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a family of fish of the suborder of the ancient sharks (Hexanchoidei). They are carnivorous viviparous fish. They have six to seven pairs of gill openings, a dorsal fin, and ridge-like serrated teeth on the lower jaw. Hexanchidae are found in tropical and subtropical waters of the Atlantic, Indian, and Pacific oceans at depths of 200–1,800 m and are also numerous in the Mediterranean Sea.
Hexanchidae feed chiefly on fish. Several genera are known, including Hexanchus griseus, with body length up to 8 m and six pairs of gill openings; Heptanchus perlo, with body length up to 2.1 m and seven pairs; and Notorynchus platycephalus, which reaches 2 m in length. Hexanchidae are not found in the seas of the USSR. They have been known since the Jurassic period.
A. A. SVETOVIDOVA