Tooth size variability and relevance of numerical variation in the Japanese serow

We analysed the variability of the lower cheek teeth of the Japanese serow, Capricornis crispus, from Aichi Prefecture, Japan, based on the coefficient of variation (CV), and examined tooth size variability. The mesiodistal (MD) and buccolingual (BL) crown diameters of permanent cheek teeth were measured, and an index of the crown surface (MD × BL) was calculated. As a result, the CV for MD measurements ranged from 3.6 to 6.3, and that for BL measurements ranged from 3.6 to 6.5. In males and females, the first molar (M1) was the least variable (3.6–4.1) and the second premolar (P2) was the most variable (5.0–6.5), except for the case of BL in females. The crown surface index showed a morphological gradient that increased from mesial to distal, and the values of P2 in both sexes were extremely small. Overall, cheek tooth variability was not influenced by developmental factors, but appeared to be inversely related to functional factors. The highest coefficient of variation was observed for P2, which was characterised by a simple shape with a single cusp, and an extremely small size compared to other teeth. Only P2 showed congenital absence or impaction in the lower dentition. We also confirmed the relationship between tooth size variability and numerical variation.