The head is large, and the nose is pointed. The moderate-sized ears are rounded and covered with short hair. The whiskers are long. The hind foot has four well-developed toes, each with a sharp, curved claw and a row of stiff bristles extending beyond the claw. The grinding surfaces of the cheek teeth are shaped like a figure eight, or sometimes like a kidney.
Females have three or four pairs of mammae.
Octodonts inhabit coastal areas, foothills, and the Andes Mountains to elevations of 3,500 meters or more. They live both in cultivated areas and on barren, rocky slopes. They are good diggers, especially Aconaemys and Spalacopus. They either construct their own burrows or dwell in crevices, rock piles, fences, hedgerows, or the holes of other animals. These agile rodents carry their tail erect while running and sometimes climb shrubs or trees.