We also characterize the keratinized mouthparts of tadpoles as ectodermal appendages and propose that these novel vertebrate structures may have originated by partially co-opting the program that typically mediates development of mineralized teeth. More work is underway to explore this hypothesis!

4) We searched for vestigial dental development on the toothless frog mandible. We found no definitive evidence of tooth rudiments initiating in the lower jaw when teeth are forming on the upper jaw. Unexpected, because evolutionarily lost traits typically form at least partly during development.

3) We evaluated whether the tadpole jaw impacts developing teeth. Keratin may dictate the location of the earliest dental placodes, which are positioned far behind the tadpole "beak". Did keratin similarly displace teeth during the evolution of turtles, birds, & non-avian theropod dinosaurs?

2) We assessed if the genes underlying dental competence are conserved in the late-forming teeth of frogs. We found dental precursor expression patterns consistent with an odontogenic band, comparable to patterns observed in other vertebrates.

In this paper, we 1) describe the precise timing of tooth development in a typical anuran, the Cuban tree frog (Osteopilus septentrionalis). The earliest indication of tooth development is at the final stage of tadpole development (Gosner 40), coinciding with the larval keratinized mouthparts.