A gigantic squid. Mantle membranous in larvae, tough and leathery in juveniles and adults, semigelatinous in mature females, spindle-shaped in juveniles and cup-shaped in adults, thick (up to 4-5 cm), smooth. At each mantle-to-funnel fusion site 4-6 conical cartilaginous tubercles; at mantle-to-head fusion site 1 conical tubercle beside anterior end of gladius; all usually poorly visible in adults. Head wide, without "snout" (arm-crown pillar). Eyes on short stalks in larvae, not stalked and globular in juveniles and adults.
Fins in larvae petaloid, very small, in juveniles round, in adults broadly heart-shaped, length in adults up to 60% ML, width somewhat less, anterior fin margin at site of maximum width of lanceola. Arms long, robust, ca. 50% ML, subequal. Suckers in 2 rows, with dentate rings. Some suckers on mid-section of all arms, from 3-5 pairs on 1st to 8-10 pairs on 4th arms converted into strong hooks, covered by skin hood. Transformation begins at ML approx. 45 mm with central tooth becoming elongated, overgrowing others and downturned, two others remaining as small teeth beside the longest. Tentacles not shorter than mantle. Club short, narrow, with 4 rows of suckers in larvae, in adults central rows with 11-12 pairs of large acute hooks with widened base, covered by skin hood, and same number of small marginal suckers. Hooks appearing at ML approx. 50 mm. Fixing apparatus: an oval carpal group of knobs and suckers, and 2 rows of alternating knobs and suckers on distal two thirds of stalk. No arm photophores in mature females. Ends of all arms elongated in mature males, ends of 2nd-3rd arms modified, with 2 rows of abruptly reduced suckers. Medial component of funnel organ with three conical papillae. Funnel valve absent. Two photophores on eyeball, a small elongate-oval anterior and a large crescent-shaped posterior.
Larvae semitransparent with dispersed red-brown chromatophores, adults dark purple-brown. ML up to 200-225 cm, weight up to 150 kg. Larvae identifiable by wide spindle-shaped mantle. Tubercles at mantle-to-head and mantle-to-funnel fusion sites appear in larvae at ML approx. 15 mm, eyes not stalked at ML >40-45 mm.
One species, rarely found northward of the Antarctic Convergence but occasionally reaching approx. 40°S.