; order Rodentia, suborder Sciuromorpha)
A family of semi-aquatic rodents that have dense fur, valvular nostrils and ears, enlarged, webbed hind feet, strongly clawed pentadactyl limbs, horizontal, scaly, paddle-like tails, and small eyes and ears. Both sexes possess paired anal scent glands (see anal glands). The skull is massive, the cheek teeth rooted and hypsodont. There are two species in a single genus, Castor, which has a Holarctic distribution.
Subjects: Zoology and Animal Sciences.