Are talonids more evolvable than trigonids? Evidence from North American Paleogene primates

John P. Hunter, Naava Schottenstein, & Jukka Jernvall. Ann. Zool. Fennici 61: 539–552.

Upper molar crown types, characterized by the number, location, and shape of the main cusps alongside the presence and the orientation of cutting edges, facilitate rapid classification of basic morphotypes. This enables broad taxonomic and temporal sampling efficiently. Our research extends the application of crown types to lower molars and premolars of Paleogene primates in North America to categorize the variety of lower premolars and molars that arose among early primates and that likely played a key role in their diversification. We further took advantage of the natural division of lower cheek teeth into a higher (i.e., earlier developing) trigonid and a lower (i.e., later developing) talonid to test evolutionary hypotheses arising from differences in developmental timing. We tested whether the talonid evolved greater diversity in shape than the trigonid, and we assessed the relative contributions of the trigonid and the talonid to the temporal pattern of dental diversification in early primates. In our data, crown type richness generally varied with species sampling...