lobefin, common name for any of a group of lunged, fleshy-finned, bony fishes, also called crossopterygians, that were dominant in the Devonian period and may have given rise to amphibians. They had heavy, ungainly bodies and stumpy paired fins, which may have been the precursors of the limbs of four-footed animals. Known from their fossils, the lobefins were thought to be extinct until 1938, when a live coelacanth was caught in deep water off S Africa. Since then other specimens have been discovered in the Madagascar area. The coelacanths are a marine branch of the lobefins. The coelacanth discovered in 1938, Latimeria chalumne, is a brown to steel-blue fish 5 ft (150 cm) long, with circular, overlapping scales, a laterally flattened three-lobed tail, a spiny dorsal fin, and a vestigial lung. The fish give birth to live young. In 1998 a closely related coelacanth, L. menadoensis, was discovered in Indonesia. See also lungfish. Lobefins are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Crossopterygii.
See S. Weinberg, A Fish Caught in Time (2000).