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Temporal range: Upper Cretaceous–Recent
|Sand tiger shark (Carcharias taurus)|
J. P. Müller & Henle, 1839
Sand sharks, also known as sand tiger sharks, grey nurse sharks or ragged tooth sharks, are mackerel sharks of the family Odontaspididae. They are found worldwide in temperate and tropical waters. The three species are in two genera.
The body tends to be brown with dark markings in the upper half. These markings disappear as they mature. Their needle-like teeth are highly adapted for impaling fish, their main prey. Their teeth are long, narrow, and very sharp with smooth edges, with one and on occasion two smaller cusplets on either side. Sand sharks have a large second dorsal fin.The sand shark can grow up to 3.2 m (10.5 ft) long, and most adults can weigh around 200 kg (440 lb). The average lifespan of both sexes is only about 7 years, though they may live longer in captivity.
Location and origins
The name sand shark comes from their tendency toward shoreline habitats, and they are often seen swimming around the ocean floor in the surf zone; at times, they come very close to shore. They are often found in warm or temperate waters throughout the world's oceans, except the eastern Pacific. They also frequent the Mediterranean and Adriatic Seas at depths from 20 to 200 m (65 to 650 ft) and sometimes more. 
The sand shark has a unique hunting strategy. It is able to gulp air from above the surface and collect the air in its stomach. This enables them to become buoyant and approach their prey virtually motionless. During the day, the sand shark stays mostly inactive, but at night, it becomes active and resumes hunting activities. Their staple is small fish, but they will eat crustaceans and squid, as well. They occasionally hunt in groups, and have even been known to attack full fishing nets.
Sand sharks only develop two embryos, one in each uterus. The pups eat unfertilized eggs (oophagy) before being born. It has one of the lowest reproduction rates of all sharks and is susceptible to even minimal population pressure, so it is listed as vulnerable and is protected in much of its range.
Attacks on people
Sand sharks are not known to attack humans. If a person were to provoke a sand shark, it may retaliate defensively. Sand sharks are not aggressive. The size of the sand shark's mouth is not typically large enough to inflict traumatic wounds.
The family contains three species, in two genera:
- Genus Carcharias Rafinesque, 1810
- Genus Odontaspis Agassiz 183kc8
- Froese, Rainer, and Daniel Pauly, eds. (2009). "Odontaspididae" in FishBase. January 2009 version.
- Bigelow, Henry B.; Schroeder, William C. (1953). Fishes of the Gulf of Maine. United States Government Printing Office. Retrieved 30 October 2011.
- "Sand Tiger Shark Profile". National Geographic. National Geographic. Retrieved 17 May 2013.
- Carcharias taurus. Rafinesque, 1810. Sand tiger shark. FishBase
- Odontaspis ferox (Risso, 1810). Smalltooth sand tiger. FishBase
- Odontaspis noronhai (Maul, 1955). Bigeye sand tiger shark. FishBase
- FishBase Family Odontaspididae - Sand tigers. fishbase.org