Gnathophis habenatus habenatus (Richardson, 1848) of shallow New Zealand coastal waters has the preanal region long, never less than 40% of total length, while Gnathophis h. longicaudatus (Ramsay & Ogilby, 1888) from Southeast Australia resembles the Japanese G. heterognathus and G. nystromi and the Californian G. catalinensis in a short preanal region, less than 40% of total length. Both subspecies have 120–129 vertebrae, scroll-like anterior nostrils and an inconspicuous, triangular premaxillary-ethmoid patch of teeth, distinct from G. incognitus n. sp., the adult as yet known only from New Zealand waters, which has 139–147 vertebrae, anterior nostril with a simple, free flap, externally obvious premaxillary-ethmoid patch of teeth, minute, scattered epidermal papillae and preanal region usually less than 40% of total length.

Size-range of leptocephali indicate spawning off New South Wales and Western Australia, metamorphosis at about 80mm and characteristically a posterior vent, somatic pigment as a ventral, regular series at the level of the simple intestine, small pigment crescent below iris and in the largest larvae, a pigment spot at the base of most anal rays.