Portal:Sharks

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Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorpha (or Selachii) and are the sister group to the Batoidea (rays and kin). Some sources extend the term "shark" as an informal category including extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as Cladoselache and Doliodus first appeared in the Devonian Period (419–359 million years), though some fossilized chondrichthyan-like scales are as old as the Late Ordovician (458–444 million years ago). The oldest modern sharks (selachimorphs) are known from the Early Jurassic, about 200 million years ago.

Sharks range in size from the small dwarf lanternshark (Etmopterus perryi), a deep sea species that is only 17 centimetres (6.7 in) in length, to the whale shark (Rhincodon typus), the largest fish in the world, which reaches approximately 12 metres (40 ft) in length. They are found in all seas and are common to depths up to 2,000 metres (6,600 ft). They generally do not live in freshwater, although there are a few known exceptions, such as the bull shark and the river shark, which can be found in both seawater and freshwater. Sharks have a covering of dermal denticles that protects their skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth.

Several species are apex predators, which are organisms that are at the top of their food chain. Select examples include the tiger shark, blue shark, great white shark, mako shark, thresher shark, and hammerhead shark. (Full article...)

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The finetooth shark, Carcharhinus isodon, is a species of requiem shark, family Carcharhinidae, found in the western Atlantic Ocean from North Carolina to Brazil. It forms large schools in shallow, coastal waters and migrates seasonally following warm water. A relatively small, slender-bodied shark, the finetooth shark can be identified by its needle-like teeth, dark blue-gray dorsal coloration, and long gill slits. It attains a maximum length of 1.9 m (6.2 ft). The diet of this species consists primarily of small bony fishes, in particular menhaden. Like other members of its family, it is viviparous in reproduction; every other year, females give birth to 2–6 pups in estuarine nursery areas. The finetooth shark is important to the gillnet shark fishery operating off the southeastern United States; the meat is sold for human consumption. Its population has not yet been depleted, but the US National Marine Fisheries Service (NMFS) has determined that fishing is occurring at unsustainable levels.

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Did you know (auto-generated)

... that since 2018, IKEA's stuffed toy shark Blåhaj has become a popular Internet meme and an icon of the online transgender community?
... that the greeneye spurdog, Sydney skate, grey skate and whitefin swellshark are at risk of extinction by trawling, according to a 2021 report?
... that the ampullae of Lorenzini enable sharks to sense electric fields?
... that Hixxy and Sharkey created a schism in the UK rave music scene in 1995?
... that Alexis Sharkey's last Instagram post before her murder documented her travels to Tulum, Mexico?
... that "the Hurricane Shark is real"?

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Credit: Didier Descouens

The jaw of a shortfin mako shark. The species feeds mainly upon cephalopods, bony fishes including mackerel, tuna, bonito, and swordfish, but it may also eat other sharks, porpoises, sea turtles, and seabirds.

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... that the spadenose shark exhibits the most advanced form of placental reproduction in fishes?
... that the dark, puffadder, brown, and Natal shysharks of South Africa are so named because they curl into a ring when threatened and "shyly" cover their eyes with their tails?
... that the daggernose shark can adjust the timing of events in its reproductive cycle by several months?
... that the lollipop catshark is shaped like a tadpole and has an almost gelatinous body?
... that the Australian swellshark can survive out of water for more than a day?

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General images

The following are images from various shark-related articles on Wikipedia.

Image 1Postural configuration of a Gray Reef Shark as it displays agonistic behaviour, in a sculpture (from Shark agonistic display)
Image 2The whale shark, the world's largest fish, is classified as Endangered.

Binding legislation and harvest management strategies... are urgently needed to address the disproportionate impact of fisheries on cartilaginous fishes.
– IUCN global study 2010
(from List of threatened sharks)
Image 3Dorsal fin diagram with landmarks labeled. (from Shark anatomy)
Image 4In a milestone decision in 2013, CITES prohibited international trade in the fins of the scalloped hammerhead (pictured) and four other shark species. (from List of threatened sharks)
Image 5Placoid Scale (from Shark anatomy)
Image 6The gill slits of a whale shark flaring as it expels water from its pharyngeal cavity. (from Shark anatomy)
Image 7A dissected view of the unique four-chambered heart of the sharkChambers: Sinus Venosus, Atrium, Ventricle, Conus Ateriosus (from Shark anatomy)
Image 8This grey reef shark demonstrates countershading, with its darker dorsal surface and lighter ventral surface. (from Shark anatomy)
Image 9Shark cage diving (from Shark tourism)
Image 10The major features of sharks (from Shark anatomy)
Image 11White shark cage diving near Gansbaai in South Africa (2015) (from Shark cage diving)
Image 12Great white shark cages at Isla Guadalupe, Mexico (from Shark cage diving)
Image 13BranchiostomaLanceolatum PioM (from Shark anatomy)
Image 14Postural elements of the agonistic display of the Gray Reef Shark (from Shark agonistic display)
Image 15Anti-cull protesters on Perth's Cottesloe Beach in Western Australia in 2014 (from Shark culling)
Image 16Depiction of shark anatomy including eggs, pups, and the liver (from Shark anatomy)
Image 17Distribution of highly sensitive ampullae of Lorenzini across the shark's head and rostrum. (from Shark agonistic display)
Image 18Great white shark at Isla Guadalupe, Mexico, August 2006. Animal estimated at 11–12 feet (3.3 to 3.6 m) in length, age unknown. (from Shark tourism)
Image 19Clear agonistic behaviour observed in Great White Shark (from Shark agonistic display)
Image 20A sign at Pyramid Rock Beach in Hawaii warning about a shark sighting, 2015 (from Shark tourism)
Image 21Lateral and Cross Section View of Shark Red and White Locomotor Muscles (from Shark anatomy)
Image 22Shark Anatomy (50693674756) (from Shark anatomy)
Image 23Sharks swimming outside shark-proof cage with people inside. (from Shark cage diving)
Image 24A 14-foot (4.3 m), 1,200-pound (540 kg) tiger shark caught in Kāne'ohe Bay, Oahu, in 1966
Image 25A ventral dissection of a pregnant female dogshark exposing its internal gill slits and internal spiracles. (from Shark anatomy)
Image 26Sharksucker (Echeneis naucrates) (from Shark agonistic display)

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Topics

Shark · Outline of sharks

Shark orders

Carcharhiniformes (groundsharks) · Cladoselachiformes (extinct) · Eugeneodontida (extinct) · Heterodontiformes (bullhead sharks) · Hexanchiformes (most primitive sharks) · Hybodontiformes (extinct) · Iniopterygia (extinct) · Lamniformes (mackerel sharks) · Orectolobiformes (carpet sharks and relatives) · Pristiophoriformes (sawsharks and relatives) · Squaliformes (gulper sharks, bramble sharks, lantern sharks, rough sharks, sleeper sharks, dogfish sharks and relatives) · Squatiniformes (angel sharks) · Symmoriida (extinct) · Xenacanthida (also known as Xenacantiformes, extinct)

Major species