Oxynotus is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of shark

Shark

Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s in the order Squaliformes

Squaliformes

Squaliformes is an order of sharks that includes about 97 species in seven families.Members of the order have two dorsal fins, which usually possess spines, no anal fin or nictitating membrane, and five gill slits. In most other respects, however, they are quite variable in form and size...

, commonly known as the rough sharks. It is the only extant genus

Monotypic

In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

 in the family Oxynotidae. They live in deep waters in the Atlantic and western Pacific ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

s.

Rough sharks are small to medium in size, ranging from 49 centimetres (1.6 ft) to 150 centimetres (4.9 ft) in adult body length, depending on species. Their bodies are compressed, giving them a triangular cross-section. They have two large dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

s, each with a sharp spine, and with the first fin placed far forward above the head. Even more so than their relatives, the dogfish

Squaliformes

Squaliformes is an order of sharks that includes about 97 species in seven families.Members of the order have two dorsal fins, which usually possess spines, no anal fin or nictitating membrane, and five gill slits. In most other respects, however, they are quite variable in form and size...

es, they have rough and prickly skin. Unusually among sharks, they also possess a luminous

Bioluminescence

Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...

 organ.

Species

• Oxynotus bruniensis (Ogilby
  James Douglas Ogilby
  James Douglas Ogilby was an Australian ichthyologist.Ogilby was born in Belfast, Ireland, and was the son of zoologist William Ogilby. He received his education at Winchester College, England, and Trinity College, Dublin.Ogilby worked for the British Museum before joining the Australian Museum in...
  
  , 1893) (Prickly dogfish)
• Oxynotus caribbaeus Cervigón
  Fernando Cervigón
  Dr. Fernando Cervigón is a Venezuelan ichthyologist and marine biologist. He has discovered and described numerous species of fish including the Caribbean roughshark and is author of numerous works on fish and Venezuela's ocean environment including Los Peces Marinos de Venezuela. He is the...
  
  , 1961 (Caribbean roughshark)
• Oxynotus centrina (Linnaeus
  Carolus Linnaeus
  Carl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...
  
  , 1758) (Angular roughshark)
• Oxynotus japonicus Yano & Murofushi, 1985 (Japanese roughshark)
• Oxynotus paradoxus Frade, 1929 (Sailfin roughshark)