Mantle narrow, cylindrical or conical, semigelatinous, tapering into very long (longer than mantle itself) acute needle-like tail, sometimes broken off in adults but present in larvae and juveniles. Fin very small, oval or round. Head narrow, with rather long neck and small eyes. Arms 1st-3rd extremely long, thin, flexible, with thread-like ends and very small suckers in 6 rows; 4th arms much shorter, with suckers in 4 rows. Tentacles in juveniles shorter than 1st-3rd arms, with thread-like stalk and long, laterally compressed club with minute suckers in 8-12 rows; protective membranes present only on distal half of club. No fixing apparatus. In adults tentacles fully reduced. Funnel cartilage oval, without tragus and antitragus, mantle cartilage an elongated tubercle. Buccal membrane with 7 lappets, connectives to 4th arms attached ventrally. No photophores. Gladius needle-like, with very long conus. Known ML up to 10.5 cm.
Larvae with spindle-shaped semitransparent mantle, very small petaloid fins and needle-like tail longer than mantle. Neck rather short, without septa. "Snout" (arm-crown pillar) absent. 3rd arms appear at ML approx. 8 mm. Tentacles thick and short, club with 4 (at ML 6-9 mm), then 8 (ML 18 mm) rows of suckers. Thick tentacles and very long acute tail are characteristic.