Date of Graduation


Document Type


Degree Name

Master of Arts in Anthropology (MA)

Degree Level





J. Plavcan

Committee Member

Claire Terhune

Second Committee Member

Lucas Delezene


Anatomy, Primatology


The few available comparative studies of prehensile tail anatomy in primates have established that several features of the caudal vertebrae are associated with adaptation to the increased loading of the tail during prehension. Given that the caudal vertebrae are anchored to the sacrum, it stands to reason that sacral morphology should also covary with tail prehensility. Convergent evolution of prehension in ateline and cebine primates and clear variation in the use of tails among taxa raises questions not only of how sacral morphology differs between prehensile and non-prehensile taxa, but whether different prehensile-tailed taxa evolved the same solutions to the biomechanical demands of prehension. The first step in addressing these problems is to document and measure the anatomical correlates of prehension in the sacrum.

A comparative study of primate sacra was completed among the following genera: Alouatta, Ateles, Cacajao, Cebus, Chiropotes, Lagothrix, Macaca, Pithecia, and Saimiri (total n = 103). The genera were split into fully-, semi-, and non-prehensile groups; Alouatta, Ateles, and Lagothrix were categorized as fully-prehensile, Cebus as semi-prehensile, and the remainder as non-prehensile. Linear measurements for 16 anatomical variables were analyzed. Univariate and multivariate analyses returned some degree of significant results. While some measurements were more meaningful than others, morphological differences in relative size and transverse expansion of spinous processes, relative size of features associated with postulated muscle attachment, and relative size of articular surfaces of sacral vertebrae exist among individuals of varying prehensility. Thus, basic anatomical correlates of prehension were identified, and questions of morphological adaptation to prehension can be asked.