The thumb is short and only slightly opposable. A fold of skin along the arm that extends to the side of the chest represents a vestigial parachutelike membrane. The legs are about one-third longer than the arms, and the foot is larger than the hand but also elongated and narrow, differing in the relatively greater development of the first toe. The other four toes are united at the base by a web of skin, and they function as a single unit in opposition to the first toe, providing good grasping ability for the feet. The palms and soles are padded.
Females have a single pair of mammae in the chest region, and the males have a penis bone.
The salivary glands are greatly enlarged, as in the langurs and colobus monkeys. The stomach is large, and the intestine is relatively long, due partly to the elongated caecum. The members of this family have fewer teeth than other primates. The upper incisors are often large, and the upper canines are elongate and sharp. The lower front teeth project forward and slightly upward, as in the Lemuridae.