The postcranial morphology of the arboreal white-cheeked mangabey (Lophocebus albigena) differs from that of partly terrestrial Cercocebus mangabeys (C. torquatus, C. galeritus). Its humerus has a reduced greater tuberosity, weak muscular insertions on the humeral shaft, less salient trochlear keels, a thinner diaphysis and less retroflexed medial epicondyle. The femur of L. alhigena is characterized by a lowered greater trochanter, a thinner shaft, a flattened distal epiphysis and a wide and shallow patellar surface. The forelimb is short relative to other limb segments. L. alhigena has attained these skeletal features by deducting the ancestral terrestrial adaptations, such as skeletal robusticity and joint restriction. Influences of phylogenetic inertia on the development of skeletal morphology are discussed.