African fish, genus Polypterus, found in tropical swamps and rivers. Cylindrical in shape, some species grow to 70 cm/2.3 ft or more. They show many 'primitive' features, such as breathing air by using the swimbladder, having a spiral valve in the intestine, having heavy bony scales, and having larvae with external gills. These, and the fleshy fins, lead some scientists to think they are related to lungfish and coelacanths.