bichir

(redirected from Polypterid)
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Related to Polypterid: Polypteriformes, bichirs

bichir

(bĭch`ər), common name for African freshwater fishes as of the family Polypteridae, and particularly for those of the genus Polypterus. Bichirs are among the most primitive of the ray-finned fishes, or Actinopterygii, the dominant group of modern fishes. The long, narrow body of Polypterus is 2 to 3 ft (60–90 cm) in length and covered by thick, rhombic scales made of an enamellike substance called ganoine. Such scales were also present in the earliest ray-finned fishes, now extinct, and are quite different from those of other living fishes. The dorsal fin of the bichir is split into a row of small, saillike finlets that are erected when the animal is agitated. Like the sharks and the rays, it has a pair of spiracles. The bichir seems especially adapted to life in dry environments. Instead of the swim bladderswim bladder,
large, thin-walled sac in some fishes that may function in several ways, e.g., as a buoyant float, a sound producer and receptor, and a respiratory organ. The swim bladder, or air bladder, is located in the dorsal portion of the body cavity and is filled with gases.
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 of most ray-finned fishes, it has a pair of lungs, somewhat like those of the lungfisheslungfish,
common name for any of a group of fish belonging to the families Ceratodontidae, Lepidosirenidae, and Protopteridae, found in the rivers of Australia, South America, and Africa, respectively.
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, which enables it to survive out of water for several hours. It also resembles the lungfishes in having a pair of external gills when newly hatched. The bichir is a bottom-dwelling fish, found in the Nile and in the rivers of W Africa. When these rivers overflow in late summer, it moves out to spawn in the flood marshes. It is sometimes caught as a food fish. In addition to the various species of Polypterus, the bichir family includes the reedfish, Erpetoichthys calabaricus, similar in character and distribution, but with a longer, more eellike form. Bichirs are classified in the phylum ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
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, subphylum Vertebrata, class Actinopterygii, order Polypteriformes, family Polypteridae.