The Brown Lanternshark is a little-known species of deep-sea dogfish shark in the family Etmopteridae. An unusually high proportion of individuals in Suruga Bay are hermaphrodites, with both male and female characteristics.
The brown lanternshark has a robust, almost cylindrical body with a wide, flattened head. There are around 28 tooth rows in the upper jaw and 34 tooth rows in the lower jaw. The upper teeth have a pointed central cusp flanked by fewer than three pairs of lateral cusplets, while the bottom teeth are large and tipped with a strongly angled triangular cusp. The five pairs of gill slits are relatively large, about half as long as the eyes. The first dorsal fin is low with a minute leading spine; the second dorsal fin is twice as high as the first with a much larger spine. The caudal peduncle is short, leading to a long caudal fin with the upper lobe much larger than the lower.
The dermal denticles of this shark are tiny and densely placed with no regular pattern; each denticle has a four-cornered base and rises to a narrow, slightly curved point. The denticles of females are firmly attached, while those of males are easily removed. The coloration is a plain dark gray or brown, slightly darker below and lighter on the dorsal fin margins. Unlike other lanternsharks, there is a not a sharp contrast between the dorsal and ventral colors. There is a horizontal black line on the base of the tail, and another fainter black mark over the pelvic fins. The maximum reported length is 64 cm (25 in) for males and 75 cm (30 in) for females.
The brown lanternshark inhabits continental shelves and seamounts at a depth of 402–1,380 m (1,319–4,530 ft), though is most common below 900 m (3,000 ft). It is generally found deeper than other lanternsharks that share its range, and may have midwater habits.
The most important prey of the brown lanternshark are bony fishes (mainly lanternfishes), followed by cephalopods (mainly the squid Watasenia scintillans), and finally crustaceans (mainly prawns such as Acanthephyra).