The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Functional morphology of proximal caudal vertebrae in nonprehensile-tailed primates


Department of Anthropology, The University of Texas at Austin

Thursday 9:30-9:45, Ballroom B Add to calendar

Functional morphologists have devoted considerable attention to the structure and function of prehensile tails. By contrast, little attention has been paid to nonprehensile tails despite the fact that this tail type characterizes the majority of mammalian taxa. Here, we compare proximal caudal vertebral anatomy among nonprehensile-tailed primates in the context of a comparative mammalian sample. We evaluate linear and angular measurements with known biomechanical significance against tail length in order to investigate the anatomical changes associated with tail loss/reduction. Preliminary results demonstrate that at the levels of the first and mid-proximal vertebrae, an increase in tail length is associated with craniocaudally longer vertebral bodies with more circularly-shaped proximal articular surfaces, longer spinous processes, and transverse processes that are more laterally expanded and point more caudally and ventrally. Prezygapophyseal orientation does not appear to change with respect to tail length at these vertebral levels. At the level of the transition vertebra, results (for features present) are similar to those of first and mid-proximal vertebrae, but the relationship to tail length appears weaker. Generally, comparisons of proximal caudal vertebrae among nonprimate mammals that vary in tail length confirm the trends observed for primates. These features likely afford longer-tailed mammals enhanced proximal tail flexibility, as well as greater surface area for attachment and improved leverage of tail musculature, compared to shorter-tailed mammals. Our findings provide an anatomical basis for future studies of nonprehensile tail kinematics and may contribute to our understanding of the anatomy associated with tail loss in primate evolution.

This research is funded by NSF (DDIG BCS-1156016 to G.A.R.) and The Leakey Foundation (to G.A.R.).

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