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 earliest confirmed modern sharks (selachimorphs) are known from the Early Jurassic around 200 million years ago, with the oldest known member being Agaleus, though records of true sharks may extend back as far as the Permian.

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 puffadder shyshark or happy Eddie, Haploblepharus edwardsii, is a species of catshark, family Scyliorhinidae, endemic to the temperate waters off South Africa. This common shark is found on or near the bottom in sandy or rocky habitats, from the intertidal zone to a depth of 130 m (430 ft). Typically reaching 60 cm (24 in) in length, the puffadder shyshark has a slender, flattened body and head. It is strikingly patterned with a series of dark-edged, bright orange "saddles" and numerous small white spots over its back. The Natal shyshark (H. kistnasamyi), formally described in 2006, was once considered to be an alternate form of the puffadder shyshark.

When threatened, the puffadder shyshark (and other members of its genus) curls into a circle with its tail covering its eyes, giving rise to the local names "shyshark" and "doughnut". It is a predator that feeds mainly on crustaceans, polychaete worms, and small bony fishes. This shark is oviparous and females deposit egg capsules singly or in pairs onto underwater structures. Harmless to humans, the puffadder shyshark is usually discarded by commercial and recreational fishers alike for its small size. It has been assessed as Near Threatened by the International Union for Conservation of Nature (IUCN), as its entire population is located within a limited area and could potentially be affected by a local increase in fishing pressure or habitat degradation.

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... that Timo Meier became the first player in San Jose Sharks franchise history to score five goals in one game when he was 25?
... 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 Hurricane Shark is real"?
... that the ampullae of Lorenzini enable sharks to sense electric fields?
... that Alexis Sharkey's last Instagram post before her murder documented her travels to Tulum, Mexico?
... that Hixxy and Sharkey created a schism in the UK rave music scene in 1995?

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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 Portuguese dogfish is the deepest-living shark known, found as far down as 3,675 m (2.284 mi)?
... that the single known specimen of the Irrawaddy river shark was generally dismissed as an abnormal bull shark until 2005?
... that the green lanternshark often preys on squid and octopus much larger than itself, which it may overwhelm by attacking in packs?
... that the barbeled houndshark is the only shark with a spherical placenta?
... that the cookiecutter shark may use the absence of bioluminescence to attract prey?

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General images

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

Image 1Postural elements of the agonistic display of the Gray Reef Shark (from Shark agonistic display)
Image 2Depiction of shark anatomy including eggs, pups, and the liver (from Shark anatomy)
Image 3Sharksucker (Echeneis naucrates) (from Shark agonistic display)
Image 4Anti-cull protesters on Perth's Cottesloe Beach in Western Australia in 2014 (from Shark culling)
Image 5White shark cage diving near Gansbaai in South Africa (2015) (from Shark cage diving)
Image 6The gill slits of a whale shark flaring as it expels water from its pharyngeal cavity. (from Shark anatomy)
Image 7Sharks swimming outside shark-proof cage with people inside (from Shark cage diving)
Image 8A sign at Pyramid Rock Beach in Hawaii warning about a shark sighting, 2015 (from Shark tourism)
Image 9This grey reef shark demonstrates countershading, with its darker dorsal surface and lighter ventral surface. (from Shark anatomy)
Image 10Great 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 11Clear agonistic behaviour observed in Great White Shark (from Shark agonistic display)
Image 12Lateral and cross section view of shark's red and white locomotor muscles (from Shark anatomy)
Image 13Placoid Scale (from Shark anatomy)
Image 14A dissected view of the unique four-chambered heart of the sharkChambers: Sinus Venosus, Atrium, Ventricle, Conus Ateriosus (from Shark anatomy)
Image 15BranchiostomaLanceolatum PioM (from Shark anatomy)
Image 16Shark cage diving (from Shark tourism)
Image 17A 14-foot (4.3 m), 1,200-pound (540 kg) tiger shark caught in Kāne'ohe Bay, Oahu, in 1966
Image 18A ventral dissection of a pregnant female dogshark exposing its internal gill slits and internal spiracles. (from Shark anatomy)
Image 19Postural configuration of a Gray Reef Shark as it displays agonistic behaviour, in a sculpture (from Shark agonistic display)
Image 20Distribution of highly sensitive ampullae of Lorenzini across the shark's head and rostrum. (from Shark agonistic display)
Image 21The 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 22Shark Anatomy (50693674756) (from Shark anatomy)
Image 23Great white shark cages at Isla Guadalupe, Mexico (from Shark cage diving)
Image 24In 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 25The major features of sharks (from Shark anatomy)
Image 26Dorsal fin diagram with landmarks labeled. (from Shark anatomy)

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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