Ontogenetic shape trajectories in Procrustes form space.

(A-B) Principal components analysis of Procrustes shape variables from the eruption of deciduous dentition (age group 2) to adulthood (age group 6). (A) Endocranial form space; principal component 1 vs. principal component 2. (B) Splanchnocranial form space: principal component 1 vs. principal component 2. Convex hulls represent pooled sexes of age groups 2–6 for each species; age group labels denote age group means, while lines are B-spline curves of the average species-specific trajectories. Colours: green = chimpanzee; dark grey = gorilla; orange = orangutan.