Measurements of postnatal growth of the skull of Pan troglodytes verus using lateral cephalograms

The postnatal growth of the viscerocranium in relation to the neurocranium of Pan troglodytes verus has been investigated using standardized lateral cephalograms. Sex and age were determined on the basis of cranial morphology and the skulls were divided into four age groups: infantile, juvenile, subadult and adult. The cephalograms were traced on transparencies and specific anatomical landmarks were identified for the measurement of lines angles and the area of the neurocranium and viscerocranium. The results showed that the skull of Pan troglodytes verus exhibits klinorhynchy. During postnatal growth it develops towards airorhynchy, but never shows true airorhynchy. In the infantile age group the measured area of the neurocranium is larger than that of the viscerocranium. The measured area of the viscerocranium increases until adulthood and is larger than that of the neurocranium in the subadult and adult group. From the results we conclude that in Pan troglodytes verus growth of the neurocranium seizes early in juvenile individuals, whereas the viscerocranium grows until adulthood. This may reflect an adaptation to the masticatory system.