Sub-order ANTHROPOIDEA

Family Pongidae. Great apes and gibbons

The great apes and gibbons are of special interest because they most resemble man in their basic morphology; they have the same dental formula and their teeth are similar in form. One of the main differences is that, in man, the upper incisors overlap the lower incisors labially in occlusion and the inter-incisor relationship only becomes edge-to-edge late in life when the teeth are very worn; in apes, the upper incisors slightly overlap the lowers immediately after eruption but thereafter the relationship is edge-to-edge.

The canines are much larger in apes and, unlike human canines, show marked sex dimorphism. The lower canine is accommodated in occlusion in a diastema between I2 and the upper canine, and a smaller diastema between the lower canine and the mesial slope of P3, accommodating the upper canine, is frequently present. Both diastemas are smaller in the female in accord with the smaller canines.

In apes, the incisors form a flat curve, as in man. However, the upper premolars and molars (cheek teeth) are arranged in straight lines which usually converge slightly distally so that the widest part of the upper arch is between the canines and the narrowest between the M3 (Fig. 10.1). The lower tooth arch is naturally somewhat similar though, as in man, because the upper cheek teeth overlap the lower ones, the lower arch is narrower than the upper.

In man, the sides of the upper arch are slightly rounded with the widest part not between the canines but between M1, and the narrowest between the M2 and the M3, forming what is defined as a parabolic curve.