Elasmobranchii is a subclass of Chondrichthyes or cartilaginous fish, including modern sharks, rays, skates, and sawfish. Members of this subclass are characterised by having five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins and small placoid scales on the skin. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The details of this jaw anatomy vary between species, and help distinguish the different elasmobranch clades. The pelvic fins in males are modified to create claspers for the transfer of sperm. There is no swim bladder; instead, these fish maintain buoyancy with large livers rich in oil.
Shark liver oil is an oil obtained from the livers of sharks. It has been used for centuries as a folk remedy to promote the healing of wounds and as a remedy for respiratory tract and digestive system problems. It is still promoted as a dietary supplement, and additional claims have been made that it can treat other maladies such as cancer, HIV, radiation sickness, swine flu, and the common cold. To date, none of these claims has been medically validated and shark liver oil (alone) is not a medication prescribed or utilized by American physicians. However, it is a component of some moisturizing skin lotions and hemorrhoid medications.
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 smallfin gulper shark or endeavour dogfish, is a medium-sized deepwater dogfish in the family Centrophoridae.
The mosaic gulper shark is a small rare deepwater dogfish, found in the Pacific Ocean around Honshū, Japan and the Hawaiian Islands at depths between 260 and 728 m. It is one of 13 described species in the genus Centrophorus.
The little gulper shark is a small, deepwater dogfish of the family Centrophoridae.
The birdbeak dogfish is a dogfish shark of the family Centrophoridae found in the Pacific Ocean around Honshū, Japan, southern Australia, New Zealand, and Chile, and in the Atlantic Ocean from Iceland south to the Cape of Good Hope.
The gulper shark is a long and slender dogfish usually about three feet in length generally found in deep, murky waters all around the world. It is a light grayish brown, paler ventrally, with a long snout and large greenish eyes. This deep water shark has two dorsal fins with long, grooved spines and the second dorsal fin smaller than the first. Its upper teeth are blade-like and lower have finely serrated edges. This tertiary consumer feeds on mainly fish such as bony fish, but also cephalopods such as squid and other invertebrates like crustaceans. The gulper shark is currently an endangered species mainly because of exploitation by humans and their abnormally long gestation period and low fecundity, preventing their population from recovering. Because of the depth of their habitat, they are considered little to no threat to humans.
The arrowhead dogfish is a small little known deepwater dogfish of the family Centrophoridae.
The longsnout dogfish is a little-known deepwater dogfish, found in the Atlantic and Indian Oceans from Namibia to Mozambique and in the South Pacific off southern Australia and New Zealand.
The longnose velvet dogfish is a sleeper shark of the family Somniosidae, found circumglobally in southern hemisphere subtropical seas, at depths of between 230 and 1,500 m. It reaches a length of 130 cm. It has a diet consisting of predominantly mesopelagic fishes and squids.
The roughskin spurdog is a dogfish of the family Squalidae, found circumglobally between latitudes 35°N and 35°S, at depths of between 200 metres (660 ft) and 600 metres (2,000 ft). It reaches a length of 1.2 metres (3.9 ft).
The ornate dogfish is dogfish shark which is not widely known. It is found in deepwater on the continental slopes of the Indian Ocean, the Arabian Sea and the Bay of Bengal, at depths between 520 and 1,260 m. Its length is up to 30 cm, and its reproduction is ovoviviparous.
The shortspine spurdog is a dogfish, a member of the family Squalidae, found on continental shelves off Japan in temperate waters, from the surface to 950 m. Its length is up to 75 cm.
The knifetooth dogfish, is a harmless sleeper shark of the family Somniosidae, found in the eastern Atlantic, from Scotland to Spain, Portugal, and Senegal, and the southwest Pacific from New Zealand, between latitudes 58°N and 15°N, at depths of between 200 and 1,600 m. Its length is up to 1.1 metres (3.6 ft).
The velvet dogfish, the only member of the genus Zameus, is a small sleeper shark of the family Somniosidae, found around the world between latitudes 64°N and 48°S, from the surface to 2,000 m.
The Hawaiian Lanternshark is a species of small squaliform shark in the family Etmopteridae.
