Squaliformes is an order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 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 that includes about 97 species in seven families.

Members of the order have two 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, which usually possess spines, no anal fin or nictitating membrane

Nictitating membrane

The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...

, and five gill slit

Gill slit

Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...

s. In most other respects, however, they are quite variable in form and size. They are found worldwide, from polar to tropical waters, and from shallow coastal seas to the open ocean.

Classification

Family Centrophoridae

Centrophoridae

Centrophoridae are a family of squaliform sharks. The family contains just two genera and approximately 15 species. They are sometimes called gulper sharks but this is also the name of a specific species in the family, Centrophorus granulosus....

Bleeker

Pieter Bleeker

Pieter Bleeker was a Dutch medical doctor and ichthyologist, famous for his work on the fishes of East Asia – Atlas Ichthyologique des Orientales Neerlandaises – which was published 1862–1877....

, 1859 (gulper sharks)

• Genus Centrophorus
  Centrophorus
  Centrophorus is a genus of squaliform sharks. They are deep-water sharks found in temperate and tropical oceans throughout the world. They are characterized by grey or brown bodies, large green eyes, and spines on both dorsal fins...
  
  
• Genus Deania
  Deania
  Deania is a genus of long-snouted, deepwater dogfish sharks in the family Centrophoridae.-Species:* Deania calcea * Deania hystricosa * Deania profundorum Deania is a genus of long-snouted, deepwater dogfish sharks in the family Centrophoridae.-Species:* Deania calcea (R. T. Lowe, 1839) (Birdbeak...
  
  

Family Dalatiidae

Dalatiidae

Dalatiidae is a family of sharks in the order Squaliformes, commonly known as kitefin sharks . Members of this family are small, under long, and are found worldwide. They have cigar-shaped bodies with narrow heads and rounded snouts...

(J. E. Gray

John Edward Gray

John Edward Gray, FRS was a British zoologist. He was the elder brother of George Robert Gray and son of the pharmacologist and botanist Samuel Frederick Gray ....

, 1851) (kitefin sharks)

• Genus Euprotomicroides
• Genus Heteroscymnoides
• Genus Mollisquama
• Tribe Dalatiini
  • Genus Dalatias
  • Genus Isistius
    Isistius
    Isistius is a genus of dogfish sharks in the family Dalatiidae. They are commonly known as cookiecutter sharks. Members of the genus are known for their unusual behaviour and dentition.-Species:...
    
    
• Tribe Euprotomicrini
  • Genus Euprotomicrus
  • Genus Squaliolus
    Squaliolus
    Squaliolus is a genus of deep-sea dogfish sharks in the family Dalatiidae.-Species:* Squaliolus aliae Teng, 1959 * Squaliolus laticaudus H. M. Smith & Radcliffe, 1912...
    
    

Family Echinorhinidae Gill

Theodore Gill

Theodore Nicholas Gill was an American ichthyologist, mammalogist, malacologist and librarian.Born and educated in New York City under private tutors, Gill early showed interest in natural history. He was associated with J...

, 1862 (bramble sharks)

• Genus Echinorhinus
  Echinorhinus
  Echinorhinus is a genus of squaliform sharks, the only extant genus in the family Echinorhinidae. The name is from Greek echinos meaning "spiny" and rhinos meaning "nose". Both species are uncommon, little known sharks...
  
  

Family Etmopteridae

Etmopteridae

Etmopteridae is a family of sharks in the order Squaliformes, commonly known as lantern sharks. Their name comes from the presence of light-producing photophores on their bodies. The members of this family are small, under long, and are found in deep waters worldwide. There are 45 species in five...

Fowler

Henry Weed Fowler

Henry Weed Fowler was an American zoologist born in Holmesburg, Pennsylvania.He studied at Stanford University under David Starr Jordan...

