"In the other forms the number (vertebrae) varies between twenty and thirty three, the latter being spider monkeys. The proportion in the spider monkeys of the genus Ateles, almost three to one; in the other longest—tailed genera it is rarely so large as two to one." —Encyclopaedia Britannica, 1910

Side View of Skeleton of South American Spider Monkey

"In the other forms the number (vertebrae) varies between twenty and thirty three, the latter being…

An illustration of an adult male orangutan viewed from the side. The orbit part of the skull is more rounded than humans. The cranium, top part of the skull, and the mouth area are elongated compared to humans.

Adult Male Orangutan Skull Viewed from Side

An illustration of an adult male orangutan viewed from the side. The orbit part of the skull is more…