A North American Beaver.
Rodentia is an order from the Mammalia class. They are characterised by a single pair of continuously growing incisors in each of the upper and lower jaws which must be kept short by gnawing.
All rodents share the characteristic of dentition highly specialised for gnawing. This specialisation gives rodents their name from the Latin, rodere, to gnaw and, dentis, of tooth. All rodents have a single pair of upper and a single pair of lower incisors, followed by a gap, and then one or more molars or premolars. Rodent incisors grow continuously and must be kept worn down by gnawing.