Amphibians are some- times viewed as transitional between fish and reptiles, or as stand-ins for basal tetrapods, but these are not correct views. Instead, the major families of amphibians diversified very early in their evolutionary history, and modern representatives, especially anurans, have many de- rived characters (Duellman and Trueb, 1994; San Mauro et al., 2005). Amphibians are well known for their complex life cycles, where aquatic larvae metamorphose into terrestrial or semi-aquatic adults. However in some species, individuals are aquatic or terrestrial their entire lives while in other species, adults transition between terrestrial and aquatic life styles for breeding every year. Thus, chemical signaling can be com- pared and contrasted in aquatic versus terrestrial environments from a developmental perspective (within a species) and from an evolutionary perspective (across species). Another advantageous feature is that many amphibian chemosignals are peptides or proteins so there is a rel- atively direct link between the chemosignal and the genome. In this way, the evolution of chemosignal sequence, structure, and function can be studied.