Hammerhead shark - wikipedia Hammerhead shark Hammerhead sharks Temporal range : Middle Miocene to Present PreЄ Є Pg Scalloped hammerhead, Sphyrna lewini Scientific classification Kingdom : Animalia Phylum : Chordata Class : Chondrichthyes Order : Carcharhiniformes Family : Sphyrnidae T.N. Gill, 1872 Genera Eusphyra Sphyrna The hammerhead sharks are a group of sharks in the family Sphyrnidae, so named for the unusual and distinctive structure of their heads, which are flattened and laterally extended into a `` hammer '' shape called a cephalofoil. Most hammerhead species are placed in the genus Sphyrna, while the winghead shark is placed in its own genus, Eusphyra. Many, but not necessarily mutually exclusive functions have been proposed for the cephalofoil, including sensory reception, manoeuvering, and prey manipulation. Hammerheads are found worldwide in warmer waters along coastlines and continental shelves. Unlike most sharks, hammerheads usually swim in schools during the day, becoming solitary hunters at night. Some of these schools can be found near Malpelo Island in Colombia, Cocos Island off Costa Rica, and near Molokai in Hawaii. Large schools are also seen in the waters off southern and eastern Africa. Contents 1 Description 2 Taxonomy and evolution 2.1 Cephalofoil 3 Reproduction 4 Diet 5 Species 6 Relationship with humans 6.1 In captivity 7 Protection 8 See also 9 References 10 External links Description Man carrying a hammerhead in the streets of Mogadishu ( Somalia ). The known species range from 0.9 to 6.0 m ( 3.0 to 19.7 ft ) in length and weigh from 3 to 580 kg ( 6.6 to 1,278.7 lb ). They are usually light gray and have a greenish tint. Their bellies are white which allows them to blend into the ocean when viewed from the bottom and sneak up on their prey. Their heads have lateral projections which give them a hammer - like shape. Hammerheads have disproportionately small mouths and seem to do a lot of bottom - hunting. They are also known to form schools during the day, sometimes in groups of over 100. In the evening, like other sharks, they become solitary hunters. National Geographic explains that hammerheads can be found in warm tropical waters, but during the summer, hammerheads participate in a mass migration to search for cooler waters. Taxonomy and evolution Since sharks do not have mineralized bones and rarely fossilize, their teeth alone are commonly found as fossils. The hammerheads seem closely related to the carcharhinid sharks that evolved during the mid-Tertiary period. According to DNA studies, the ancestor of the hammerheads probably lived in the Miocene epoch about 20 million years ago. Using mitochondrial DNA, a phylogenetic tree of the hammerhead sharks showed the winghead shark as its most basal member. As the winghead shark has proportionately the largest `` hammer '' of the hammerhead sharks, this suggests that the first ancestral hammerhead sharks also had large hammers. Cephalofoil The theory has been advanced that the hammer - like shape of the head may have evolved ( at least in part ) to enhance the animal 's vision. The positioning of the eyes, mounted on the sides of the shark 's distinctive hammer head, allows 360 degrees of vision in the vertical plane, meaning the animals can see above and below them at all times. The shape of the head was previously thought to help the shark find food, aiding in close - quarters maneuverability and allowing sharp turning movement without losing stability. However, it has been found that the unusual structure of its vertebrae was instrumental in making the turns correctly, more often than the shape of its head, though it would also shift and provide lift. From what is known about the winghead shark, the shape of the hammer - head apparently has to do with an evolved sensory function. Like all sharks, hammerheads have electroreceptory sensory pores called ampullae of Lorenzini. The pores on the shark 's head lead to sensory tubes, which detect electricity given off by other living creatures. By distributing the receptors over a wider area, like a larger radio antenna, hammerheads can sweep for prey more effectively. Reproduction Reproduction occurs only once a year for hammerhead sharks, and usually occurs with the male shark biting the female shark violently until she