A distinctive and apparently ancient order of actinopterygian fishes comprising the subclass Cladistia, commonly known as bichirs and reedfishes. The following combination of characters distinguishes the order from all other actinopterygian fishes: elongate body covered with thick, rhombic, ganoid scales; slitlike spiracle behind each eye; well-ossified internal skeleton, including vertebrae with ossified centra and neural canals; maxillae firmly united with the skull; basically heterocercal tail, but with a symmetrical caudal fin, and with the upper part continuous with the dorsal fin; dorsal series of free sail-like finlets, each supported by a spine; lobed pectoral fin with its rays supported by ossified radials; pair of enlarged gular plates; very large intercalar bone; no branchiostegals; bilobed swim bladder (the left lobe less developed than the right) located ventral to and attached to the esophagus, serving as lungs; functional gills; young with a pair of feathery external gills, which are assimilated with age; spiral valve-type intestine; and four rather than five pairs of gill arches as is typical for actinopterygians (see illustration).