When a tadpole metamorphoses into frog extensive remodelling of the skull occurs. Some of the greatest changes occur in the palatal region, in association with the transformation of the small, terminal mouth opening of the tadpole into the wide gape of the frog. This study will attempt to reconstruct the evolutionary history of this remarkable transformation by describing variability in the metamorphic pattern among frogs, and by comparing them with salamanders and caecilians, which have much less extensive remodelling during metamorphosis. In addition, experimental work on the causal (inductive) relations between palatal structures will serve to further test any proposed evolutionary scenario, by allowing more rigorous determination of which structures are truly comparable between these groups.
