BANBURY, B.L.*; MAGLIA, A.M.; The University of Missouri-Rolla: Comparative cranial development of premetamorphic pelobatid tadpoles (Anura: Pelobatidae)

Adult pelobatid frogs (Anura: Pelobatidae) exhibit extreme variation in the degree of cranial ossification. Scaphiopus and Pelobates have robust hyperossified crania, while Spea is a gracile, poorly ossified frog. Because Scaphiopus and Spea are sister-taxa, this suggests that the condition of hyperossification has either independently evolved twice in the group, or was a plesiomorphic character that was lost in Spea. Herein, we provide baseline quantitative data on the development of the larval chondrocranium and cranial ossification for each genus within Pelobatidae and its closest sister taxa Pelodytidae. We used linear and geometric morphometric methods to analyze size-related ontogenetic shape change prior to metamorphic climax. We discuss areas of regional shape transformation in the chondrocranium among species (as identified by thin-plate spline deformation grids), and comment on the potential implications regarding cranial development and variation in degree of ossification in the group.