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

Exploring the influence of suspension on ulna articular surface shape in anthropoid primates


Paleoanthropology, Senckenberg Center for Human Evolution and Paleoecology and Department of Early Prehistory and Quaternary Ecology, Eberhard Karls University of Tübingen

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We examined the correspondence between ulna articular surface shape variation and suspensory locomotion. Researchers have identified skeletal adaptations to suspension in primates that perform high proportions of forelimb-dominated locomotion (e.g., brachiation). There are multiple influences, however, on the appearance of the limb skeleton, including the demands of limb activity, phylogenetic constraints, and size. Thus, it is important to take these potential influences into account when examining the relationship between skeletal morphology and suspensory behavior. In addition, geometric morphometric techniques allow us to explore variation of ulna articular surface shape in a wide range of extant anthropoids and potentially find new aspects of skeletal shape that correspond with suspension.

We collected 18 three-dimensional landmark coordinates on ulnae of 12 extant species using a Microscribe digitizer. We explored shape variation using principal components analysis and studied covariation between shape and potential influences on skeletal morphology (i.e., brachiation, phylogeny, and centroid size) using multivariate regression. The first and second principal components of variation, which represented different aspects of trochlear and radial notch shape and accounted for approximately 70% of the overall variation, grouped brachiating hominoids and platyrrhines. Furthermore, quadrupedal cercopithecoids and platyrrhines grouped together along these same two principal components. As confirmed by regression analysis, these aspects of ulna articular shape variation clearly correspond with differences in use of suspensory and pronograde quadrupedal behavior. However, overall articular surface shape variation did have a significant relationship with phylogeny and centroid size as well, illustrating the importance of incorporating these factors into functional analyses.

This study was funded by the Volkswagen Foundation, National Science Foundation, grant number BCS-0849204, L.S.B. Leakey Foundation, Wenner-Gren Foundation.

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