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 Galapagos shark, Carcharhinus galapagensis, is a species of requiem shark, family Carcharhinidae, found worldwide. This species favors clear reef environments around oceanic islands, where it is often the most abundant shark species. A large species that grows to 3.7 m (12 ft), the Galapagos reef shark has a typical fusiform "reef shark" shape and is very difficult to distinguish from the dusky shark (C. obscurus) and the grey reef shark (C. amblyrhynchos). An identifying character of this species is its tall first dorsal fin, which has a slightly rounded tip and originates over the rear tips of the pectoral fins.

Galapagos sharks are active predators often encountered in large groups. They feed mainly on bottom-dwelling bony fishes and cephalopods; larger individuals have a much more varied diet, consuming other sharks, marine iguanas, sea lions, and even garbage. As in other requiem sharks, reproduction is viviparous, with females bearing litters of 4–16 pups every 2–3 years. The juveniles tend to remain in shallow water to avoid predation by the adults. Galapagos sharks are bold and have behaved aggressively towards humans, and are thus regarded as dangerous. The World Conservation Union has assessed this species as Near Threatened, as it has a slow reproductive rate and there is heavy fishing pressure across its range.

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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?

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Credit: Luc Viatour

The blacktip reef shark is a species of requiem shark, family Carcharhinidae, easily identified by the prominent black tips on its fins. It is among the most abundant sharks inhabiting the tropical coral reefs of the Indian and Pacific Oceans, and prefers shallow, inshore waters.

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

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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