Hexanchiformes

Hexanchiformes is the order consisting of the most primitive types of sharks, and numbering just six extant species. Fossil sharks that were apparently very similar to modern sevengill species are known from Jurassic specimens.

Hexanchiform sharks have only one dorsal fin, either six or seven gill slits, and no nictitating membrane in the eyes.

The frilled shark, Chlamydoselachus anguineus, is very different from the cow sharks, and it has been proposed that it be moved to its own order Chlamydoselachiformes.

Extant species

 * Family Chlamydoselachidae Garman 1884 (frilled sharks)
 * Chlamydoselachus Garman, 1884
 * Chlamydoselachus africana Ebert & Compagno, 2009 (Southern African frilled shark)
 * Chlamydoselachus anguineus Garman, 1884 (Frilled shark)
 * Family Hexanchidae J. E. Gray 1851 (cow sharks)
 * Heptranchias Rafinesque, 1810
 * Heptranchias perlo (Bonnaterre, 1788) (Sharpnose sevengill shark)
 * Hexanchus Rafinesque, 1810
 * Hexanchus griseus  (Bonnaterre, 1788) (Bluntnose sixgill shark)
 * Hexanchus nakamurai Teng, 1962 (Bigeyed sixgill shark)
 * Notorynchus Ayres, 1855
 * Notorynchus cepedianus  (Péron, 1807) (Broadnose sevengill shark)

Extinct species

 * Family Chlamydoselachidae
 * Chlamydoselachus Garman, 1884
 * Chlamydoselachus bracheri Pfeil, 1983
 * Chlamydoselachus gracilis Antunes & Cappetta, 2001
 * Chlamydoselachus goliath Antunes & Cappetta, 2001
 * Chlamydoselachus fiedleri Pfeil, 1983
 * Chlamydoselachus lawleyi Davis, 1887
 * Chlamydoselachus thomsoni Richter & Ward, 1990
 * Chlamydoselachus tobleri Leriche, 1929
 * Thrinax Pfeil, 1983
 * Thrinax baumgartneri Pfeil, 1983
 * Family Hexanchidae
 * Heptranchias Rafinesque, 1810
 * Heptranchias ezoensis Applegate & Uyeno, 1968
 * Heptranchias howelii (Reed, 1946)
 * Heptranchias tenuidens (Leriche, 1938)
 * Hexanchus Rafinesque, 1810
 * Hexanchus arzoensis (Debeaumont, 1960)
 * Hexanchus agassizi
 * Hexanchus collinsonae  Ward, 1979
 * Hexanchus gracilis  (Davis, 1887)
 * Hexanchus griseus “andersoni” “gigas” (Bonaterre, 1788)
 * Hexanchus hookeri  Ward, 1979
 * Hexanchus microdon “agassizii” (Agassiz, 1843)
 * Hexanchus nakamurai “vitulus” Teng, 1962
 * Notidanoides Maisey 1986
 * (No named species)
 * Notidanodon Cappetta, 1975
 * Notidanodon antarcti Grande & Chatterjee, 1987
 * Notidanodon brotzeni Siverson, 1995
 * Notidanodon dentatus (Woodward, 1886)
 * Notidanodon lanceolatus (Woodward, 1886)
 * Notidanodon loozi (Vincent, 1876)
 * Notidanodon pectinatus (Agassiz, 1843)
 * Notorynchus Ayres, 1855
 * Notorynchus aptiensis (Pictet, 1865)
 * Notorynchus intermedius Wagner
 * Notorynchus lawleyi Ciola & Fulgosi, 1983
 * Notorynchus munsteri (Agassiz, 1843)
 * Notorynchus serratissimus (Agassiz, 1844)
 * Notorynchus serratus (Agassiz, 1844)
 * Paraheptranchias PFEIL, 1981
 * Paraheptranchias repens (Probst, 1879)
 * Paranotidanus “Eonotidanus” contrarius (Munster, 1843)
 * Paranotidanus intermedius (Wagner, 1861)
 * Paranotidanus munsteri (Agassiz, 1843)
 * Paranotidanus serratus (Fraas, 1855)
 * Pseudonotidanus Underwood & Ward, 2004
 * Pseudonotidanus semirugosus Underwood & Ward, 2004
 * Weltonia Ward, 1979
 * Weltonia ancistrodon (Arambourg, 1952)
 * Weltonia burnhamensis Ward, 1979
 * Family ?Mcmurdodontidae
 * Mcmurdodus White, 1968
 * Mcmurdodus featherensis White, 1968
 * Mcmurdodus whitei Turner, & Young, 1987