Polypteriformes

(vertebrate zoology) An ancient order of actinopterygian fishes distinguished by thick, rhombic, ganoid scales with an enamellike covering, a slitlike spiracle behind the eye, a symmetrical caudal fin, and a dorsal series of free, spinelike finlets.

A distinctive and apparently ancient order of actinopterygian fishes, also called the Cladistia or the bichirs. Their characters include thick, rhombic, ganoid scales with an enamellike covering; a slitlike spiracle behind the eye; a well-ossified internal skeleton; a symmetrical caudal fin, basically heterocercal, with the upper part continuous with the dorsal fin (see illustration); a dorsal series of free, spinelike finlets, each supported by a radial bone; a distinctive pectoral fin base with three enlarged radial bones; and paired ventral lungs.

Bichir (Polypterus endlicheri), length to 3 ft (90 cm). (After G. A. Boulenger, Catalogue of the Fresh Water Fishes of Africa in the British Museum, vol. 1, 1909)

This order consists of a single family, the Polypteridae, that is known from the Eocene. The two Recent genera, Polypterus, with about 10 species, and Erpetoichthys, with 1 species, are confined to fresh waters of tropical Africa. See also Actinopterygii; Chondrostei.