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 smalltooth sand tiger or bumpytail ragged-tooth, Odontaspis ferox, is a species of sand shark, family Odontaspididae, with a patchy but worldwide distribution in tropical and warm temperate waters. They usually inhabit deepwater rocky habitats, though they are occasionally encountered in shallow water, and have been known to return to the same location year after year. This rare species is often mistaken for the much more common grey nurse shark (Carcharias taurus), from which it can be distinguished by its first dorsal fin, which is larger than the second and placed further forward. It grows to at least 4.1 m (13.5 ft) in length.

Very little is known of the biology and behavior of the smalltooth sand tiger. It is an active predator of benthic bony fishes, invertebrates, and cartilaginous fishes. This species is thought to be ovoviviparous with oophagous embryos like other mackerel sharks. In contrast to its formidable size and appearance, this shark is harmless, having never been known to behave aggressively towards humans. There is concern that its numbers are declining due to human activities in the Mediterranean and elsewhere, though existing data is inadequate for a full assessment of its conservation status.

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Did you know (auto-generated)

... that "the Hurricane Shark is real"?
... 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?
... 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?

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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 whitetip reef shark may have contributed to the Hawaiian myth of ʻaumākua, family guardian spirits, due to the "loyalty" of sharks that stay in the same area for years?
... that individual smalltooth sand tigers have been documented returning to the same location off Lebanon every summer?
...that Mustelus hacat is a species of smooth-hound shark discovered in 2003 in the Sea of Cortez, off the coast of Mexico?
... that during the summer the finetooth shark is found exclusively in water less than 10 m (30 ft) deep?
... that the Canary Islands are one of the few places left where there are still substantial numbers of angelsharks, once common all around Europe?
...that whilst most sharks are poikilothermic, species in the family Lamnidae are homeothermic?

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General images

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

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

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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