Body short, egg-like. Mantle muscular, not fused with head. Anterior mantle margin in larvae and early juveniles straight, in later juveniles and adults strongly protruding forward on ventral side, reaching level of anterior eye margin and almost covering funnel from below. Fins in larvae and juveniles tongue-like, wide (fin width in newborns exceeding mantle width), located in the middle of mantle; in adults kidney-shaped and shifted to posterior half of mantle such that anterior fin margin is near midline of ventral mantle side, and posterior margin reaches or exceeds end of body.
Arms in larvae and juveniles very short, in adults moderately long, arm suckers in 2 rows. 1st-3rd arm pairs connected at bases with deep membrane. Arm structure differing greatly in adult males and females. In males right 1st and 2nd arms connected from inside by muscular band up to half their lengths; suckers extend up to arm tips; on 3rd arms there are 5 strongly enlarged suckers, including 2 (in central part of arm) very large ones, at right angle to one another. In females arms not connected with membrane, without enlarged suckers, ends of 1st and 2nd arms without suckers. Longest arms in males are 3-4th, in females 2-3rd. Tentacles retractable, very long, whip-like, with unwidened short club bearing 8 rows of microscopically small suckers. Gladius absent.
Large oval bilobed photophore on ventral side of ink sac, noticeable even in newborns. Luminous mucus with luminescent bacteria may be ejected through funnel by muscular contraction so that animal may "shoot with fire". Color very bright, vivid, with white fin bases and metallic iridescence on head and body. Egg size in ovary 1.5-2.0 by 1.3-1.8 mm, before hatching 2.5 mm. ML in adult females up to 25 mm. Adult female originally described as Heteroteuthis atlantis G. Voss, 1955.
Lives predominantly over the slopes, spawning on the bottom at bathyal depths. Juveniles and subadults perform ample diurnal migrations. Populations of the Western and Eastern Atlantic are probably isolated.