeocastor from the Miocene
Miocene
of Nebraska
Nebraska
. Palaeocastor was about the size of a muskrat, and dug corkscrew -shaped burrows up to 2.5 m (8.2 ft) deep. Eucastor tortus Mounted skeleton of Castoroides ohioensis

Giant forms evolved in the Pleistocene
Pleistocene
, including Trogontherium
Trogontherium
in Europe, and Castoroides
Castoroides
in North America. The latter animal was as large as a black bear , yet had a brain only marginally larger than that of modern beavers. Its shape suggests it would have been a good swimmer, and it probably lived in swampy habitats.

TAXONOMY

McKenna and Bell divided Castoridae into two subfamilies, Castoroidinae and Castorinae. More recent studies have recognized two additional subfamilies of basal castorids, Agnotocastorinae and Palaeocastorinae, which is followed here. Within the family, Castorinae and Castoroidinae are sister taxa; they share a more recent common ancestor with each other than with members of the other two subfamilies. Both subfamilies include semiaquatic species capable of constructing dams. The Palaeocastorinae include beavers that are interpreted as fossorial (burrowing), as are nothodipoidins and Migmacastor . The following taxonomy is based on Korth and Rybczynski, with preference given to the latter where these differ.

* FAMILY CASTORIDAE

* † Migmacastor

* Subfamily †Agnotocastorinae (paraphyletic )

* Tribe †Agnotocastorini

* † Agnotocastor * †Neatocastor

* Tribe †Anchitheriomyini

* † Anchitheriomys
Anchitheriomys
* † Propalaeocastor * †Oligotheriomys

* Subfamily †Palaeocastorinae

* † Palaeocastor * †Capacikala * †Pseudopalaeocastor

* Tribe †Euhapsini

* †Euhapsis * †Fossorcastor

* Subfamily † Castoroidinae

* †Priusaulax (placement in Castoroidinae questionable)

* Tribe †Nothodipoidini

* † Eucastor * †Microdipoides * †Nothodipoides

* Tribe †Castoroidini (paraphyletic)

* † Monosaulax * †Prodipoides * † Dipoides * † Castoroides
Castoroides
* † Procastoroides

* Tribe †Trogontheriini

* † Trogontherium
Trogontherium
* †Boreofiber * †Euroxenomys * †Youngofiber * †Asiacastor

* Subfamily Castorinae

* †Chalicomys (also incorrectly "Palaeomys") * † Steneofiber
Steneofiber
* †Zamolxifiber * †Romanofiber * †Schreuderia * †Sinocastor * †Hystricops

* Castor - modern beavers

* North American beaver
North American beaver
, Castor canadensis * Eurasian beaver , Castor fiber * † Castor californicus
Castor californicus

REFERENCES

* ^ Lancia, R.A.; Hodgdon, H.E. (1984). Macdonald, D., ed. The Encyclopedia of Mammals. New York: Facts on File. pp. 606–609. ISBN 0-87196-871-1 . * ^ A B C D E Rybczynski N., 2007. Castorid phylogenetics: implications for the evolution of swimming and tree-exploitation in beavers Journal of Mammalian Evolution 14(1):1-35. * ^ A B C Korth W.W., 2002. Comments on the systematics and classification of the beavers (Rodentia, Castoridae) Journal of Mammalian Evolution 8(4):279-296. * ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 284. ISBN 1-84028-152-9 . * ^ Savage, R.J.G., and Long, M.R. 1986. Mammal
Mammal
Evolution: an Illustrated Guide. Facts on File, New York, pp. 120–121 ISBN 0-8160-1194-X . * ^ McKenna, Malcolm C., and Bell, Susan K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp. ISBN 0-231-11013-8 . * ^ A B Korth W.W., 2007b. The skull of Nothodipoides (Castoridae, Rodentia) and the occurrence of fossorial adaptations in beavers Journal of Paleontology 81(6):1533-1537. * ^ Korth W.W., 2007a. A new genus of beaver (Rodentia, Castoridae) from the Miocene
Miocene
(Clarendonian) of North America
North America
and systematics of the Castoroidinae based on comparative cranial anatomy Annals of Carnegie Museum 76(2):117-134.

Wikispecies
Wikispecies
has information related to: CASTORIDAE

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* v * t * e

Extant families in order Rodentia

* Kingdom: Animalia * Phylum: Chordata * Class: Mammalia * Infraclass: Eutheria
Eutheria
* Superorder: Euarchontoglires
Euarchontoglires

Sciuromorpha
Sciuromorpha
("Squirrel-like")

* Aplodontiidae (Mountain beaver) * Gliridae (Dormice) * Sciuridae (Squirrels, chipmunks, marmots, susliks and prairie dogs)

Castorimorpha
Castorimorpha
("Beaver-like") Castoroidea
Castoroidea
Castoridae (Beavers) Geomyoidea
Geomyoidea
Geomyidae (Pocket gophers) Heteromyidae
Heteromyidae
(Kangaroo rats and mice, pocket mice)

Myomorpha
Myomorpha
("Mouse-like") Dipodoidea Dipodidae
Dipodidae
(Jerboas, jumping mice and birch mice) Muroidea
Muroidea
Platacanthomyidae
Platacanthomyidae
(Oriental dormice) Spalacidae (Zokors, bamboo rats, mole rats, blind mole rats) Calomyscidae (Mouse-like hamsters) Nesomyidae
Nesomyidae
(Malagasy rats and relatives) Cricetidae
Cricetidae
(Hamsters and relatives) Muridae (House mouse and relatives)

Anomaluromorpha ("Anomalure-like")

* Anomaluridae (Anomalures) * Pedetidae (Springhares)

Hystricomorpha ("Porcupine-like")

* Ctenodactylidae (Gundis) * Diatomyidae (Laotian rock rat) * Hystricidae (Old World porcupines)

Phiomorpha
Phiomorpha
Bathyergidae (Blesmols) Petromuridae (Dassie rat) Thryonomyidae (Cane rats) Caviomorpha (New World hystricognaths) Erethizontidae (New World porcupines) Caviidae (Cavies) Cuniculidae (Pacas) Dasyproctidae
Dasyproctidae
(Agoutis and acouchis) Dinomyidae (Pacarana) Capromyidae (Hutias) Ctenomyidae (Tuco-tucos) Echimyidae
Echimyidae
(Spiny rats and coypus) Octodontidae (Degus and relatives) Abrocomidae (Chinchilla rats) Chinchillidae (Chinchillas and visca