Body a deep oval (depth usually ~ length), strongly compressed; mouth a horizontal slit when closed, opens at the front, is a beak (without a central suture) composed of teeth fused to the jaws; gill openings small, on side just before pectorals; pectorals short, rounded; no pelvics; dorsal 17-18 rays; anal 14-18 rays; pectoral 12-13 rays; no tail base; dorsal and anal fins long and high, symmetrical, used for locomotion, at rear of body, their rear rays joined to tail fin immediately behind them that is reduced to a vertically elongate, short, blunt rudder, with bony ossicles on its margin, with an undulating rounded profile; skin thick, tough, with small denticles.
Grey brown to dark blue above, often with large pale blotches, silvery below, fins dark.
Size: 332 cm.
Depth near surface, 0-644 m.
Circumglobal, tropical to warm temperate; off Baja and the Gulf of California, and the Galapagos; potentially throughout our region.