text:  One group of <unk> , the <unk> , is also known from <unk> specimens . <unk> like <unk> and <unk> are represented by many fossils preserving skin and external gills . An entire growth series is exhibited in the wide range of sizes among specimens , but the lack of <unk> adapted adult forms suggests that these <unk> were <unk> . Unlike other <unk> , their <unk> skeletons developed quickly but were still partly <unk> when fully mature . Adults likely had an aquatic lifestyle similar to juveniles . Recently , large specimens of <unk> <unk> were described with adaptations toward a terrestrial lifestyle , indicating that not all <unk> were <unk> . 
  