, 1934 (lantern sharks)

• Genus Aculeola
• Genus Centroscyllium
  Centroscyllium
  Centroscyllium is a genus of big-eyed deepwater dogfishes with no anal fin, a grey or black-brown body, and dorsal spines, with the second one being much larger than the first. There are seven extant species.-Species:...
  
  
• Genus Etmopterus
  Etmopterus
  Etmopterus, commonly known as lantern sharks, is a diverse genus of dogfish sharks in the family Etmopteridae. This genus has 35 described species.-Species:* Etmopterus baxteri...
  
  
• Genus Miroscyllium
• Genus Trigonognathus

Family Oxynotidae Gill

Theodore Gill

Theodore Nicholas Gill was an American ichthyologist, mammalogist, malacologist and librarian.Born and educated in New York City under private tutors, Gill early showed interest in natural history. He was associated with J...

, 1872 (rough sharks)

• Genus Oxynotus
  Oxynotus
  Oxynotus is a genus of sharks in the order Squaliformes, commonly known as the rough sharks. It is the only extant genus in the family Oxynotidae. They live in deep waters in the Atlantic and western Pacific oceans....
  
  

Family Somniosidae

Somniosidae

Somniosidae is a family of sharks in the order Squaliformes, commonly known as sleeper sharks.-Genera:* Centroscymnus Barbosa du Bocage & Brito Capello, 1864...

D. S. Jordan

David Starr Jordan

David Starr Jordan, Ph.D., LL.D. was a leading eugenicist, ichthyologist, educator and peace activist. He was president of Indiana University and Stanford University.-Early life and education:...

, 1888 (sleeper sharks)

• Genus Centroscymnus
  Centroscymnus
  Centroscymnus is a genus of squaliform sleeper sharks in the family Somniosidae.-Species:* Centroscymnus coelolepis...
  
  
• Genus Centroselachus
• Genus Proscymnodon
  Proscymnodon
  Proscymnodon is a genus of fish in the Somniosidae family.It contains the following species:* Proscymnodon macracanthus * Proscymnodon plunketi...
  
  
• Genus Scymnodalatias
  Scymnodalatias
  Scymnodalatias is a genus of squaliform sharks in the family Somniosidae.-Species:* Scymnodalatias albicauda Taniuchi & Garrick, 1986 * Scymnodalatias garricki Kukuyev & Konovalenko, 1988...
  
  
• Genus Scymnodon
  Scymnodon
  Scymnodon is a genus of squaliform sharks in the family Somniosidae.-Species:** Scymnodon obscurus ** Scymnodon ringens Barbosa du Bocage & Brito Capello, 1864...
  
  
• Genus Somniosus
  Somniosus
  Somniosus is a genus of dogfish sharks in the family Somniosidae.-Species:* Somniosus microcephalus * Somniosus pacificus Bigelow & Schroeder, 1944...
  
  
• Genus Zameus
  Zameus
  Zameus is a genus of dogfish shark in the family Somniosidae, containing two species.-Species:* Zameus ichiharai * Zameus squamulosus...
  
  

Family Squalidae

Squalidae

Squalidae is the family of dogfish sharks. They are found in the Atlantic, Pacific, and Indian oceans, from tropical equatorial climates to the Arctic and Antarctic....

Blainville

Henri Marie Ducrotay de Blainville

Henri Marie Ducrotay de Blainville was a French zoologist and anatomist.Blainville was born at Arques, near Dieppe. In about 1796 he went to Paris to study painting, but he ultimately devoted himself to natural history, and attracted the attention of Georges Cuvier, for whom he occasionally...

, 1816 (dogfish sharks)

• Genus Cirrhigaleus
  Cirrhigaleus
  Cirrhigaleus is a genus of squaliform sharks in the family Squalidae.-Species:* Cirrhigaleus asper * Cirrhigaleus australis W. T. White, Last & Stevens, 2007...
  
  
• Genus Squalus

Further reading

• FAO Species catalogue Volume 4 Parts 1 and 2