. Bulletin of the British Museum (Natural History), Geology. io6 CLASSIFICATION OF BABOONS The Olorgesailie form shows the same characters of humerus, ulna and femur as the Kanjera. In addition, there is evidence of extreme terrestrial adaptation in the foot bones. Among living Cercopithecinae it was found that the more ground-living the species, the shorter and stouter its proximal and middle phalanges of digits II-V, in both the hand and the foot. In Fig. 15 the robusticity of manual and pedal proximal phal- anges is expressed by plotting their breadth against their length. In spite of the f
. Bulletin of the British Museum (Natural History), Geology. io6 CLASSIFICATION OF BABOONS The Olorgesailie form shows the same characters of humerus, ulna and femur as the Kanjera. In addition, there is evidence of extreme terrestrial adaptation in the foot bones. Among living Cercopithecinae it was found that the more ground-living the species, the shorter and stouter its proximal and middle phalanges of digits II-V, in both the hand and the foot. In Fig. 15 the robusticity of manual and pedal proximal phal- anges is expressed by plotting their breadth against their length. In spite of the fact that phalanges of all digits except hallux and poUex are included, there is a clear progression in relative shortness almost without overlap, from the arboreal genera Cercopithecus and Cercocebus through Macaca, Mandrillus and Papio to the extremely terrestrial gelada. The phalanges of Pleistocene Theroptthecus are even more stubby than those of its living relative. A second complex of features in the foot which is. Fig. 27. Olecranon angulation and triceps action. Diagrammatic sagittal section through elbow. A. Centre of rotation of elbow joint. B. Midpoint of insertion of triceps tendon. T. Line of action of M. triceps. Triceps is at maximum mechanical advantage when angle ABT = 90°. ACj represents the corresponding position of the forearm in a terrestrial form with olecranon angle of about 60°; AC^ the equivalent in an arboreal form with olecranon angle of about 10°.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Museum (Natural History). London : BM(NH)
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