Orbital asymmetries in tamarins of the genus Saguinus (Primates, Callitrichidae)

The aim of this study was to analyse the orbital asymmetry in Saguinus skulls. The examination was conducted on 13 dry well-preserved skulls, belonging to different species of the genus Saguinus . The sample was studied by means of geometric morphological methods. The photos were taken by a digital camera with high definition. Digital pictures were obtained on the facial plane of each skull, and subsequently 15 semi-landmarks were placed along each orbital ridge. Contralateral orbital asymmetries were compared individually for both size and shape. Interestingly, we discovered statistically significant differences in size, which can be interpreted as orbital area, with the right orbit being larger, as well a significant shape directional asymmetry, which changes affected mostly the lacrimal and temporal edges. Detected orbital asymmetry can be assumed as a normal although unconspicous anatomic adaptative pattern in Saguinus , as it has been described in other primates. The underlying causes remain unknown, although this directional bias may indicate a possible visual lateralization. This is the first demonstration of orbital form asymmetry in this genus.