agrees to mate with him. The hammerhead sharks exhibit a viviparous mode of reproduction with females giving birth to live young. Like other sharks, fertilization is internal, with the male transferring sperm to the female through one of two intromittent organs called claspers. The developing embryos are at first sustained by a yolk sac. When the supply of yolk is exhausted, the depleted yolk sac transforms into a structure analogous to a mammalian placenta ( called a `` yolk sac placenta '' or `` pseudoplacenta '' ), through which the mother delivers sustenance until birth. Once the baby sharks are born, they are not taken care of by the parents in any way. Usually, a litter consists of 12 to 15 pups, except for the great hammerhead, which gives birth to litters of 20 to 40 pups. These baby sharks huddle together and swim toward warmer water until they are old enough and large enough to survive on their own. In 2007, the bonnethead shark was found to be capable of asexual reproduction via automictic parthenogenesis, in which a female 's ovum fuses with a polar body to form a zygote without the need for a male. This was the first shark known to do this. Diet Hammerhead sharks are known to eat a large range of prey such as fish ( including other sharks ), squid, octopus and crustaceans. Stingrays are a particular favorite. These sharks are often found swimming along the bottom of the ocean, stalking their prey. Their unique heads are used as a weapon when hunting down prey. The hammerhead shark uses its head to pin down stingrays and eats the ray when the ray is weak and in shock. The great hammerhead, tending to be larger and more aggressive than most hammerheads, occasionally engages in cannibalism, eating other hammerhead sharks, including its own young. In addition to the typical animal prey, bonnetheads have been found to feed on seagrass, it sometimes making up as much as half their stomach content. They may swallow it by incident, but studies show that they are able to partially digest it. This is the only known case of a potentially omnivorous species of shark. Species A Costa Rican hammerhead shark Species Common names IUCN status Eusphyra blochii Winghead shark Endangered Sphyrna corona Scalloped bonnethead Near threatened Sphyrna gilberti Carolina hammerhead Yet to be assessed Sphyrna lewini Scalloped hammerhead Endangered Sphyrna media Scoophead Data deficient Sphyrna mokarran Great hammerhead Endangered Sphyrna tiburo Bonnethead Least concern Sphyrna tudes Smalleye hammerhead Vulnerable Sphyrna zygaena Smooth hammerhead Vulnerable Relationship with humans A hammerhead shark at Atlantis Paradise Island According to the International Shark Attack File, humans have been subject to 17 documented, unprovoked attacks by hammerhead sharks within the genus Sphyrna since 1580 AD. There have been no recorded human fatalities. The great and the scalloped hammerheads are listed on the World Conservation Union 's ( IUCN ) 2008 Red List as endangered, whereas the smalleye hammerhead is listed as vulnerable. The status given to these sharks is as a result of overfishing and demand for their fins, an expensive delicacy. Among others, scientists expressed their concern about the plight of the scalloped hammerhead at the American Association for the Advancement of Science annual meeting in Boston, Massachusetts. The young swim mostly in shallow waters along shores all over the world to avoid predators. Shark fins are prized as a delicacy in certain countries in Asia ( such as China ), and overfishing is putting many hammerhead sharks at risk of extinction. Fishermen who harvest the animals typically cut off the fins and toss the remainder of the fish, which is often still alive, back into the sea. This practice, known as finning, is lethal to the shark. In Native Hawaiian culture, sharks are considered to be gods of the sea, protectors of humans, and cleaners of excessive ocean life. Some of these sharks are believed to be family members who died and have been reincarnated into shark form. However, some sharks are considered man - eaters, also known as niuhi. These sharks include great white sharks, tiger sharks, and bull sharks. The hammerhead shark, also known as mano kihikihi, is not considered a man - eater or niuhi ; it is considered to be one of the