Department of Anthropology, University of Oregon
Thursday Morning, 301D
Can geometric morphometrics identify the relationship of post cranial form and function? The current study examines the appositional articular morphology (AAM) of the talo-crural joint exploring this question.
408 matched tibiae and tali from 245 adult (M3) and 163 subadult (M1-M2) from 12 catarrhine taxa, 6 hominoid and 6 cercopithecoid (H. sapiens, G. gorilla, P. troglodytes, P. paniscus, Pongo spp., Hylobatidae, M. fascicularis, M. mulatta, M. thibetana, P. hamadryas, C. guereza, N. larvatus) were studied. Landmarks were placed on the articular surfaces and edited using Landmark Editor software. Generalized Procrustes analysis, principal component analysis, multivariate regression and singular warps analysis were used to examine differences in joint shape.
Important features differentiate terrestrial and arboreal taxa that provide flexibility and stability on horizontally placed irregular surfaces of different textures in the former, and medially placed curvilinear surfaces with irregular surface movement in the latter. Trochlear facet and trochlear shape and plane, medial malleolar and medial talar facet shape and orientation, and trochlear crest and facet groove shape and displacement, differentiate the arboreal and terrestrial forms in adults (M3). In arboreal taxa these features provide increased range of dorsiflexion and inversion and increased flexibility, and in terrestrial taxa they increase stability in dorsiflexion and allow increased angular excursion.
A behavioral effect was observed. Adult articular shape sorted by substrate preference across superfamily. When the AAM subsets were examined, arboreal subadults and adult clustered, while terrestrial taxa separated, changing in shape from subadult to adult across superfamily, possibly reflecting change in substrate use.
Funding provided in part by NSF BCS0452539, and the University of Oregon, and funding to the CPRC by NIH Grant No. P40 RR003640.