Any of various fishes of the class Sarcopterygii, having fins that are rounded and fleshy, suggesting limbs. One group of lobe-finned fish are thought to be ancestors of amphibians and other land-dwelling vertebrate animals. They first appeared in the Ordovician Period and are extinct except for the coelacanth and lungfish. Also called sarcopterygian. Compare ray-finned fish. See also crossopterygian.