Department of Anthropology, University of Oregon
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Substrate preference has been demonstrated to influence adult talo-crural joint shape among catarrhine taxa independent of superfamily. The current study examines the ontogeny of substrate preference and superfamily effects on talo-crural joint shape.
Proximal talar articular surfaces from 116 catarrhine specimens, representing two closely related hominoids (H. sapiens, P. troglodytes) and two cercopithecoids (M. mulatta, M. fascicularis) formed the study group, with dental eruption subsets (M1, M2, M3) examined for changes during ontogeny. The specimens were laser surface scanned, digitally reconstructed and landmarked. Generalized Procrustes analysis, Procrustes’ distances, regression analysis, and permutation tests were used to evaluate the significance and relative contributions of substrate preference and superfamily on talo-crural joint shape in each ontogenetic subset. The relationship of substrate preference and superfamily within in each subset was assessed using the angle between their respective vectors.
Permutation test results demonstrated shape was highly conserved with all but adult (M3) cercopithecoids S.D. (p=0.022, Bonferroni p< 0.008). Substrate preference became more important in determining joint shape from M1 to M3 (from 12% to 21% of variance), while superfamily became less (31% to 18%). Furthermore, these factors became more independent (62.2°) by M2.
Phylogenetic signal was observed at the M1 stage with progression to an epigenetic signal by M3 i.e., juvenile shape differences are governed more by phylogeny, but by adulthood, use may have a greater influence. Independence of substrate preference from superfamily is consistent with prior observations in larger samples of adult proximal talar and distal tibial facets.
Funding provided in part by NSF BCS-0452539 and the University of Oregon