Hexanchiformes is the
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
consisting of the most primitive types of
sharkSharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago, before the time of the dinosaurs....
s, and numbering just five extant species.
FossilFossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record...
sharks that were apparently very similar to modern sevengill species are known from
JurassicThe Jurassic is a geologic period and system that extends from about Ma to Ma, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the "Age of Reptiles". The start of the period is marked by...
specimens.
Hexanchiformes is the
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
consisting of the most primitive types of
sharkSharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago, before the time of the dinosaurs....
s, and numbering just five extant species.
FossilFossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record...
sharks that were apparently very similar to modern sevengill species are known from
JurassicThe Jurassic is a geologic period and system that extends from about Ma to Ma, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the "Age of Reptiles". The start of the period is marked by...
specimens.
Hexanchiform sharks have only one
dorsal finA dorsal fin is a fin located on the backs of some fish, whales, dolphins, and porpoises, as well as the ichthyosaurs. Depending on the species, an animal can have up to three of them. Its main purpose is to stabilize the animal against rolling and assist in sudden turns...
, either six or seven
gill slitGill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...
s, and no
nictitating membraneThe nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten the eye while also keeping visibility...
in the eyes.
The frilled shark,
Chlamydoselachus anguineus, is very different from the
cow sharkCow sharks, or the Hexanchidae, are a family of sharks characterized by extra pairs of gill slits. There are probably only two seven-gilled genera, Heptranchias and Notoryhncus....
s, and it has been proposed that it be moved to its own order Chlamydoselachiformes.
Extant species
Family Chlamydoselachidae
- Chlamydoselachus
- Frilled shark, Chlamydoselachus anguineus (Garman
Samuel Walton Garman was a naturalist/ zoologist from Pennsylvania. He studied under Louis Agassiz. In 1868 he joined an expedition to the American West with John Wesley Powell. He was a friend and regular correspondent of the naturalist Edward Drinker Cope and in 1872 accompanied him on a fossil...
, 1884) http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=635&genusname=Chlamydoselachus&speciesname=anguineus
- Southern African frilled shark
The southern African frilled shark, Chlamydoselachus africana, is a species of shark in the family Chlamydoselachidae, described in 2009. It is found in deep water from off southern Angola to southern Namibia. This species is difficult to distinguish from the better-known frilled shark The southern...
, Chlamydoselachus africana
Family Hexanchidae (
cow sharkCow sharks, or the Hexanchidae, are a family of sharks characterized by extra pairs of gill slits. There are probably only two seven-gilled genera, Heptranchias and Notoryhncus....
s)
- Heptranchias
- Hexanchus
The sixgill sharks, Hexanchus, are a genus of deepwater sharks in the family Hexanchidae. These sharks are characterized by broad pointed heads, six pairs of gill slits, comb-like lower teeth, and a long tail...
- Bluntnose sixgill shark
The bluntnose sixgill shark, Hexanchus griseus, often simply called the cow shark, is the largest hexanchoid shark, growing to more than 5.4 m in length.-Taxonomy:...
, Hexanchus griseus (BonnaterreAbbé Pierre Joseph Bonnaterre was a French naturalist who contributed sections on cetaceans, mammals, birds, reptiles, amphibians, and insects to the Tableau encyclopédique et méthodique...
, 1788)
- Bigeyed sixgill shark
The bigeyed sixgill shark, Hexanchus nakamurai, is found around the Strait of Florida, around Cuba and the Bahamas, East Africa and Madagascar, the Philippines, and Taiwan, at depths of between 90 to 600 m, usually on the bottom....
, Hexanchus nakamurai (Teng, 1962)
- Notorynchus
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 is an extinct species of shark. It was classified based on two relatively complete teeth and two isolated crowns. Due to the limited material available and its similarities to Chlamydoselachus fiedleri, it has been suggested that the criteria with which T...
- Thrinax baumgartneri
Thrinax baumgartneri is an extinct species of shark. It was classified based on two relatively complete teeth and two isolated crowns. Due to the limited material available and its similarities to Chlamydoselachus fiedleri, it has been suggested that the criteria with which T...
Pfeil, 1983
Family Hexanchidae
- Heptranchias
- Heptranchias ezoensis Applegate & Uyeno, 1968
- Heptranchias howelii (Reed, 1946)
- Heptranchias tenuidens (Leriche, 1938)
- Hexanchus
The sixgill sharks, Hexanchus, are a genus of deepwater sharks in the family Hexanchidae. These sharks are characterized by broad pointed heads, six pairs of gill slits, comb-like lower teeth, and a long tail...
- 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, 1979
Family ?Mcmurdodontidae
- Mcmurdodus
- Mcmurdodus featherensis White, 1968
- Mcmurdodus whitei Turner, & Young, 1987