ORDER-HEXANCHIFORMES
Kingdom: Animalia
Phylum: Chordata
Subclass: Elasmobranchii
Infraclass: Euselachii
Superorder: Selachimorpha
The order Hexanchiformes contains two families. The Frilled sharks, or Chlamydoselachidae, and the Cow sharks, or Hexanchidae.
These sharks can be found all over the world in tropical, temperate and boreal waters. They prefer deep, cold habitats mostly in the tropics. However, they can be found inshore in temperate temperatures as well.
Hexanchiformes typically have 6 or 7 gill slits. Their vertebral column extends all the way to the caudal fin’s long dorsal lobe. They have one spineless dorsal fin over or behind the pelvic fins. There is an anal fin present.
They have large mouths, and eyes positioned on the side of the head, with small spiracles above and behind the eyes. They do not have nictitating membranes.
The Frilled and Cow sharks are very different, and some scientists have proposed to separate the two into their own unique orders. However, this hasn’t been accepted.
Most of the families and species belonging to the order Hexanchiformes are quite primitive, and extinct. Most fossils of extinct species are traced back from Jurassic, Devonian and Permian periods. Shark teeth similar to those modern Hexanchids are known from Devonian deposits in Antarctica and Australia, as well as Permian deposits in Japan. If these are in fact Hexanchids, this may be the only extant order of elasmobranchs to have survived after the Permian extinction (and by extension, the oldest extant order of elasmobranchs) Below is a list of both living and extinct families. Visit our Primitive Sharks’ section in the Planet Shark Diver’s Academy to learn more of some of these families and species.
Living Families:
Chlamydoselachidae: Frilled Sharks
Extinct Families:
Chlamydoselachidae
Chlamydoselachus Garman, 1884
Chlamydoselachus bracheri Pfeil, 1983
Chlamydoselachus fiedleri Pfeil, 1983
Chlamydoselachus garmani Welton, 1983
Chlamydoselachus goliath Antunes & Cappetta, 2002
Chlamydoselachus gracilis Antunes & Cappetta, 2002
Chlamydoselachus keyesi Mannering & Hiller, 2008
Chlamydoselachus landinii Carrillo-Briceño, Aguilera & Rodriguez, 2014
Chlamydoselachus lawleyi Davis, 1887
Chlamydoselachus tatere Consoli, 2008
Chlamydoselachus thomsoni Richter & Ward, 1990
Chlamydoselachus tobleri Leriche, 1929
Proteothrinax Pfeil, 1983
Proteothrinax baumgartneri Pfeil, 1983
Crassonotidae
Crassodontidanus Kriwet & Klug, 2011
Crassodontidanus serratus Fraas, 1855
Crassodontidanus wiedenrothi Thies, 1983
Notidanoides Maisey, 1986
Notidanoides muensteri Agassiz, 1843
Notidanus Cuvier, 1816
Notidanus amalthei Oppel, 1854
Notidanus atrox Ameghino, 1899
Notidanus intermedius Wagner, 1862
Notidanus nikitini Chabakov & Zonov, 1935
Pachyhexanchus Cappetta, 1990
Pachyhexanchus pockrandti Ward & Thies, 1987
Hexanchidae
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 ezoensis Applegate & Uyeno, 1968
Heptranchias howellii Reed, 1946
Heptranchias karagalensis Kozlov in Zhelezko & Kozlov, 1999
Heptranchias tenuidens Leriche, 1938
Hexanchus Rafinesque, 1810
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 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
Mcmurdodontidae ?
Mcmurdodus featherensis White, 1968
Mcmurdodus whitei Turner, & Young, 1987
Orthacodontidae
Occitanodus Guinot, Cappetta & Adnet, 2014
Occitanodus sudrei Guinot, Cappetta & Adnet, 2014
Orthacodus Woodward, 1889
Orthacodus longidens Agassiz, 1843
Sphenodus Agassiz, 1843
Sphenodus alpinus Gümbel, 1861
Sphenodus longidens Agassiz, 1843
Sphenodus lundgreni Davis, 1890
Sphenodus macer Quenstedt, 1852
Sphenodus nitidus Wagner, 1862
Sphenodus planus Agassiz, 1843
Sphenodus rectidens Emmons, 1858
Sphenodus robustidens Seguenza, 1900
Sphenodus tithonius Gemmellaro, 1871
Sphenodus virgai Gemmellaro, 1871