The maxillary sinus in the higher primates.

The presence or absence of a functional maxillary sinus cavity has been established in 55 specimens of higher primates. These specimens have been further examined to define differences between the two groups and factors which might be responsible. Skull and facial dimensions have been compared with those of the maxillary sinus and demonstrate an increase in sinus size with size of skull and orbit, and an inverse relationship with occipito-nasion/occipito-alveolar ratio. Whilst skull dimensions are on average larger in those with a functional sinus, a number of small monkeys have a well-developed sinus. In those monkeys without a functional sinus cavity, the potential space is encroached upon by orbit and teeth and occupied by spongiform bone. In addition, it is not possible to distinguish the monkeys which possess a functional sinus as a separate group on the grounds of diet, habitat, dentition, classification and geographical distribution.