The Squaliformes are an order of sharks that includes about 126 species in seven families.
Squalidae, more commonly known as dogfish, dog sharks, or spiny dogfish, are one of several families of sharks categorized under Squaliformes, making it the second largest order of sharks, numbering 119 species across 7 families. Having earned their name after a group of fishermen reportedly observed the species chasing down smaller fish in dog-like packs, dogfish have slender, streamlined bodies, usually more compact in comparison to other species, and a pointed snout. Dogfish likewise have two dorsal fins, each with smooth spines, but no anal fin, and their skin is generally rough to the touch. As the species reaches adulthood, males usually measure a maximum of 100 cm, while females typically measure 125 cm long. The species therefore exhibits female-dominant sexual dimorphism.
The cookiecutter shark, also called the cigar shark, is a species of small squaliform shark in the family Dalatiidae. This shark lives in warm, oceanic waters worldwide, particularly near islands, and has been recorded as deep as 3.7 km (2.3 mi). It migrates vertically up to 3 km (1.9 mi) every day, approaching the surface at dusk and descending with the dawn. Reaching only 42–56 cm (16.5–22 in) in length, the cookiecutter shark has a long, cylindrical body with a short, blunt snout, large eyes, two tiny spineless dorsal fins, and a large caudal fin. It is dark brown, with light-emitting photophores covering its underside except for a dark "collar" around its throat and gill slits.
The bramble shark is one of the two species of sharks in the family Echinorhinidae. Aside from the eastern Pacific Ocean, it is found in tropical and temperate waters worldwide. This rarely encountered shark swims close to the bottom of the seafloor, typically at depths of 400–900 m (1,300–3,000 ft), though it may enter much shallower water. The bramble shark has a stout body with two small dorsal fins positioned far back and no anal fin. It can be readily identified by the large, thorn-like dermal denticles scattered over its body, some of which may be fused together. It is purplish brown or black in color and grows up to 3.1 m (10 ft) long.
The dumb gulper shark is a rare and endangered deepwater dogfish, found along the east coast of Australia and in isolated spots north and west of New Zealand. It is also known as the dumb shark, Harrison's deep-sea dogfish, or Harrison's dogfish.
The bareskin dogfish is a little-known, deepwater dogfish shark of the family Etmopteridae. This species is found in the western Pacific from southern Japan to western and southeastern Australia as well as in New Zealand waters.
The kitefin shark or seal shark is a species of squaliform shark in the family Dalatiidae, and the type species in its genus. It is found sporadically around the world, usually close to the sea floor at depths of 200–600 m (660–1,970 ft). With a sizable oil-filled liver to maintain neutral buoyancy, this shark is able to cruise slowly through the water while expending little energy. The kitefin shark, the largest luminous vertebrate on record, has a slender body with a very short, blunt snout, large eyes, and thick lips. Its teeth are highly differentiated between the upper and lower jaws, with the upper teeth small and narrow and the lower teeth large, triangular, and serrated. Its typical length is 1.0–1.4 m (3.3–4.6 ft), though examples as long as 5.9 ft (180 cm) have been encountered.
The blackbelly lanternshark or lucifer shark is a shark of the family Etmopteridae found around the world in tropical and temperate seas at depths between 150 and 1,250 meters – the mesopelagic zone. Compared to other mesopelagic fish predators and invertebrates, the blackbelly lanternshark is thought to reside in shallower, more southern waters. E. lucifer can reach up to 47 centimeters in length and consumes mesopelagic cephalopods, fish, and crustaceans. Blackbelly lanternsharks are bioluminescent, using hormone controlled mechanisms to emit light through ventral photogenic organs called photophores and are presumed to be ovoviviparous. The blackbelly lanternshark has been classified as "Not Threatened" within the New Zealand Threat Classification System.
The New Zealand lanternshark is a shark of the family Etmopteridae mainly found off the coast of New Zealand. It can also be found in the Southern areas of Australia and Africa, inhabiting water depths between 500-1500m. These sharks can be commonly known as Baxter's dogfish and giant lantern shark. According to the New Zealand Threat Classification System (NZTCS), this species conservation status is considered non-threatened.
The taillight shark is a little-known species of shark in the family Dalatiidae and the only member of its genus. It is known from only four specimens collected from deep oceanic waters in the southern Atlantic Ocean and Pacific Ocean. A small shark with a laterally compressed body and a bulbous snout, this species has unusual adaptations that indicate a specialized lifestyle: its pectoral fins are paddle-like and may be used for propulsion, unlike other sharks and it has a pouch-like gland on its abdomen that emits clouds of luminescent blue fluid. This shark is likely aplacental viviparous and a formidable predator for its size.
The whitefin dogfish is a species of deep-sea dogfish shark in the family Etmopteridae. It has only been found in the northwest Pacific Ocean off the southeastern coast of Japan, between the latitudes of 35 and 32°N. It inhabits continental slopes and seamounts at a depth of 320 to 1,100 m. Reproduction is ovoviviparous. It is of no interest to fisheries and almost nothing is known of its biology. The specific epithet ritteri is in honor of Dr. William Emerson Ritter of the University of California.
The largetooth cookiecutter shark is a rare species of squaliform shark in the family Dalatiidae, reported from depths of 60–200 m (200–660 ft) at scattered locations in the Atlantic and Pacific Oceans. As its common name suggests, it is similar in appearance to the cookiecutter shark but has much larger lower teeth. This species reaches a maximum known length of 42 cm (17 in). The largetooth cookiecutter shark feeds by gouging out chunks of flesh from larger animals, including bony fishes, sharks, and marine mammals, and is able to take larger bites than I. brasiliensis. Little is known of its life history; it is thought to be a weaker swimmer than I. brasiliensis, and is presumably aplacental viviparous like the rest of its family. This shark is an infrequent bycatch of commercial trawl and longline fisheries, but is not thought to be much threatened by these activities.
