any of about 70 species of marine and freshwater fishes of the family Exocoetidae (order Atheriniformes), sometimes placed in the family Hemirhamphidae. Halfbeaks are named for their unusual jaws-the upper is short and triangular, and the lower is long, slim, and beaklike. The fish are silvery, slender, and up to about 45 centimetres (18 inches) long. They can skip across the water to escape from danger, and some are able to make short, gliding flights like the related flying fish (q.v.). Many halfbeaks are egg layers; the others bear live young
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