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Functional Anatomy and Adaptation of Male Gorillas ( Gorilla gorilla gorilla ) With Comparison to Male Orangutans ( Pongo pygmaeus )
Author(s) -
Zihlman Adrienne L.,
Mcfarland Robin K.,
Underwood Carol E.
Publication year - 2011
Publication title -
the anatomical record: advances in integrative anatomy and evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.678
H-Index - 62
eISSN - 1932-8494
pISSN - 1932-8486
DOI - 10.1002/ar.21449
Subject(s) - pongo pygmaeus , gorilla , quadrupedalism , postcrania , biology , climbing , anatomy , bipedalism , forelimb , prehensile tail , scapula , primate , hominidae , trunk , arboreal locomotion , evolutionary biology , zoology , ecology , biological evolution , paleontology , habitat , taxon , genetics
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.