Bony Orbital Form in Two Groups of Catarrhini Primates: How Asymmetrical Are They?

The aim of this study was to compare left and right osseous orbit forms in two different Catarrhini primate genera using geometric morphometric techniques. The analysis was carried out on 20 well-preserved skulls from gorilla (Gorilla gorilla, n=10) and papios (drill [Mandrillus leucophaeus, n=3] and mandrill [M. sphinx, n=7]) from animals kept in zoo, which were photographed in their frontal norm. A set of 4 sagittal landmarks on the face and 23 semilandmarks on each orbita contour were used. According to results, right and left orbitas were similar in size but not in shape, appearing to be significative for individual-by-side interaction (fluctuating asymmetry). It is supposed this due to a developmental instability due to captivity life. Fluctuating asymmetry was clearly higher among gorillas, seeming logical that hominoidea primates suffering in captivity is higher than among cercopithecids (papios and mandrills). Side directional differences were significative only for papios. We supposed it to be due to a stronger stroke of lateralized mastication as, compared to gorillas, mandibles in papios are longer.