Meeting Abstract

12.3  Friday, Jan. 4  Patterns of development and diversity in the crocodilian skull JASZLICS, A.*; PARDO, J.D.; University of Texas at Arlington, University of Nebraska at Lincoln; University of Calgary jaszlics@huskers.unl.edu

Variation in ontogenetic trajectories plays a critical role in shaping morphological diversity of the vertebrate skull. Crown group crocodilians are a potentially informative research group for this phenomenon because they demonstrate extensive morphological diversity in the skull despite conservative ecologies. Previous studies of crocodilian skull morphology suggest that variation correlates to biomechanical constraint during feeding. In order to test whether the diversity of crocodilian skull morphologies reflects variation in developmental trajectories, we constructed ontogenetic trajectories in all four major extant crocodilian lineages (Alligatoridae, Crocodylidae, Tomistoma and Gavialis), using geometric morphometric analysis of growth series within and between lineages. We found that the entire skull is tightly integrated throughout ontogeny for all taxa. Differences in adult skull shapes between crocodilian genera primarily reflect variations in juvenile morphology, as well as variation in the overall length of the ontogenetic trajectory. Although skull development in Gavialis is tightly integrated, the observed pattern of growth differs significantly from that seen in all other crocodilian genera. Because this divergent trajectory is associated with landmarks in the rostrum and suspensorium, we hypothesize that the unique feeding mechanism of true gharials constrains morphology throughout ontogeny, which shapes both the aberrant ontogenetic trajectory and adult morphology of this species. These results suggest that divergent morphologies can evolve despite ontogenetic constraint.