 Experts disagree over whether <unk> were ancestral to modern amphibians ( frogs , salamanders , and caecilians ) , or whether the whole group died out without leaving any descendants . Different hypotheses have placed modern amphibians as the descendants of <unk> , another group of early tetrapods called <unk> , or even as descendants of both groups ( with caecilians evolving from <unk> and frogs and salamanders evolving from <unk> ) . Recent studies place a family of <unk> called the <unk> as the closest relatives of modern amphibians . Similarities in teeth , skulls , and hearing structures link the two groups . 
