Portal:Sharks

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Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the division Selachii and are the sister group to the Batomorphi (rays and skates). 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 (Selachii) 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 sharks, which can be found in both seawater and freshwater, and the Ganges shark, which lives only in freshwater. Sharks have a covering of placoid scales (denticles) that protects the skin from damage and parasites in addition to improving their fluid dynamics. They have numerous sets of replaceable teeth.

Several shark species are apex predators, which are organisms that are at the top of their food chain with select examples including the bull shark, tiger shark, great white shark, mako sharks, thresher sharks and hammerhead sharks. Some sharks are filter-feeding planktivores, such as the whale shark and basking shark, which are among the largest fish ever lived. (Full article...)

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The Australian swellshark or draughtboard shark, Cephaloscyllium laticeps, is a species of catshark, family Scyliorhinidae, endemic to southern Australia. This bottom-dwelling species can be found on the continental shelf down to a depth of 220 m (720 ft). Usually measuring 1 m (3 ft) long, it is a stout-bodied, broad-headed shark with a short tail and a first dorsal fin much larger than the second. It can be identified by its variegated dorsal coloration of brown or gray patches and numerous spots.

Australian swellsharks are sedentary and mainly nocturnal, with most individuals remaining within the same local area throughout the year. It feeds on small crustaceans, cephalopods, and fishes. When threatened, it responds by rapidly taking in water or air to inflate its body, hence the name "swellshark". This shark is oviparous and females lay pairs of distinctively ridged egg capsules at 20–30 day intervals. The eggs hatch after 11–12 months. Harmless and of little commercial interest, many Australian swellsharks are caught incidentally in gillnets and bottom trawls but usually survive to be released because of their extreme hardiness. As a result, the International Union for Conservation of Nature (IUCN) has assessed this species as of Least Concern.

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... that a shark cost a competitor a silver medal in the spearfishing event at the 2014 Micronesian Games?
... 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 the parasitic copepod Driocephalus cerebrinoxius burrows into the brains of sharks through their noses?
... that Hixxy and Sharkey created a schism in the UK rave music scene in 1995?

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Credit: Zac Wolf

The whale shark is a slow moving filter feeding shark that is the largest living fish species. Four male and two female whale sharks are held in the Georgia Aquarium.

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... that the zebra shark is striped when young and spotted when mature?
... that the blurred and smooth lanternsharks form a species group distinguished from the rest of their family by the shape and arrangement of their dermal denticles?
... that the leopard shark feeds on anchovies by swimming into their schools with its mouth open and waiting for them to accidentally enter?
... that relative to its body size, the horn shark has the strongest known bite of any shark?
... that the title for Peter Benchley's best-selling 1974 novel Jaws was not agreed until 20 minutes before it went into production?

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General images

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

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