SHAPE OF THE PIRIFORM APERTURE IN GORILLA-GORILLA, PAN-TROGLODYTES, AND MODERN HOMO-SAPIENS - CHARACTERIZATION AND POLYMORPHISM ANALYSIS

By using new methodologies based on automatic image analysis, the shap e of the piriform aperture was analyzed in Gorilla gorilla (33 males, 13 females), Pan troglodytes (35 males, 22 females), and modern Home s apiens (30 males, 12 females). The determination of the piriform apert ure index (breadth/height) allowed the authors to demonstrate a marked elongation of the aperture in Home compared with Gorilla and Pan. Ind ividual characterization of the shape was possible with great precisio n and without ambiguity by using Fourier analysis. An absolute, inters pecific partition between Gorilla, Pan, and Home resulted from the can onical discriminant analysis of the Fourier descriptors. However, a cl oseness of shape between some individuals in Pan and some in Gorilla a nd Home was observed, demonstrating a morphological continuum of the s hape of the piriform aperture in hominoids: Pan was in intermediate po sition between Gorilla and Home. Interspecific differences between Hom e and the group Pan-Gorilla were explained principally by the differen ces in elongation (amplitude of the second harmonic) and pentagonality (amplitude of the fifth harmonic) and by differences in orientation o f quadrangularity (phase of the fourth harmonic). Differences in the s hape of the piriform aperture between Pan and Gorilla were explained b y differences in orientation of elongation (phase of the second harmon ic) and by differences in the component of triangularity (amplitude of the third harmonic). In Gorilla and Pan, the little, elongated, and r elatively trapezoidal piriform aperture seems to be a shared primitive feature (plesiomorphic), whereas an elongated piriform aperture seems to be a characteristic and derived feature (apomorphic) of modern Hom e sapiens. (C) 1998 Wiley-Liss, Inc.