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Castoridae
 
 
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The family Castoridae contains the two living species of beaver
Beaver

Beavers are two primarily nocturnal, semi-aquatic species of rodent, one native to North America and one to Eurasia. They are known for building dams, canals, and lodges ....
 and their fossil
Fossil

Fossils are the preserved remains or trace fossil of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous Rock formations and sedimentary rock layers is known as the fossil record....
 relatives. This was once a highly diverse group of rodent
Rodent

Rodentia is an Order of mammals also known as rodents, characterised by two continuously growing Incisors#The_Rodent_incisor in the upper and lower jaws which must be kept short by gnawing....
s, but is now restricted to a single genus, Castor.
orids are medium sized mammals, although large compared with most other rodents.






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The family Castoridae contains the two living species of beaver
Beaver

Beavers are two primarily nocturnal, semi-aquatic species of rodent, one native to North America and one to Eurasia. They are known for building dams, canals, and lodges ....
 and their fossil
Fossil

Fossils are the preserved remains or trace fossil of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous Rock formations and sedimentary rock layers is known as the fossil record....
 relatives. This was once a highly diverse group of rodent
Rodent

Rodentia is an Order of mammals also known as rodents, characterised by two continuously growing Incisors#The_Rodent_incisor in the upper and lower jaws which must be kept short by gnawing....
s, but is now restricted to a single genus, Castor.

Characteristics

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
Dam

A dam is a barrier that Reservoirs surface water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates, levees, and Dike are used to manage or prevent water flow into specific land regions....
 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 incisor
Incisor

Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below....
s and the typical rodent dental formula
Dentition

Dentition is the tooth development of teeth and their arrangement in the mouth.All mammals except the monotremes, the xenarthrans, the pangolins, and the cetaceans have up to four distinct types of teeth, with a maximum number for each....
:

Evolution

The earliest castorids belong to the genus Agnotocastor
Agnotocastor

Agnotocastor is an extinct member of the mammalian family Castoridae. Unlike its modern relative, this species took the place of muskrats in the rivers of North America during the Oligocene epoch....
,known from the late Eocene
Eocene

The Eocene Geologic time scale is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era....
 and Oligocene
Oligocene

The Oligocene is a geologic epoch of the Paleogene Geologic Timescale and extends from about 33.9 million to 23 million years before the present....
 of North America
North America

North America is the northern continent of the Americas, situated in the Earth's northern hemisphere and almost totally in the western hemisphere....
 and Asia
Asia

Asia is the world's largest and most populous continent. It covers 8.6% of the Earth's total surface area and, with over 4 billion people, it contains more than 60% of the world's current human population....
 (Rybczynski, 2007). Other early castorids included genera such as Steneofiber
Steneofiber

Steneofiber is an extinct genus of beaver from Eurasia.This small, 30 cm long creature probably lived in large fresh water lakes, like present day beavers....
, from the Oligocene and Miocene
Miocene

The Miocene is a Geologic time scale of the Neogene period and extends from about 23.03 to 5.33 million years before the present. As with other older geologic periods, the rock beds that define the start and end are well identified but the exact dates of the start and end of the period are uncertain....
 of Europe, the earliest member of the subfamily Castorinae, which contains castorids closely related to living beavers (Korth, 2002). Their teeth were not well suited to gnawing wood, suggesting that this habit evolved at a later point, but they do appear adapted to semi-aquatic living. Later, such early species evolved into forms such as Palaeocastor
Palaeocastor

Palaeocastor is an extinct genus of beaver that lived in the North American Badlands during the late Oligocene period....
 from the Miocene
Miocene

The Miocene is a Geologic time scale of the Neogene period and extends from about 23.03 to 5.33 million years before the present. As with other older geologic periods, the rock beds that define the start and end are well identified but the exact dates of the start and end of the period are uncertain....
 of Nebraska
Nebraska

Nebraska is a U.S. state located on the Great Plains of the Midwestern United States and Western United States.Nebraska probably gets its name from the archaic Chiwere language words ?? Br?sge or the Omaha-Ponca language N? Bth?ska meaning "flat water," after the Platte River that flows through the state....
. Palaeocastor was about the size of a muskrat, and dug corkscrew
Corkscrew

A corkscrew is a tool for drawing Cork from wine bottles. Generally, it consists of a pointed metallic helix attached to a handle. The user grips the handle and screws the metal point through the cork , entwining the cork and corkscrew so that moving one moves the other....
-shaped burrows up to deep.

