The Silverback Lowland Gorilla Skeleton is cast from a very large male specimen. The largest primate, Gorillas spend most of their day eating to support their large mass. Males can be up to twice the weight of females. The characteristic head shape of male Gorillas is the result of structures designed to process the voluminous amount of low nutrient vegetation that comprise their diet. The prominent sagittal crest on the top of the skull supports temporal jaw muscles that provide grinding strength to large molars, and meets a bony shelf, the nuchal crest, at the back of the head. Female Gorillas have a smaller sagittal crest. Compared to Chimpanzees and Bonobos, Gorillas have longer arms relative to leg size, and shorter, broader hands and feet. Original skeleton is courtesy of the Philadelphia Zoo.