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a family of marine fishes of the order Allotri-ognathi. The ribbonlike body is up to 5.5 m long and 25 cm high. The dorsal fin is long and low except for the high anterior part over the head. The ventral fins are two long, filamentous rays. In motion the body curves like a snake, and the head rises partly over the water; for this reason Regalecidae were thought to be sea snakes. There are two genera, Regalecus and Agrostichthys. Regalecidae inhabit the depths and open parts of the Pacific, Indian, and Atlantic oceans.