The role of modularity in the evolution of primate postcanine dental formula: integrating jaw space with patterns of dentition.

The assembly of a phenotype into modules or developmental fields, which are semiautonomous units in development and function, seems to be one of the strategies to increase the capacity to produce phenotypic variation. In mammals the upper dentition is formed on two distinct developmental units, wherein incisors are formed on the primary palate, which is derived from the embryonic frontonasal process, and the other teeth (canine, premolar, and molar) are formed on the alveolar bone, which is derived from the maxillary process (termed herein as PALATE2). The aim of the present work was to analyze the variations in size and number of premolar and molar teeth in primate dentition and to correlate these morphometrical parameters with the relative size of these tooth classes with respect to PALATE2.