Which order of mammals includes rodents such as rats, squirrels, and beavers? The answer is Rodentia.
Rodentia is the mammalian order that includes rats, squirrels, beavers and thousands of other rodents. It is the largest order of mammals by number of species, representing about 40% of all mammal species. Rodents occupy nearly every major land environment except Antarctica.
Their defining feature is a pair of continuously growing incisors in both the upper and lower jaws. A hard enamel front surface and softer dentine behind it create a self-sharpening edge as the teeth wear down. This adaptation supports gnawing, but rodents have evolved into an enormous range of forms, from tiny mice to capybaras.
Beavers belong to the family Castoridae, squirrels to Sciuridae, and rats and mice occur mainly in the family Muridae. Rodents are sometimes confused with lagomorphs such as rabbits and hares. Both groups have ever-growing incisors, but lagomorphs have an additional small pair of upper incisors behind the main pair.