The Velvet Belly Lanterns a species of dogfish shark in the family Etmopteridae. This species has virtually no commercial value, but large numbers are caught as bycatch in deepwater commercial fisheries. Although it has been assessed as of Least Concern by the International Union for Conservation of Nature, the heavy fishing pressure throughout its range and its slow reproductive rate are raising conservation concerns.
The velvet belly is a robustly built shark with a moderately long, broad, flattened snout. The mouth has thin, smooth lips. The upper teeth are small, with a narrow central cusp and usually fewer than three pairs of lateral cusplets. The lower teeth are much larger, with a strongly slanted, blade-like cusp at the top and interlocking bases. The five pairs of gill slits are tiny, comparable in size to the spiracles. Both dorsal fins bear stout, grooved spines at the front, with the second much longer than the first and curved. The first dorsal fin originates behind the short and rounded pectoral fins; the second dorsal fin is twice the size of the first and originates behind the pelvic fins. The anal fin is absent. The tail is slender, leading to a long caudal fin with a small lower lobe and a low upper lobe with a prominent ventral notch near the tip.
The dermal denticles are thin with hooked tips, arranged without a regular pattern well-separated from one another. The coloration is brown above, abruptly transitioning to black below. There are thin black marks above and behind the pelvic fins, and along the caudal fin. The velvet belly possesses numerous photophores that emit a blue-green light visible from 3–4 m (9.8–13 ft) away. Varying densities of photophores are arranged in nine patches on the shark's sides and belly, creating a pattern unique to this species: photophores are present along the lateral line, scattered beneath the head but excluding the mouth, evenly on the belly, and concentrated around the pectoral fins and beneath the caudal peduncle. The maximum reported length is 60 cm (24 in), although few are longer than 45 cm (18 in). Females are larger than males.
This shark mainly inhabits the outer continental and insular shelves and upper slopes over mud or clay, from close to the bottom to the middle of the water column. It is most common at a depth of 200–500 m (660–1,600 ft), though in the Rockall Trough, it is only found at a depth of 500–750 m (1,600–2,460 ft). This species has been reported from as shallow as 70 m (230 ft), and as deep as 2,490 m (8,170 ft).
As generalist predators, velvet bellies feed on crustaceans (e.g. pasiphaeid shrimp and krill), cephalopods (e.g. ommastrephid squid and sepiolids), and bony fishes (e.g. shads, barracudinas, lanternfishes, and pouts). Sharks off Italy also eat small amounts of nematodes, polychaete worms, and other cartilaginous fishes. Studies of velvet bellies off Norway and Portugal, and in the Rockall Trough, have found small sharks under 27 cm (11 in) long feed mainly on the krill Meganyctiphanes norvegica and the small fish Maurolicus muelleri. As the sharks grow larger, their diets become more varied, consisting mainly of squid and the shrimp Pasiphaea tarda, as well fishes other than M. muelleri. It has been speculated that smaller velvet bellies may be too slow to catch fast-moving cephalopods. The cephalopod diet of adults overlaps with that of the Portuguese dogfish; the latter species may avoid competition with the velvet belly by living in deeper water. The bite force exerted by the velvet belly is only around 1 N.