Rodentia

Rodents (from Latin , 'gnawing') are a group of mammals characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species belong to the order Rodentia ( or ). They are native to all major landmasses except Antarctica and several oceanic islands, though they have subsequently been introduced to most of these landmasses by human activity.

Rodents are extremely diverse in their ecology and lifestyles and can be found in almost every terrestrial habitat, including human-made environments. Species can be arboreal, fossorial (burrowing), saltatorial/ricochetal (leaping on their hind legs), or semiaquatic. However, all rodents share several morphological features, including having only a single upper and lower pair of ever-growing incisors. Well-known rodents include mice, rats, squirrels, prairie dogs, porcupines, beavers, guinea pigs, and hamsters. Rodentia and Lagomorpha (rabbits, hares, and pikas) are sister groups, sharing a single common ancestor and forming the clade of Glires. Lagomorphs also have incisors that grow continuously, but are distinguished by an extra pair of incisors on the upper jaw.