Functional Anatomy and Adaptation of Male Gorillas (Gorilla gorilla gorilla) With Comparison to Male Orangutans (Pongo pygmaeus)
Article first published online: 1 AUG 2011
Copyright © 2011 Wiley-Liss, Inc.
The Anatomical Record
Volume 294, Issue 11, pages 1842–1855, November 2011
How to Cite
Zihlman, A. L., Mcfarland, R. K. and Underwood, C. E. (2011), Functional Anatomy and Adaptation of Male Gorillas (Gorilla gorilla gorilla) With Comparison to Male Orangutans (Pongo pygmaeus). Anat Rec, 294: 1842–1855. doi: 10.1002/ar.21449
- Issue published online: 14 OCT 2011
- Article first published online: 1 AUG 2011
- Manuscript Accepted: 3 JUN 2011
- Manuscript Revised: 3 MAR 2011
- Manuscript Received: 13 JAN 2011
- body composition;
- locomotor behavior
Great apes diversified during the Miocene in Old World forests. Two lineages, gorillas in Africa and orangutans in Asia, have sexual dimorphisms of super-sized males, though they presumably diverged from a smaller common ancestor. We test the hypothesis that they increased in body mass independently and convergently, and that their many postcranial differences reflect locomotor differences. Whole body dissections of five adult male gorillas and four adult male orangutans allowed quantification of body mass distribution to limb segments, of body composition (muscle, bone, skin, and fat relative to total body mass), and of muscle distribution and proportions. Results demonstrate that gorilla forelimb anatomy accommodates shoulder joint mobility for vertical climbing and reaching while maintaining joint stability during quadrupedal locomotion. The heavily muscled hind limbs are equipped for propulsion and weight-bearing over relatively stable substrates on the forest floor. In contrast, orangutan forelimb length, muscle mass, and joint construction are modified for strength and mobility in climbing, bridging, and traveling over flexible supports through the forest canopy. Muscles of hip, knee, and ankle joints provide rotational and prehensile strength essential for moving on unstable and discontinuous branches. We conclude that anatomical similarities are due to common ancestry and that differences in postcranial anatomy reflect powerful selection for divergent locomotor adaptations. These data further support the evolutionary conclusion that gorillas fall with chimpanzees and humans as part of the African hominoid radiation; orangutans are a specialized outlier. Anat Rec, 2011. © 2011 Wiley-Liss, Inc.