Fig. 6.

Centroid size of Pan troglodytes molars with no C6 (red), with a suspected C6 (blue) and with a C6 present (green). Molars without a C6 are on average smaller than those with a suspected C6 or a C6 present, but the lower size ranges overlap. The dentine crowns of the smallest molars of each group (arrows) as well as the biggest molar are plotted to scale to show that equally small molars exhibit dentine horn spacing and C6 expression that is consistent with predictions of the patterning cascade model. The Procrustes shape coordinates of the three smallest teeth from each group are superimposed in the lower right corner to highlight the dentine ridge shape differences [for clarity a white surface model is plotted only for the smallest tooth without C6 (red ridge curve); for the other two groups only the ridge curve is plotted].