The family is made up of only two living species of beaver.
Beavers are the largest rodents in North America and Eurasia, the only places they are found.
They are heavy aquatic rodents perhaps best know for making dam homes responsible for causing, at times, large lakes and ponds. The order Rodentia consists of small to medium sized mammals which share the common characteristic of a single pair of upper and lower incisors that are specialized for gnawing. Rodentia is the largest order of living mammals, containing approximately 1500 species. The skulls of rodents vary in length from .25 inch to over 10 inches long. The tooth count does not exceed 22 except in the Mole Rat which has 28 teeth.