Amphibians are said to have evolved from the fish called a lungfish.

ans.

amphibians are first land vertebrates that were evolve around 370 million years ago. the first amphibian is known to evolved from a lungfish, sarcopterygian, in devonian period. this fish had characteristics that the amphibians to adapt in dry lands, such as presence of bony-limbed fins and lungs.

the adult amphibians use respiration in land, while bony fins of lung fish were evolved into limbs of amphibians.

thus, the correct word to be filled in the black is 'sarcopterygian.'