角鲨目目

此类鲨鱼虽多为栖息在深海的小型鲨鱼，但下属睡鲨属也有大型成员。

分类

• 角鲨目下分为7科，如下：
• 笠鳞鲛科 Echinorhinidae Gill, 1862
• 棘鲛科 Squalidae Blainville, 1816
• 尖鳍鲛科 Centrophoridae Bleeker, 1859
• 灯笼棘鲛科 Etmopteridae Fowler, 1934
• 梦棘鲛科 Somniosidae D. S. Jordan, 1888
• 粗皮棘鲛科 Oxynotidae Gill, 1872
• 黑棘鲛科 Dalatiidae J. E. Gray, 1851

The Squaliformes are an order of sharks that includes about 126 species in seven families.

Members of the order have two dorsal fins, which usually possess spines, they usually have a sharp head, no anal fin or nictitating membrane, and five to seven gill slits. In most other respects, however, they are quite variable in form and size. Most species of the squaliform order live in saltwater or brackish water. They are found worldwide, from northern to tropical waters, and from shallow coastal seas to the open ocean.

All members of the family Etmoperidae and Dalatiidae and Zameus squamulosus possess photophores, luminous organs, and exhibit intrinsic bioluminescence. Bioluminescence evolved once in Squaliformes, approximately 111–153 million years ago, and helped the Squaliformes radiate and adapt to the deep sea. The common ancestor of Dalatiidae, Etmopteridae, Somniosidae, and Oxynotidae possessed a luminous organ and used bioluminescence for camouflage by counterillumination. Counterillumination is an active form of camouflage in which an organism emits light to match the intensity of downwelling light to hide from predators below. Currently, bioluminescence provides different functions for Squaliformes based on the family. Dalatiidae and Zameus squamulosus possess simple photophores and use bioluminescence for ventral counter-illumination. Etmopteridae possess more complex photophores and utilize bioluminescence for ventral counter illumination as well as species recognition.

Many squaliforms have a spine in front of each of the two dorsal fins, likely a trait of the common ancestor of this clade. The clade likely originated in the post-Jurassic shallow waters of the northern Tethyal margin.

Classification

• Family Centrophoridae Bleeker, 1859 (gulper sharks)
• Genus Centrophorus
• Genus Deania
• Family Dalatiidae (J. E. Gray, 1851) (kitefin sharks)
• Genus Euprotomicroides
• Genus Heteroscymnoides
• Genus Mollisquama
• Genus Dalatias
• Genus Isistius
• Genus Euprotomicrus
• Genus Squaliolus
• Family Etmopteridae Fowler, 1934 (lantern sharks)
• Genus Aculeola
• Genus Centroscyllium
• Genus Etmopterus
• Genus Trigonognathus
• Family Oxynotidae Gill, 1872 (rough sharks)
• Genus Oxynotus
• Family Somniosidae D. S. Jordan, 1888 (sleeper sharks)
• Genus Centroscymnus
• Genus Centroselachus
• Genus Scymnodalatias
• Genus Scymnodon
• Genus Somniosus
• Genus Zameus
• Family Squalidae Blainville, 1816 (dogfish sharks)
• Genus Cirrhigaleus
• Genus Squalus