NEW CHARACTERS FOR THE FUNCTIONAL INTERPRETATION OF PRIMATE SCAPULAE AND PROXIMAL HUMERI

The study of muscle function in nonhuman primates through the techniqu e of electromyography (EMG) has facilitated the identification of spec ific functional roles for muscles in particular behaviors. This has le d to a more complete understanding of the biomechanics of certain regi ons of the musculoskeletal system, and should facilitate our ability t o identify morphological features useful in the functional interpretat ion of fossil material. The current paper represents one such investig ation of a new set of morphometric characters of the scapula and proxi mal humerus suggested by EMG analyses of shoulder muscle function. A s et of new metric variables were examined on the scapulae and proximal humeri of 25 species of extant anthropoid primates, as well as on cast s of scapulae and humeri of three fossil primate taxa. The variables a re primarily related to the line of action and attachments of the rota tor cuff muscles. The position of the scapular spine, the degree of la teral expansion of the subscapular fossa, the size and shape of the su bscapularis insertion facet on the lesser tubercle, and the orientatio n of the infraspinatus insertion facet on the greater tubercle all app ear to successfully sort the extant taxa into locomotor groups. Their appearance on the fossil specimens generally supports previous functio nal interpretations of each taxon's locomotor abilities based on a var iety of other characters, suggesting that these traits are equally app licable to fossil material. (C) 1995 Wiley-Liss, Inc.