Polypteriformes

Article By:

Boschung, Herbert T. Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama.

Bailey, Reeve M. Division of Fishes, Museum of Zoology, University of Michigan, Ann Arbor, Michigan.

Last reviewed:January 2021

DOI:https://doi.org/10.1036/1097-8542.536700

A distinctive and apparently ancient order of actinopterygian fishes comprising the subclass Cladistia, commonly known as bichirs and reedfishes. The following combination of characteristics distinguishes members of the order Polypteriformes 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, with each supported by a spine; lobed pectoral fin with its rays supported by ossified radials; a 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 pairs of gill arches (rather than five pairs, as is typical for actinopterygians). See also: Actinopterygii; Scale (zoology); Swim bladder

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