This group of rabbits has four teeth in the upper jaw, and two incisors (front teeth) in the bottom jaw. These incisors grow their entire lives. Their appendices are also large and thick, which makes them suited to a life of eating grass. This group is divided into two families: Ochotonidae, which have bodies weighing 0.5kg and resembling mice, and Leporidae, which had long ears and developed rear legs, and runs quickly.