Functional anatomy of forelimb muscles in Guianan Atelines (Platyrrhini: Primates)

Abstract

In French Guiana, spider and howling monkeys exhibit significant differences in their locomotor and postural habits. This paper presents some qualitative and quantitative data on the forelimb muscles of howling and spider monkeys associated with the movements of the forelimb involved in these positional modes. In red howlers, m. supraspinatus functions as the main humeral abductor during clambering and climbing. In contrast, m. deltoideus is the main humeral abductor involved in climbing and arm-swinging activities in spider monkeys. Both atelines possess well-developed mm. latissimus dorsi, pectorales, and dorsoepitrochlearis, all associated with forelimb movements involved in frequent climbing and clambering. Howlers are similar to capuchins in distal forelimb muscle morphology that favors pronograde quadrupedal activities. On the other hand, spider monkeys possess well-developed elbow flexors and supinator which favor arm-suspensory behavior. Moreover, the similarity of the extrinsic digital flexor musculature between spiders and hylobatids underlines the important role of these muscles during arm-swinging and clambering.