Any member of the vertebrate class Osteichthyes, including the great majority of living fishes and all the world's sport and commercial fishes. Also called Pisces, the class excludes jawless fishes (hagfishes and lampreys) and cartilaginous fishes (sharks, skates, and rays). There are more than 20,000 species worldwide, all with a skeleton at least partly composed of true bone. Other features include, in most species, a swim bladder (an air-filled sac to give buoyancy), gill covers over the gill chamber, bony platelike scales, a skull with sutures, and external fertilization of eggs. Bony fishes occur in all freshwater and ocean environments.
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