Hexanchiformes

Taxobox
name = Hexanchiformes

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image_width = 250px
image_caption = Frilled shark, "Chlamydoselachus anguineus"
regnum = Animalia
phylum = Chordata
classis = Chondrichthyes
subclassis = Elasmobranchii
ordo = Hexanchiformes
ordo_authority = de Buen, 1926
subdivision_ranks = Families
subdivision = See text for families, genera and species

Hexanchiformes is the order consisting of the most primitive types of sharks, and numbering just five extant species. Fossil sharks that were apparently very similar to modern sevengill species are known from Jurassic specimens.(Allen, 45)

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.

Classification

Extant species

Family Chlamydoselachidae
* "Chlamydoselachus"
** Frilled shark, "Chlamydoselachus anguineus" (Garman, 1884) [http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=635&genusname=Chlamydoselachus&speciesname=anguineus] Family Hexanchidae (cow sharks)
* "Heptranchias"
** Sharpnose sevengill shark, "Heptranchias perlo" (Bonnaterre, 1788) [http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=636&genusname=Heptranchias&speciesname=perlo]
* "Hexanchus"
** Bluntnose sixgill shark, "Hexanchus griseus " (Bonnaterre, 1788)
** Bigeyed sixgill shark, "Hexanchus nakamurai" (Teng, 1962)
* "Notorynchus"
** Broadnose sevengill shark or spotted sevengill shark, "Notorynchus cepedianus " (Péron, 1807) [http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=2531&genusname=Notorynchus&speciesname=cepedianus]

Extinct species

Family Chlamydoselachidae
* "Chlamydoselachus"
** "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"
** "Thrinax baumgartneri" Pfeil, 1983Family Heptranchidae
* "Heptranchias"
** "Heptranchias ezoensis" Applegate & Uyeno, 1968
** "Heptranchias howelii" (Reed, 1946)
** "Heptranchias tenuidens" (Leriche, 1938)Family Hexanchidae
* "Hexanchus"
** "Hexanchus arzoensis" (Debeaumont, 1960)
** "Hexanchus agassizi" [http://www.sheppeyfossils.com/pages/hexanchus_agassizi.htm]
** "Hexanchus collinsonae " Ward, 1979
** "Hexanchus gracilis " (Davis, 1887) [http://home.tiscali.be/belgiansharkteeth/post_oligocene/sharks/hexachus.htm]
** "Hexanchus griseus “andersoni” “gigas”" (Bonaterre, 1788)
** "Hexanchus hookeri " Ward, 1979
** "Hexanchus microdon “agassizii”" (Agassiz, 1843)
** "Hexanchus nakamurai “vitulus”" Teng, 1962
* "Notidanoides"
* "Notidanodon"
** "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"
** "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"
** "Paraheptranchias repens" (Probst, 1879)
** "Paranotidanus “Eonotidanus” contrarius" (Munster, 1843)
** "Paranotidanus intermedius" (Wagner, 1861)
** "Paranotidanus munsteri" (Agassiz, 1843)
** "Paranotidanus serratus" (Fraas, 1855)
* "Pseudonotidanus"
** "Pseudonotidanus semirugosus" Underwood & Ward, 2004
* "Weltonia"
** "Weltonia ancistrodon" (Arambourg, 1952)
** "Weltonia burnhamensis" Ward, 1979Family ?Mcmurdodontidae
* "Mcmurdodus"
** "Mcmurdodus featherensis" White, 1968
** "Mcmurdodus whitei" Turner, & Young, 1987

ee also

* Time range of Hexanchiformes species

References

* Allen, Thomas B. "The Shark Almanac". New York: The Lyons Press, 1999. ISBN 1-55821-582-4