45 Fun Facts About Hard Sharks

Roughly how many teeth can a shark shed over its lifetime?

Some sharks shed 30,000+ teeth in a lifetime: the teeth sit in the gums rather than the jaw, and replacement rows move forward like a conveyor belt.

Sharks breathe through gill slits on each side of the body; how many does a shark have per side?

Sharks have five to seven gill slits per side, plus a ribless skeleton of cartilage and pectoral fins that are not fused to the head.

Which order, the ground sharks, includes hammerheads, catsharks and requiem sharks?

Carcharhiniformes, the ground sharks, is the largest shark order with over 270 species, including the hammerheads, catsharks and requiem sharks such as the bull shark.

The oldest total-group chondrichthyans, the spiny sharks or acanthodians, appeared in which period?

Acanthodians appeared in the Early Silurian, around 439 million years ago; isolated shark-like scales go back even further, to the Late Ordovician.

Cladoselache, an early shark, is famous for well-preserved fossils from which formation?

Cladoselache is known from superbly preserved Late Devonian fossils in the Cleveland Shale along Lake Erie in Ohio; oddly, no claspers have ever been found on any specimen.

Helicoprion, a Permian shark relative, is famous for what bizarre feature?

Helicoprion's name means spiral saw: it carried a spiral tooth whorl, a coil of teeth known from fossils found in Russia and Australia. Alexander Karpinsky named it in 1899.

Megalodon's jaws could exert a bite force of roughly what?

A 2008 study estimated megalodon's bite force at 108,500 to 182,200 newtons, among the strongest of any animal; it lived from about 23 to 3.6 million years ago.

What is the maximum known length of the dwarf lanternshark, the world's smallest shark?

The dwarf lanternshark reaches a maximum known length of about 20 cm; it is known only from the upper continental slopes off Colombia and Venezuela at 283 to 439 metres.

What is the largest reliably recorded length for a whale shark?

The largest confirmed whale shark measured 18.8 m (61.7 ft); the species' lifespan is estimated at 80 to 130 years.

The whale shark was first scientifically distinguished after a specimen was harpooned in 1828 where?

A 4.6 m specimen harpooned in Table Bay, South Africa, in April 1828 let military doctor Andrew Smith describe the species the following year.

How many filter pads does a whale shark use to strain plankton from the water?

A whale shark has 20 filter pads lining its gill arches; water drawn in through the huge mouth passes through them, leaving plankton and small fish behind.

Which is the second-largest living shark after the whale shark?

The basking shark is second only to the whale shark in size; its name comes from feeding at the surface as if sunbathing, straining plankton with bristle-like gill rakers.

The first megamouth shark ever seen was caught in November 1976 when it became tangled in what?

It happened off Kahuku, Hawaii, and fewer than 300 specimens have been recorded since.

What top speed can the shortfin mako, the fastest shark, reach in bursts?

The shortfin mako has been clocked at 74 km/h in bursts, the fastest of any shark; its genus name Isurus means equal tail, from the near-equal lobes of its caudal fin.

Which genus holds the true river sharks of northern Australia, New Guinea and the Ganges?

Glyphis is the genus of true river sharks, including the speartooth shark of northern Australia and New Guinea and the Ganges shark; unlike bull sharks they live mainly in fresh and brackish water.

The bull shark swims far up rivers; in Africa it is named after which great river?

It is the Zambezi shark in Africa and the Lake Nicaragua shark in Central America, because it thrives in warm, shallow and even brackish water.

Which shark ranks second only to the great white in recorded fatal attacks on humans?

The tiger shark is second only to the great white in recorded fatal attacks; it is nicknamed the garbage eater for the licence plates and tyres found in its stomach.

Of more than 500 shark species, how many account for double-digit tallies of fatal unprovoked attacks on humans?

Just three: the great white, tiger and bull shark. Worldwide there are only around 80 unprovoked attacks a year.

Who coined the great white's genus name Carcharodon in 1838?

Sir Andrew Smith coined Carcharodon in 1838, combining Greek words for sharp and tooth; Linnaeus had described the species as Squalus carcharias in 1758, and it is the genus's only living species.

What is the technical name for the flattened, T-shaped head of a hammerhead shark?

The cephalofoil spreads the eyes for better binocular vision and gives more room for electroreceptors; hammerheads unusually school by day and hunt alone at night.

Which plant makes up about 62% of the omnivorous bonnethead shark's gut contents?

Seagrass makes up about 62% of the bonnethead's gut contents, and it digests it; the bonnethead is also the only shark whose head shape differs between the sexes.

Which deep-sea shark, described in 1898, has pink skin and highly protrusible jaws?

The goblin shark, described by David Starr Jordan in 1898, has pink skin, a blade-like snout studded with ampullae of Lorenzini, and jaws that shoot forward; its lineage is some 125 million years old.

The frilled shark's gestation period can last how long?

Frilled shark gestation may last up to 3.5 years, the longest known for any vertebrate; it swallows prey whole with about 300 trident-shaped teeth and swims like an eel.

