FUNCTIONAL ADAPTATIONS IN THE PRIMATE SHOULDER GIRDLE
Article first published online: 20 AUG 2009
1964 The Zoological Society of London
Proceedings of the Zoological Society of London
Volume 142, Issue 1, pages 49–66, January 1964
How to Cite
ASHTON, E. H. and OXNARD, C. E. (1964), FUNCTIONAL ADAPTATIONS IN THE PRIMATE SHOULDER GIRDLE. Proceedings of the Zoological Society of London, 142: 49–66. doi: 10.1111/j.1469-7998.1964.tb05153.x
- Issue published online: 29 OCT 2009
- Article first published online: 20 AUG 2009
- [Accepted 9th October, 1962]
Certain quantitative features of the primate shoulder girdle vary in phase with established muscular differences; in the Anthropoidea, between quadrupeds, semi-brachiators and brachiators, and in the Prosiinii between quadrupeds and hangers. These contrasts, together with others not directly associated with muscular features, contribute to the efficiency of tho shoulder mochanism for the typo of locomotion practised by each group. Thus, in brachiators, where the arm is habitually raised–a process comprising rotation of the scapula by m. trapozius and m. serratus magnus, together with abduction of the humerus by in. deltoideus, the insertion of m. trapezius is disposed more laterally and is orientated more cranially than in quadrupods where the arm is seldom, fully raised. The insertion of m. serratus magnus extends more caudally in brachiators and it is orientated so that the muscle fibres are both more nearly parallel to and further away from those of m. trapozius. Again, in brachiators, m. doltoidous inserts moro distally into tho humerus than in quadrupeds. Tho habitually raised position of the arm in brachiators can also be functionally related to a more cranial orientation of the glenoid cavity and to a more lateral projection of the shoulder joint. In semibrachiators, where the arm is sometimes used as in quadrupeds and at others as in brachiators, each of these features is developed to an intermediate degree.
In man, some of these characters are like those of quadrupeds, and others as in brachiators, the pattern conforming to the contrast that while the human arm can, as in brachiators, be freely raised, most movoment occurs when it is, as in quadrupeds, in tho lowered position.
In the Prosimii, contrasts in those bony features between quadrupeds and hangers parallel to some extent those between quadrupeds and brachiators in the Anthropoidea. This can be related to the fact that in hangers, as in brachiators, the body weight is habitually suspended from the raised fore limb.