Variation and Integration of the Simple Mandibular Postcanine Dentition in Two Species of Phocid Seal

Abstract

Pinnipeds generally swallow prey whole, and most have simple, homodont, nonoccluding cheek teeth. We investigated whether cheek teeth in seals are more variable and weakly integrated than in terrestrial Carnivora. We measured mandibular length and crown length of mandibular postcanines (PCs) in ringed seals (Pusa hispida; n ¼ 912) from the Canadian Arctic, and harp seals (Pagophilus groenlandicus; n ¼ 636) from Newfoundland and Labrador. PC size was uncorrelated or only weakly correlated with adult mandibular length. PC length and mandibular length were strongly bilaterally symmetrical (r � 0.8 between left and right sides). PC size was moderately variable (coefficients of variation [CVs] ; 7‐10%), and CV varied with position in the toothrow. Adjacent PCs were correlated more strongly in size (to r . 0.8) than PCs more distant from one another. In summary, PC size in ringed and harp seals was slightly more variable than cheek teeth in complex dentitions of fissipeds, and the 2 seals were similar to fissipeds in strong bilateral symmetry in mandibular and PC size, patterned variation along the toothrow, and correlated size between adjacent PCs.