Which shark, recorded down to 3,675 m, is the deepest-living species known?

The Portuguese dogfish has been recorded at 3,675 m, deeper than any other shark; its eyes are tuned to spot the bioluminescence of prey in water sunlight never reaches.

Which is the largest luminous vertebrate on record?

The kitefin shark, mostly 1 to 1.4 m long with a reported maximum of 1.8 m, was shown in 2021 to glow, making it the largest luminous vertebrate known.

Cookiecutter bite marks have been found on which unusual man-made objects?

Cookiecutter bite marks have been found on submarines and sea cables, as well as on whales, fish and, occasionally, people. The cigar-shaped shark takes a round plug from each.

The word wobbegong is thought to come from Dharug, an Australian Aboriginal language, and means what?

Wobbegong means shaggy beard, referring to the fleshy lobes around the carpet shark's mouth; 12 species are recognised, mostly around Australia and Indonesia.

Thresher sharks use their tails, which can be as long as their bodies, to do what?

Threshers whip their scythe-like upper tail lobe to stun prey, slapping schooling fish before eating them; the common thresher, Alopias vulpinus, is also called the fox shark.

Which shark is the only one known to gulp air at the surface and store it in its stomach for buoyancy?

The sand tiger gulps air so it can hang near-neutrally buoyant and hunt motionless and quiet. Its embryos eat their siblings in the womb.

Zebra sharks are named for their striped juveniles; what pattern do the adults show instead?

Adults wear dark spots on pale skin, which is why they are also called Indo-Pacific leopard sharks. Only the young, under about 50 to 90 cm, have light stripes on brown.

Roughly how many pups can a blue shark produce in one litter?

Blue sharks bear litters of 25 to over 100 pups after a 9-to-12-month gestation; they migrate huge distances, such as from New England to South America.

How long is the gestation of the spiny dogfish, among the longest of any animal?

Spiny dogfish carry their young for 18 to 24 months, among the longest gestations of any vertebrate; they defend themselves with two mildly venomous spines in front of the dorsal fins.

Which vitamin was harvested from shark liver oil in a 1930s-40s fishery boom?

Shark liver oil is rich in vitamin A; a boom fishery for soupfin sharks and spiny dogfish supplied it from the late 1930s until synthetic vitamin A was commercialised around 1950.

Pilot fish accompany many sharks but prefer which species?

Pilot fish favour the oceanic whitetip, eating parasites and scraps from their host in return for protection; juveniles shelter under jellyfish and drifting weed instead.

Angelsharks of the genus Squatina are so flattened that they resemble what?

Angelsharks are flattened like rays, with wing-like pectoral fins, but their gill slits sit on the sides; they lie buried on the bottom as ambush predators, and several species are critically endangered.

Which paired sensory organs on a sawshark's snout distinguish it from a sawfish?

Sawsharks carry a pair of long barbels partway along the tooth-edged rostrum, used to feel for prey in sediment; sawfish, which are rays, lack barbels.

Ningaloo Reef, famous for whale shark aggregations, is how long?

Ningaloo Reef runs about 260 km along Western Australia's coast; it is Australia's largest fringing reef, and the Ningaloo Coast became a World Heritage Site in 2011.

Which treaty regulates international trade in great white, basking and whale shark parts via Appendix II?

CITES added the whale shark and basking shark to Appendix II in 2002 and the great white in 2004, so exports need permits showing the trade is sustainable.

Jaws was shot mostly on location on which island, becoming the first major film shot on the ocean?

Jaws was filmed on Martha's Vineyard, standing in for Amity Island; the mechanical sharks kept breaking, so Spielberg hid the shark and leaned on John Williams's two-note theme.

Who rewrote the Jaws script during filming after Peter Benchley's first drafts?

Carl Gottlieb, credited with Benchley, rewrote the script nightly during the shoot; the film starred Roy Scheider, Richard Dreyfuss and Robert Shaw and became the prototype summer blockbuster.

Discovery Channel's Shark Week premiered in which year?

Shark Week first aired on 17 July 1988 on Discovery Channel, originally as a week of conservation-minded documentaries.

Chondrichthyes splits into Elasmobranchii and which subclass, the chimaeras or ghost sharks?

Holocephali, the chimaeras or ghost sharks, is the sister subclass to the elasmobranchs; chimaeras have a single gill opening per side and an upper jaw fused to the skull.

The Devonian-Carboniferous shark relative Stethacanthus had a back fin shaped like what?

Stethacanthus's first dorsal fin rose into an anvil or ironing-board shape topped with tooth-like denticles; it seems to have been carried only by mature males, and the genus died out around 299 million years ago.

Remoras cling to sharks using a sucker formed from which modified fin?

The remora's sucker is its modified first dorsal fin, a flat oval of slat-like ridges; sliding backward tightens the grip and swimming forward releases it.

At roughly what age does a Greenland shark, the longest-lived vertebrate, reach sexual maturity?

Greenland sharks reach sexual maturity at about 150 years; a 2016 radiocarbon study put their lifespan at 272 to 512 years, and gestation may last 8 to 18 years.