Hexanchiformes This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Hexanchiformes".
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.
Family Chlamydoselachidae
Family Hexanchidae (cow sharks)
Family Heptranchidae
Family Hexanchidae
Family ?Mcmurdodontidae
