any of about four species of marine fishes constituting the family Fistulariidae (order Gasterosteiformes), found in tropical waters. Cornetfishes are long and slim, with a long, tubular snout and a distinctive filament (the end of the backbone) extending back, beyond the forked tail fin. The fishes are rather flattened from top to bottom and are either scaleless or have hard plates embedded in their skins. The largest cornetfishes grow to about 1.8 metres (6 feet) in length. Species include the cornetfish (Fistularia tabacaria), a large, blue-spotted, green or gray inhabitant of the Atlantic, and the red, or rough, flutemouth (F. villosa), a large, pink or reddish fish, also of the Atlantic.
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