The smalleye pygmy shark is a little-known species of squaliform shark in the family Dalatiidae, found in water 150–2,000 m (490–6,560 ft) deep near Japan, the Philippines, and Australia. It migrates vertically daily, spending the day in deep water and the night in shallower water. One of the smallest shark species, the smalleye pygmy shark is known to reach only 22 cm (8.7 in) long. It has a blackish, spindle-shaped body with relatively small eyes, and a spine preceding the first dorsal fin, but not the second. Bioluminescent photophores occur on its underside, which may serve to disguise its silhouette from predators. This species feeds on small squid, krill, shrimp, and bony fishes. It is aplacental viviparous. The International Union for Conservation of Nature has assessed it as Least Concern, citing its wide distribution and lack of threat from fisheries.
The Japanese roughshark is a rare species of shark in the family Oxynotidae, known only from a handful of specimens recovered from Suruga Bay and the Enshunada Sea off Japan. It is a benthic species that occurs at a depth of 150–350 m (490–1,150 ft). This shark is caught as bycatch by bottom trawlers throughout its entire limited range, and may be threatened given the declines in other bottom deep sea species in Suruga Bay.
The blurred lanternshark is a little-known species of dogfish shark in the family Etmopteridae, found around the world in benthic and pelagic habitats from a depth of 110 m (360 ft) to over 1 km (0.62 mi) down. This shark forms the E. pusillus species group with the smooth lanternshark, which are distinguished from other members of its family by having irregularly arranged, flat-topped dermal denticles that give them a "smooth" appearance. Both species are slender-bodied with long heads, two dorsal fins bearing spines, no anal fins, and light-emitting photophores. The blurred lanternshark is larger, reaching 67 cm (26 in) or more in length. This species feeds on small squid, fishes, and fish eggs, and is ovoviviparous. It has been assessed as of Least Concern by the International Union for Conservation of Nature, because of its wide distribution and lack of threat from fishing pressure.
The smooth lanternshark or slender lanternshark is a species of dogfish shark in the family Etmopteridae, found widely in the Atlantic and Pacific Oceans. It inhabits benthic environments at a depth of 274–1,000 m (899–3,281 ft), and pelagic environments at a depth of 0–708 m (0–2,323 ft). The smooth lanternshark forms a species group with the larger blurred lanternshark, both of which are distinguished from other members of their family by small, irregularly arranged dermal denticles with a truncated shape. This species has a slender, dark brown body with an indistinct black band on the sides over the pelvic fins, and reaches 50 cm (20 in) in length. This slow-growing, ovoviviparous shark feeds on smaller squid, fishes, and fish eggs. Smooth lanternsharks are often caught as bycatch in eastern Atlantic and Japanese commercial fisheries. The International Union for Conservation of Nature (IUCN) has evaluated this species as of Least Concern because of its wide distribution and limited threats.
The velvet belly lanternshark is a species of dogfish shark in the family Etmopteridae. One of the most common deepwater sharks in the northeastern Atlantic Ocean, the velvet belly is found from Iceland and Norway to Gabon and South Africa at a depth of 20–2,490 m (66–8,169 ft). A small shark generally no more than 45 cm (18 in) long, the velvet belly is so named because its black underside is abruptly distinct from the brown coloration on the rest of its body. The body of this species is fairly stout, with a moderately long snout and tail, and very small gill slits. Like other lanternsharks, the velvet belly is bioluminescent, with light-emitting photophores forming a species-specific pattern over its flanks and abdomen. The ventral photophores are thought to function in counter-illumination, which camouflages the shark against predators and prey. The bioluminescent flank markings may play a role in intraspecific communication.
The green lanternshark is a species of dogfish shark in the family Etmopteridae, found in the western central Atlantic Ocean. This species usually occurs on the upper continental slope below a depth of 350 m (1,150 ft). Reaching 26 cm (10 in) in length, the green lanternshark has a slender body with a long, thin tail and low, conical dermal denticles on its flanks. It is dark brown or gray with ventral black coloration, which contain light-emitting photophores that may serve a cryptic and/or social function. Green lanternsharks are thought to be gregarious and may attack their prey, squid and octopus often larger than themselves, in packs. Reproduction is aplacental viviparous, with females giving birth to litters of one to three young. This relatively common shark is an occasional, valueless bycatch of commercial fisheries; currently it does not appear to be significantly threatened by human activities.
The dwarf lanternshark is a species of dogfish shark in the family Etmopteridae and is the smallest shark in the world, reaching a maximum known length of 20 cm (8 in). It is known to be present only on the upper continental slopes off Colombia and Venezuela, at a depth of 283–439 m (928–1,440 ft). This species can be identified by its small size at maturity, long flattened head, and pattern of black ventral markings and a mid-dorsal line. Like other members of its genus, it is capable of producing light from a distinctive array of photophores. Reproduction is aplacental viviparous, with females gestating two or three young at a time. The dwarf lanternshark is not significant to commercial fisheries, but could be threatened by mortality from bycatch; the degree of impact from human activities on its population is unknown.
The brown lanternshark or bristled lanternshark is a little-known species of deep-sea dogfish shark in the family Etmopteridae. It is found off Japan and New Zealand, and possibly also South Africa and Australia, typically deeper than 300 m (980 ft). This species can be distinguished from other lanternsharks by its coloration, which is a uniform dark gray or brown without the ventral surface being much darker and clearly delineated from the rest of the body. The brown lanternshark feeds on small bony fishes, cephalopods, and crustaceans. Reproduction is ovoviviparous, with females giving birth to 9–18 young. An unusually high proportion of individuals in Suruga Bay are hermaphrodites, with both male and female characteristics.
