The Evolution of Dental Eruption Sequence in Artiodactyls

Abstract

The sequence of eruption of the second generation of teeth varies across taxa, is highly functional, and is strongly influenced by genetic effects. We assessed postcanine dental eruption sequence across artiodactyls in order to test two hypotheses: 1) dental eruption sequence is a good phylogenetic character for artiodactyls; and, 2) eruption sequence is adaptive and associated with life history variables like postnatal growth and longevity in artiodactyls (Schultz’s Rule). We examined postcanine eruption sequence in 81 genera (100 species) spanning ten families of Artiodactyla. Our ancestral state reconstruction supports the interpretation that the third molar erupted last in the ancestor of Artiodactyla, and that the fourth premolar erupted after the third molar in the ancestor of Ruminantia. Our results indicate that eruption of the third molar last evolved secondarily in the caprines, likely sometime in the Miocene. Overall, our results support the hypothesis that dental eruption sequence is phylogenetically conserved in artiodactyls. Caprines occupy high elevation habitats, and we hypothesize that evolution of their unique dental eruption sequence may be associated with limited resource availability in high elevation mountain systems and the necessity to process a wide range of vegetation types.