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Cow sharks are a family, the Hexanchidae, of sharks characterized by an additional pair or pairs of gill slits. There are 37 species within the 10 genera Gladioserratus, Heptranchias, Hexanchus, Notidanodon, Notorynchus, Pachyhexanchus, Paraheptranchias, Pseudonotidanus, Welcommia, and Weltonia.

Cow sharks are considered the most primitive of all the sharks, as their skeletons resemble those of ancient extinct forms, with few modern adaptations. Their excretory and digestive systems are also unspecialised, suggesting they may resemble those of primitive shark ancestors.

Their most distinctive feature, however, is the presence of a sixth, and, in two genera, a seventh, gill slit, in contrast to the five found in all other sharks. They range from 1.4 to 5.5 m (4.6 to 18.0 ft) in adult body length.

Cow sharks are ovoviviparous, with the mother retaining the egg cases in her body until they hatch. They feed on relatively large fish of all kinds, including other sharks, as well as on crustaceans and carrion.

Species


Cow shark

The 37 species of cow shark, in 10 genera, are:

  • †Gladioserratus Underwood, Goswami, Prasad, Verma & Flynn, 2011
    • †Gladioserratus aptiensis Pictet, 1864
    • †Gladioserratus dentatus Guinot, Cappetta & Adnet, 2014
    • †Gladioserratus magnus Underwood, Goswami, Prasad, Verma & Flynn, 2011
  • Heptranchias Rafinesque, 1810
    • Heptranchias perlo (Bonnaterre, 1788) (Sharpnose sevengill shark)
    • †Heptranchias ezoensis Applegate & Uyeno, 1968
    • †Heptranchias howellii Reed, 1946
    • †Heptranchias karagalensis Kozlov in Zhelezko & Kozlov, 1999
    • †Heptranchias tenuidens Leriche, 1938
  • Hexanchus Rafinesque, 1810
    • Hexanchus griseus (Bonnaterre, 1788) (Bluntnose sixgill shark)
    • Hexanchus nakamurai Teng, 1962 (Bigeyed sixgill shark)
    • †Hexanchus agassizi Cappetta, 1976
    • †Hexanchus andersoni Jordan, 1907
    • †Hexanchus casieri Kozlov, 1999
    • †Hexanchus collinsonae Ward, 1979
    • †Hexanchus gracilis Davis, 1887
    • †Hexanchus hookeri Ward, 1979
    • †Hexanchus microdon Agassiz, 1843
    • †Hexanchus tusbairicus Kozlov in Zhelezko & Kozlov, 1999
  • †Notidanodon Cappetta, 1975
    • †Notidanodon brotzeni Siverson, 1995
    • †Notidanodon dentatus Woodward, 1886
    • †Notidanodon lanceolatus Woodward, 1886
    • †Notidanodon loozi Vincent, 1876
    • †Notidanodon pectinatus Agassiz, 1843
  • Notorynchus Ayres, 1855
    • Notorynchus cepedianus (Péron, 1807) (Broadnose sevengill shark)
    • †Notorynchus borealus Jordan & Hannibal, 1923
    • †Notorynchus kempi Ward, 1979
    • †Notorynchus lawleyi Cigala Fulgosi, 1983
    • †Notorynchus primigenius Agassiz, 1843
    • †Notorynchus serratissimus Agassiz, 1843
    • †Notorynchus subrecurvus Oppenheimer, 1907
  • †Pachyhexanchus Cappetta, 1990
    • †Pachyhexanchus pockrandti Ward & Thies, 1987
  • †Paraheptranchias Pfeil, 1981
    • †Paraheptranchias repens Probst, 1879
  • †Pseudonotidanus Underwood & Ward, 2004
    • †Pseudonotidanus semirugosus Underwood & Ward, 2004
  • †Welcommia Cappetta, 1990
    • †Welcommia bodeuri Cappetta, 1990
    • †Welcommia cappettai Klug & Kriwet, 2010
  • †Weltonia Ward, 1979
    • †Weltonia ancistrodon Arambourg, 1952
    • †Weltonia burnhamensis Ward, 1979

References


Cow shark

External links


Cow shark
  • ReefQuest Centre: Order Hexanchiformes: Cow Sharks




Cow shark

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