 Modern amphibians ( frogs , salamanders , and caecilians ) are classified in Lissamphibia . <unk> appear to have arisen in the Permian . Molecular clock estimates place the first <unk> in the Late Carboniferous , but the first member of Batrachia ( frogs and salamanders , but not caecilians ) is estimated to have appeared in the Middle Permian using the same technique . Using fossil evidence , there are three main theories for the origin of modern amphibians . 