Giant forms evolved in the Pleistocene
Pleistocene

The Pleistocene is the epoch from 1.8 million to 10,000 years Before Present covering the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
, including Trogontherium in Europe, and Castoroides
Castoroides

Castoroides is an extinct genus of giant beavers that lived in North America during the Pliocene. There are two known species:*Castoroides leiseyorum ...
 in North America. The latter animal was as large as a black bear
Black bear

Black bear may refer to:*American Black Bear*Asiatic Black Bear, including its subspecies *Maine Black Bears, the athletic teams representing the University of Maine...
, yet had a brain only marginally larger than that of modern beavers. Its shape suggests that it would have been a good swimmer, and it probably lived in swamp
Swamp

A swamp is a wetland featuring temporary or permanent inundation of large areas of land, by shallow bodies of water. A swamp generally has a substantial number of hammock , or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation....
y habitats (Savage and Long, 1986).

Taxonomy

McKenna and Bell (1997) divided Castoridae into two subfamilies, Castoroidinae and Castorinae. More recent studies (Korth, 2002; Rybczynski, 2007) have recognized two additional subfamilies of basal castorids, Agnotocastorinae and Palaeocastorinae, which is followed here. Within the family, Castorinae and Castoroidinae are sister taxa (Korth, 2002; Rybczynski, 2007); 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 (Rybczynski, 2007). Palaeocastorinae includes beavers that are interpreted as fossorial
Fossorial

A fossorial organism is one that is adapted to digging and life underground such as the badger, the naked mole rat, and the mole salamanders Ambystomatidae....
 (burrowing) (Rybczynski, 2007), as are nothodipoidins and Migmacastor
Migmacastor

Migmacastor is an extinct member of the beaver family, Castoridae, known from a single species, Migmacastor procumbodens. Only a single specimen has been reported, a skull from the late Oligocene or early Miocene of Nebraska ....
 (Korth, 2007b). The following taxonomy is based on Korth (2002, 2007a,b) and Rybczynski (2007), with preference given to the latter where the these differ.

  • Family Castoridae
    • †Migmacastor
      Migmacastor

      Migmacastor is an extinct member of the beaver family, Castoridae, known from a single species, Migmacastor procumbodens. Only a single specimen has been reported, a skull from the late Oligocene or early Miocene of Nebraska ....
    • Subfamily †Agnotocastorinae (paraphyletic)
      • Tribe †Agnotocastorini
        • †Agnotocastor
          Agnotocastor

          Agnotocastor is an extinct member of the mammalian family Castoridae. Unlike its modern relative, this species took the place of muskrats in the rivers of North America during the Oligocene epoch....
        • †Neatocastor
      • Tribe †Anchitheriomyini
        • †Anchitheriomys
          Anchitheriomys

          Anchitheriomys is an extinct member of the beaver family, Castoridae. Until recently, it was placed in a closely related family of rodents, Eutypomyidae , but have since described a partial skull that shows similarities to another early beaver, Agnotocastor....
        • †Propalaeocastor
          Propalaeocastor

          'Propalaeocastor' is a poorly-known extinct genus of beaver from the early Oligocene of Europe and Asia. Recently described material of a new species of Propalaeocastor, P....
        • †Oligotheriomys
    • Subfamily †Palaeocastorinae
      • †Palaeocastor
        Palaeocastor

        Palaeocastor is an extinct genus of beaver that lived in the North American Badlands during the late Oligocene period....
      • †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

          Castoroides is an extinct genus of giant beavers that lived in North America during the Pliocene. There are two known species:*Castoroides leiseyorum ...
        • †Procastoroides
      • Tribe †Trogontheriini
        • †Trogontherium
        • †Boreofiber
        • †Euronexomys
        • †Youngofiber
        • †Asiacastor
    • Subfamily Castorinae
      • †Palaeomys or †Chalicomys
      • †Steneofiber
        Steneofiber

        Steneofiber is an extinct genus of beaver from Eurasia.This small, 30 cm long creature probably lived in large fresh water lakes, like present day beavers....
      • †Zamolxifiber
      • †Romanofiber
      • †Schreuderia
      • †Sinocastor
      • †Hystricops
      • Castor - modern beavers


See also

  • Beaver
    Beaver

    Beavers are two primarily nocturnal, semi-aquatic species of rodent, one native to North America and one to Eurasia. They are known for building dams, canals, and lodges ....