Functional morphology of the anthropoid talocrural joint

Abstract

The form and function of the talocrural joint of anthropoids is frequently used to infer positional behaviors of fossil catarrhines without clear and quantitative data to support these inferences. Specifically, greater medial and posterior trochlear wedging, shallower trochleae and more obliquely oriented groove for the tendon of the flexor hallucis longus muscle on the talus, and a more anteriorly oriented posterior talar facet on the calcaneus, have been hypothesized to reflect a greater emphasis on vertical climbing in anthropoids. This research evaluated these features in extant anthropoids, and compared them between pairs of taxa representing different emphases on climbing in their locomotor repertoires. Although taxa vary in these features, they do not do so in predicted ways. Results suggest that these aspects of talocrural joint functional morphology are not associated with climbing in extant anthropoids, and cannot be used in isolation to predict behavior of fossil taxa. Although this research has evaluated only broad, pairwise contrasts between diverse groups of extant taxa, variation identified here provides justification for a more in depth, detailed analysis of talocrural functional morphology in anthropoids.