by N. V. Parin
Body elongate and compressed or fusiform (in Lepidocybium and larger Ruvettus). Two nostrils on each side of snout. Lower edge of preopercle entire. Mouth large; upper jaw not protractile; lower jaw more or less projecting beyond tip of the upper. Teeth strong, fang-like in anterior part of upper jaw. Gillrakers usually undeveloped. 2 dorsal fins, the first longer than second, anal fin similar to second dorsal in shape and size, often preceded by 1 or 2 free spines; detached finlets usually present behind dorsal and anal fins (except in 4 genera of which only Diplospinus occurs in area); pectoral fins small or moderate; pelvic fin small, with 1 spine and 0-5 rays; caudal fin moderate, forked. Scales absent or small. Cycloid, sometimes modified. Lateral line single or double. No keels on caudal peduncle (except in Lepidocybium).
Oceanic epi- and mesopelagic or benthopelagic in about 150 to 1200 m. Fast-moving predators (except Diplospinus), some of them migrating upwards at night. Not common inside the area. Carnivorous, feeding on fishes, squids and crustaceans. Spawning throughout the year in warm waters but probably seasonal in area; eggs and larvae pelagic. No special fisheries in area; the flesh is edible but oily in some species.
Genera 14, most of them considered monotypic; in Clofnam area 7.
Recent revisions (none of entire family): Matsubara Iwai (1958—anatomy and relationships of 8 genera), Parin & Becker (1972—species review of 10 genera).