any deep-sea teleost fish of the genus Trachipterus, esp T. arcticus, related to the ribbonfishes and having a very long tapelike body and a fan-shaped tail fin
any long, ribbon-shaped, silvery fish of the genus Regalecus, of deep tropical waters, having a red dorsal fin along the spine that rises to a crest, and reaching a length of 30 feet (9 meters).