Colonel William A. Phillips

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Welcome to the shark portal

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 milk shark, Rhizoprionodon acutus, is a species of requiem shark, family Carcharhinidae, whose common name comes from an Indian belief that consumption of its meat promotes lactation. The largest and most widely distributed member of its genus, the milk shark typically measures 1.1 m (3.6 ft) long and can be found in coastal tropical waters throughout the eastern Atlantic and the Indo-Pacific regions. Occurring from the surface to a depth of 200 m (660 ft), this species is common near beaches and in estuaries, and has been recorded swimming up rivers in Cambodia. Juveniles are known to inhabit tidal pools and seagrass meadows. The milk shark has a slender body with a long, pointed snout and large eyes, and is a nondescript gray above and white below. This shark can be distinguished from similar species in its range by the long furrows at the corners of its mouth, and 7–15 enlarged pores just above them.

Among the most abundant sharks within its range, the milk shark feeds primarily on small bony fishes but also takes cephalopods and crustaceans. In turn, it often falls prey to larger sharks and possibly marine mammals. In common with other members of its family, this species is viviparous with the developing embryos sustained by a placental connection. Females give birth to 1–8 young either during a defined breeding season or throughout the year, depending on location. The reproductive cycle is usually annual but may be biennial or triennial. Large numbers of milk sharks are caught by artisanal and commercial fisheries in many countries for meat, fins, and fishmeal. Despite this, the International Union for Conservation of Nature (IUCN) has assessed this species as being of Least Concern, because its wide distribution and relatively high productivity seemingly allow present levels of exploitation to be sustained.

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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 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 Hixxy and Sharkey created a schism in the UK rave music scene in 1995?
... that since 2018, IKEA's stuffed toy shark Blåhaj has become a popular Internet meme and an icon of the online transgender community?

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WikiProjects

WikiProjects related to sharks:

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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 taillight shark has a gland on its belly that releases clouds of luminescent blue fluid?
...that the Jersey Shore shark attacks of 1916 killed four people and inspired Peter Benchley's novel Jaws (1974)?
... that the presence of the rare bigeye sand tiger in the Pacific Ocean was first suspected based on teeth recovered from the ocean floor?
... that the rough skin of the nursehound was once used as an abrasive called "rubskin", which cost a hundred times more than sandpaper?
... that the epaulette shark can survive for an hour without oxygen?

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General images

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

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

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