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The mountain beaver (''Aplodontia rufa'') is a North American rodent. It has several common names, including: aplodontia, boomer, ground bear, and giant mole. The name sewellel beaver comes from ''sewellel'' or ''suwellel'', the Chinookan term for a cloak made from its pelts. This species is the only living member of its genus, ''Aplodontia'', and family, Aplodontiidae. It should not be confused with true North American and Eurasian beavers, to which it is not closely related.〔“Beavers” in ''The New Encyclopedia of Mammals''. David Macdonald (ed). Oxford university Press, 2001. Pages 590-591.〕〔“Wood Beaver” in ''The New Encyclopedia of Mammals''. David Macdonald (ed). Oxford university Press, 2001. Pages 596-597.〕 == Characteristics == Mountain beavers are brown, but their fur can range from slightly more reddish to more blackish depending on subspecies, with a light patch under each ear. The animals have distinctively short tails. Adults weigh about , with a few specimens topping . Total length is about , with a tail length of . The skull is protrogomorphous; it has no specialized attachments for the masseter muscles as seen in other rodents. It is flattened and lacks a postorbital process. The baculum is thin and distinctly forked. The penis is about in length. The male does not have a true scrotum, but the testes move into a position called semiscrotal during the breeding season. Mountain beavers have an unusual projection on each molar and premolar tooth, which is unique among mammals and allows for easy identification of teeth. This projection points toward the cheek on the upper tooth row, but points toward the tongue on the lower. The cheek teeth lack the complex folds of other rodents and instead consist of single basins. They are hypsodont and ever-growing. Two upper and one lower premolars are present, along with all the molars, giving a dental formula of Mountain beavers cannot produce concentrated urine. They are thought to be physiologically restricted to the temperate rain forest regions of the North American Pacific coast and moist microenvironments inland due to their inability to obtain sufficient water in more arid environments. Their karyotype is 2''n'' = 46. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mountain beaver」の詳細全文を読む スポンサード リンク
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