Much of the skull is occupied by the two large orbits. These originally South American primates now range northward into Mexico. The tail is retained in arboreal groups for balance and steering while airborne, but is lost in some terrestrial species. Their molar teeth on lower jaw have five prominent cusps. Apes are specialists for knuckle-walking and brachiating, with forelimbs longer than hindlimbs, and a shorter trunk in comparison to monkeys.
Apes are intelligent mammals with large brains.
The siamang, featured in the pictures and media clips here, is the largest gibbon species and a famous vocal inhabitant of many zoos.