text:  Experts disagree over whether <unk> were ancestral to modern amphibians ( frogs , <unk> , and <unk> ) , 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 <unk> called <unk> , or even as descendants of both groups ( with <unk> evolving from <unk> and frogs and <unk> evolving from <unk> ) . Recent studies place a family of <unk> called the <unk> as the closest relatives of modern amphibians . <unk> in teeth , skulls , and hearing structures link the two groups . 
  