Portal:Sharks
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 earliest confirmed modern sharks (selachimorphs) 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 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 bull shark, tiger shark, great white shark, mako sharks, thresher sharks, and hammerhead sharks. (Full article...)
Selected article -
Measuring up to 3 m (10 ft) long, the Caribbean reef shark is one of the largest apex predators in the reef ecosystem, feeding on a variety of fishes and cephalopods. They have been documented resting motionless on the sea bottom or inside caves, unusual behavior for an active-swimming shark. If threatened, it may perform a threat display in which it frequently changes direction and dips its pectoral fins. Like other requiem sharks, it is viviparous with females giving birth to 4–6 young every other year. Caribbean reef sharks are of some importance to fisheries as a source of meat, leather, liver oil, and fishmeal, but recently they have become more valuable as an ecotourist attraction. In the Bahamas and elsewhere, bait is used to attract them to groups of divers in controversial "shark feedings". This species is responsible for a small number of attacks on humans.
Did you know (auto-generated)
- ... that "the Hurricane Shark is real"?
- ... 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?
- ... that a shark cost a competitor a silver medal in the spearfishing event at the 2014 Micronesian Games?
Categories
Related portals
WikiProjects
Selected picture -
More Did you know? -
- ... that the Portuguese dogfish is the deepest-living shark known, found as far down as 3,675 m (2.284 mi)?
- ... that the single known specimen of the Irrawaddy river shark was generally dismissed as an abnormal bull shark until 2005?
- ... that the green lanternshark often preys on squid and octopus much larger than itself, which it may overwhelm by attacking in packs?
- ... that the barbeled houndshark is the only shark with a spherical placenta?
- ... that the cookiecutter shark may use the absence of bioluminescence to attract prey?
General images
Topics
For additional lists of marine life-related featured articles and good articles see:
Wikimedia
The following Wikimedia Foundation sister projects provide more on this subject:
-
Commons
Free media repository -
Wikibooks
Free textbooks and manuals -
Wikidata
Free knowledge base -
Wikinews
Free-content news -
Wikiquote
Collection of quotations -
Wikisource
Free-content library -
Wikispecies
Directory of species -
Wikiversity
Free learning tools -
Wiktionary
Dictionary and thesaurus