paddlefish, large freshwater fish, Polyodon spathula, of the Mississippi valley, also called spoonbill or duckbill and named for its flattened, paddle-shaped snout. The largest specimens weigh well over 150 lb (67.5 kg) and reach 6 ft (183 cm) in length. The snout may be a third of the length of the body; it is equipped with sense organs that assist the fish in finding its prey of small crustaceans, which it strains out with gill rakers (see gill). Paddlefishes are primitive; unlike most modern fishes, they have skins with reduced scales, almost wholly cartilaginous skeletons, and upturned tail fins. They are uniform leaden gray in color. Valued as food fish, their greenish black eggs, like the more highly valued ones of the distantly related sturgeon, are used to make caviar. A Chinese species, Psephurus gladius, found in the Chang (Yangtze) River but now on the verge of extinction is reported to grow some 20 ft (6 m) in length. Paddlefishes are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Acipenseriformes, family Polyodontidae.
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