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any of the approximately 115 species of small, quick-moving marine fishes in the family Chaetodontidae (order Perciformes). Butterfly fishes are found among tropical reefs around the world but are concentrated in the Indo-Pacific oceanic region. Butterfly fishes are deep-bodied and thin from side to side, with a single dorsal fin and a small mouth with tiny, bristlelike teeth. The jaws are sometimes drawn out into a relatively long snout, as in the longnose butterfly fish (Chelmon rostratus) of the Indo-Pacific and the longsnout butterfly fish (Prognathodes aculeatus) of the Atlantic. Most species have strong, prominent spines on the front portions of their dorsal fins.