''Migmacastor'' is an extinct member of the beaver family,

Castoridae The family Castoridae contains the two living species of beavers and their fossil relatives. A highly diverse group of rodents within this family once roamed the earth, but only a single genus is extant today, '' Castor''. Characteristics Ca ...

, known from a single species, ''Migmacastor procumbodens''. Only a single specimen has been reported, a

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

from the late Oligocene or early

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

Nebraska Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the sout ...

. Features of the

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, t ...

of ''Migmacastor'' indicate they were used to dig. Other extinct beavers, including the better-known ''

Palaeocastor ''Palaeocastor'' ('prehistoric beaver') is an extinct genus of beavers that lived in the North American Badlands during the late Oligocene period to early Miocene. ''Palaeocastor'' was much smaller than modern beavers. There are several specie ...

'', were also fossorial (digging), but ''Migmacastor'' may have become a burrower independently.Korth, William W.; Rybczynski, Natalia (2003), "A new, unusual castorid (Rodentia) from the earliest Miocene of Nebraska", Journal of Vertebrate Paleontology 23 (3): 667–675, doi:10.1671/2371

References

Prehistoric beavers Oligocene rodents Miocene rodents Cenozoic mammals of North America Prehistoric monotypic mammal genera Prehistoric rodent genera {{paleo-rodent-stub