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19-576: Sand sharks , also known as sand tiger sharks , gray 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

38-413: A monophyletic clade. This family is therefore polyphyletic and in need of revision. Lamniformes See text The Lamniformes ( / ˈ l æ m n ɪ f ɔːr m iː z / , from Greek lamna "fish of prey") are an order of sharks commonly known as mackerel sharks (which may also refer specifically to the family Lamnidae ). It includes some of the most familiar species of sharks, such as

57-412: A groove in their body when they swim. The shape, size, position and colour of the dorsal fin varies with the type of billfish, and can be a simple way to identify a billfish species. For example, the white marlin has a dorsal fin with a curved front edge and is covered with black spots. The huge dorsal fin, or sail, of the sailfish is kept retracted most of the time. Sailfish raise them if they want to herd

76-509: A large second dorsal fin . The sand shark can grow up to 3.2 m (10 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. The name sand shark comes from their tendency to migrate 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

95-413: A school of small fish, and also after periods of high activity, presumably to cool down. A dorsal fin is classified as a medial , unpaired fin that is located on the midline of the backs of some aquatic vertebrates. In development of the embryo in teleost fish, the dorsal fin arises from sections of the skin that form a caudal fin fold. The larval development and formation of the skeleton that support

114-788: A total of seven living families and 15 living species: Order Lamniformes Below is a cladogram showing relationships within Lamniformes. The topology of extant families is based on Vella & Vella (2020) and the placements of Cretoxyrhinidae and Otodontidae are based on Ferrón (2017), Cooper (2020), and Greenfield (2022). Mitsukurinidae [REDACTED] Alopiidae [REDACTED] Odontaspididae [REDACTED] Pseudocarchariidae [REDACTED] Megachasmidae [REDACTED] Carchariidae [REDACTED] Cetorhinidae [REDACTED] † Cretoxyrhinidae ? [REDACTED] † Otodontidae [REDACTED] Lamnidae [REDACTED] In 2010, Greenpeace International added

133-659: Is thus considered either the oldest lamniform or a sister group to all lamniforms. Lamniformes underwent a major adaptive radiation during the Cretaceous and became prominent elements of oceanic ecosystems. They reached their highest diversity during the Late Cretaceous, but severely declined during the K-Pg extinction , before rebounding to a high but lower diversity peak during the Paleogene . Lamniformes have severely declined over

152-405: Is to stabilize the animal against rolling and to assist in sudden turns. Some species have further adapted their dorsal fins to other uses. The sunfish uses the dorsal fin (and the anal fin ) for propulsion. In anglerfish , the anterior of the dorsal fin is modified into a biological equivalent to a fishing pole and a lure known as illicium or esca . Many catfish can lock the leading ray of

171-601: The World War II shipwrecks to dive with the sharks that make the wrecks their home. A recent report from the PEW Charitable Trusts suggests a new management approach used for large mammals that have suffered population declines could hold promise for sharks. Because of the life-history characteristics of sharks, conventional fisheries management approaches, such as reaching maximum sustainable yield , may not be sufficient to rebuild depleted shark populations. Some of

190-416: The great white as well as less familiar ones, such as the goblin shark and megamouth shark . Members of the order are distinguished by possessing two dorsal fins , an anal fin , five gill slits , eyes without nictitating membranes , and a mouth extending behind the eyes. Species in two families of Lamniformes – Lamnidae and Alopiidae – are distinguished for maintaining a higher body temperature than

209-454: The shortfin mako shark ( Isurus oxyrinchus ) to its seafood red list. Dorsal fin Wildlife biologists often use the distinctive nicks and wear patterns which develop on the dorsal fins of large cetaceans to identify individuals in the field. The bony or cartilaginous bones that support the base of the dorsal fin in fish are called pterygiophores . The main purpose of the dorsal fin

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228-402: The day, the sand shark stays mostly inactive, but at night, it becomes active and resumes hunting activities. Its staple is small fish, but it eats crustaceans and squid , as well. It occasionally hunts in shivers (groups), and has even been known to attack full fishing nets . Sand sharks only develop two embryos , one in each uterus. The largest and strongest embryos consume their siblings in

247-538: The dorsal fin in an extended position to discourage predation or to wedge themselves into a crevice. Some animals have developed dorsal fins with protective functions, such as spines or venom. For example, both the spiny dogfish and the Port Jackson shark have spines in their dorsal fins which are capable of secreting venom. Billfish have prominent dorsal fins. Like tuna, mackerel and other scombroids, billfish streamline themselves by retracting their dorsal fins into

266-498: The last 20 million years, with only 15 species alive today, compared to over 290 extant species in the Carcharhiniformes , which have evolved into medium and large body sizes during the same timeframe. The causes of the decline are uncertain, but are likely to have involved both biotic factors like competition and non-biotic factors like temperature and sea level. The order Lamniformes includes 10 families with 22 species, with

285-434: The median fins in adults result in pterygiophores. The skeletal elements of the pterygiophore includes basals and radials. The basals are located at the base of the dorsal fin, and are closest to the body. The radials extend outward from the body to support the rest of the fin. These elements serve as attachment sites for epaxial muscles. The muscles contract and pull against the basals of the pterygiophores along one side of

304-430: The more stringent approaches used to reverse declines in large mammals may be appropriate for sharks, including prohibitions on the retention of the most vulnerable species and regulation of international trade. The family contains three extant species, in two genera, as well as many extinct species in several genera. Recent mitochondrial DNA analysis of extant members has found the two extant members do not actually form

323-490: The surrounding waters. Members of the group include macropredators , generally of medium-large size, including the largest macropredatory shark ever, the extinct Otodus megalodon , as well as large planktivores . The small ~1 metre (3.3 ft) long carpet shark -like Palaeocarcharias , known from the Middle and Late Jurassic , shares the distinctive tooth histology of most lamniform sharks, which lack orthodentine, and

342-507: The womb ( intrauterine cannibalism ) before each surviving pup is 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. Sand sharks are not known to attack humans. If a person were to provoke a sand shark, it may retaliate defensively. Sand sharks are generally not aggressive, but harass divers who are spearfishing. In North America, wreck divers regularly visit

361-456: The world's oceans, except the eastern Pacific . They also frequent the Mediterranean and Adriatic Seas at depths from 20 to 200 m (66 to 656 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 it to become buoyant and approach its prey virtually motionless. During

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