Scapular correlates of muscle morphology in <i>Macaca mulatta</i>

Abstract

Compressive forces in the upper extremity are produced by muscle contraction and weight bearing. These forces are primary in shaping the scapula and are reflected in discernible structural correlates. Statistical analysis of both selected scapular dimensions and weights of the surrounding muscles can be utilized to infer differences in locomotor behavior. Muscles of the upper extremity and shoulder region of 13 adult rhesus macaques (<i>Macaca mulatta</i>) were dissected and dried. The weights of these muscles were compared through the use of bivariate statistical analyses to several dimensions of the bony scapula. A significant correlation existed between the weights of the individual intrinsic compressive muscles, the summed weight of the intrinsic compressive muscle mass and length dimensions of the scapula. With the exception of m. supraspinatus, nonsignificant correlations were obtained between the intrinsic compressive muscles and the selected breadth dimensions. Higher Pearson’s r values existed for all but one of the intrinsic compressive muscles and those dimensions of the scapula which contained a length component. The results were compared with those of another study of the scapula and musculature of Papio cynocephalus. The results of these two studies demonstrated opposing conclusions. Another study on the scapula and musculature of <i>Macaca fascicularis</i> (n = 6) showed concordance with the results obtained in this study. The advisability of lumping macaques and baboons into a single gross locomotor category is questioned.