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 confirmed modern sharks (selachimorphs) are known from the Early Jurassic, about 200 million years ago, 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 blacknose shark, Carcharhinus acronotus, is a species of requiem shark, family Carcharhinidae, common in the tropical and subtropical waters of the western Atlantic Ocean. This species generally inhabits coastal seagrass, sand, or rubble habitats, with adults preferring deeper water than juveniles. A small shark typically measuring 1.3 m (4.1 ft) long, the blacknose shark has a typical streamlined "requiem shark" shape with a long rounded snout, large eyes, and a small first dorsal fin. Its common name comes from a characteristic black blotch on the tip of its snout, though this may be indistinct in older individuals.

Blacknose sharks feed primarily on small bony fishes and cephalopods, and in turn fall prey to larger sharks. Like other members of their family, they exhibit a viviparous mode of reproduction in which the developing embryos are sustained by a placental connection. The females give birth to 3–6 young in late spring or early summer either annually or biennually, after a gestation period of 8–11 months. This species is not known to attack humans, though it has been documented performing a threat display towards divers. It is of moderate commercial and recreational importance. The conservation status of this species has not been assessed by the International Union for Conservation of Nature (IUCN); in 2009, the US National Oceanic and Atmospheric Administration (NOAA) announced that populations of the blacknose shark off the United States are being overfished, and proposed new conservation measures.

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Did you know (auto-generated)

... that "the Hurricane Shark is real"?
... that Alexis Sharkey's last Instagram post before her murder documented her travels to Tulum, Mexico?
... that since 2018, IKEA's stuffed toy shark Blåhaj has become a popular Internet meme and an icon of the online transgender community?
... that Hixxy and Sharkey created a schism in the UK rave music scene in 1995?
... that the ampullae of Lorenzini enable sharks to sense electric fields?
... that Timo Meier became the first player in San Jose Sharks franchise history to score five goals in one game when he was 25?

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Credit: John Singleton Copley

Watson and the Shark, a 1778 oil-on-canvas painting by John Singleton Copley, depicts the rescue of Brook Watson from a shark attack in Havana, Cuba.

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... that the velvet belly lantern shark has proteins in its liver that can detoxify heavy metals such as cadmium, copper, mercury, and zinc?
... that at night, the Pacific angelshark may use bioluminescent plankton to target its prey?
... that the Galapagos shark is often the most abundant shark around oceanic islands?
... that the blotched catshark exhibits fluorescence, with spots that glow yellow under blue light?
... that the grey reef shark is the first shark species known to perform a threat display to warn off divers who are too close?

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General images

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

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