Cow shark
Encyclopedia
Cow sharks, or the Hexanchidae, are a family
of shark
s characterized by an additional pair or pairs of gill slit
s. There are currently known to be four species in three genera, Heptranchias, Hexanchus
and Notorynchus,.
Cow sharks are considered the most primitive of all the sharks, because their skeletons resemble those of ancient extinct forms, with few modern adaptations. Their excretory
and digestive systems are also unspecialised, suggesting that 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 addition to the five found in all other sharks. They range from 1.4 metres (4.6 ft) to over 5.5 metres (18 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.
There are just four species of cow shark, in three genera:
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of shark
Shark
Sharks 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....
s characterized by an additional pair or pairs of gill slit
Gill slit
Gill 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. There are currently known to be four species in three genera, Heptranchias, Hexanchus
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, yellow lower teeth, and a long tail. It can grow up to 5 m long and weigh over 600 kg...
and Notorynchus,.
Cow sharks are considered the most primitive of all the sharks, because their skeletons resemble those of ancient extinct forms, with few modern adaptations. Their excretory
Excretory system
The excretory system is a passive biological system that removes excess, unnecessary or dangerous materials from an organism, so as to help maintain homeostasis within the organism and prevent damage to the body. It is responsible for the elimination of the waste products of metabolism as well as...
and digestive systems are also unspecialised, suggesting that 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 addition to the five found in all other sharks. They range from 1.4 metres (4.6 ft) to over 5.5 metres (18 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.
There are just four species of cow shark, in three genera:
- Heptranchias Rafinesque, 1810
- Heptranchias perlo (BonnaterrePierre Joseph 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) (Sharpnose sevengill shark)
- Heptranchias perlo (Bonnaterre
- HexanchusHexanchusThe 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, yellow lower teeth, and a long tail. It can grow up to 5 m long and weigh over 600 kg...
Rafinesque, 1810- Hexanchus griseus (BonnaterrePierre Joseph 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) (Bluntnose sixgill shark) - Hexanchus nakamurai Teng, 1962 (Bigeyed sixgill shark)
- Hexanchus griseus (Bonnaterre
- Notorynchus AyresWilliam Orville AyresWilliam Orville Ayres was an American physician and ichthyologist. Born in Connecticut, he studied to become a doctor at Yale University School of Medicine....
, 1855- Notorynchus cepedianus (PéronFrançois PéronFrançois Auguste Péron was a French naturalist and explorer. He is credited with the first use of the term anthropology.-Explorations:...
, 1807) (Broadnose sevengill shark)
- Notorynchus cepedianus (Péron