most respected sharks of the ocean, an aumakua. Many Hawaiian families believe that they have an aumakua watching over them and protecting them from the niuhi. The hammerhead shark is thought to be the birth animal of some children. Hawaiian children who are born with the hammerhead shark as an animal sign are believed to be warriors and are meant to sail the oceans. Hammerhead sharks rarely pass through the waters of Maui, but many Maui natives believe that hammerhead sharks swimming by is a sign that the gods are watching over the families, and the oceans are clean and balanced. In captivity The relatively small bonnethead is regular at public aquariums as it has proven easier to keep in captivity than the larger hammerhead species, and it has been bred at a handful of facilities. Nevertheless, at up to 1.5 m ( 5 ft ) in length and with highly specialized requirements, very few private aquarists have the experience and resources necessary to maintain a bonnethead in captivity. The larger hammerhead species can reach more than twice that size and are considered difficult, even compared to most other similar - sized sharks ( such as Carcharhinus species, lemon shark and sand tiger shark ) regularly kept by public aquariums. They are particularly vulnerable during transport between facilities, may rub on surfaces in tanks and may collide with rocks causing injuries to their head ; they therefore require very large specially adapted tanks. As a consequence, relatively few public aquariums have kept them for long periods. The scalloped hammerhead is the most frequently maintained large species and it has been kept long - term at public aquariums in most continents, but primarily in North America, Europe and Asia. In 2014, less than 15 public aquariums in the world kept scalloped hammerheads. Great hammerheads have been kept at a few facilities in North America, including Atlantis Paradise Island Resort ( Bahamas ), Adventure Aquarium ( New Jersey ), Georgia Aquarium ( Atlanta ), Mote Marine Laboratory ( Florida ), and the Shark Reef at Mandalay Bay ( Las Vegas ). Smooth hammerheads have also been kept in the past. Protection In March 2013, three endangered commercially valuable sharks, the hammerheads, the oceanic whitetip, and porbeagle, were added to Appendix II of CITES, bringing shark fishing and commerce of these species under licensing and regulation. See also Sharks portal For a topical guide to this subject, see Outline of sharks. List of prehistoric cartilaginous fish List of hammerhead sharks References Jump up ^ Sepkoski, Jack ( 2002 ). `` A compendium of fossil marine animal genera ( Chondrichthyes entry ) ''. Bulletins of American Paleontology. 364 : 560. Archived from the original on 2011 - 09 - 30. Jump up ^ Hessing, S. ( 2000 ). Sphyrna tiburo. Animal Diversity Web. Retrieved on 2012 - 12 - 19. Jump up ^ `` Record Hammerhead Pregnant With 55 Pups ''. Discovery News. Associated Press. July 1, 2006. Archived from the original on June 22, 2011. Retrieved October 18, 2008. Jump up ^ Hammerhead Shark. Sharks-world.com. Retrieved on 2012 - 12 - 19. Jump up ^ `` Hammerhead Shark ''. NationalGeographic.com. Retrieved November 9, 2016. Jump up ^ `` Hammerhead shark study shows cascade of evolution affected size, head shape ''. ScienceDaily.com. University of Colorado at Boulder. May 19, 2010. Retrieved November 9, 2016. Jump up ^ Martin, R. Aidan. `` Origin and Evolution of the ' Hammer ' ''. elasmo-research.org. Retrieved January 31, 2005. Jump up ^ McComb, D.M. ; Tricas, T.C. ; Kajiura, S.M. ( 2009 ). `` Enhanced visual fields in hammerhead sharks ''. Journal of Experimental Biology. 212 ( 24 ) : 4010. doi : 10.1242 / jeb. 032615. PMID 19946079. Jump up ^ McComb, D. Michelle ; et al. ( 2009 - 11 - 27 ). `` Hammerhead shark mystery solved ''. BBC News. Retrieved 2010 - 05 - 04. Jump up ^ `` World 's Deadliest : Hammerhead Sharks ''. video.nationalgeographic.com. Retrieved 2015 - 05 - 23. Jump up ^ Otfinoski, Steven ( 2000 ). Hammerheads and Other Sharks. World Book, Inc. p. 16. ISBN 0716612100. Jump up ^ Martin, R. Aidan ( August 1993 ). `` If I Had a Hammer ''. Rodale 's Scuba Diving. Retrieved March 31, 2006. ^ Jump up to : Hammerhead Shark. Aquatic Community. Retrieved on 2012 - 12 - 19. Jump up ^ Chapman, DD ; Shivji, MS ; Louis, E ; Sommer, J ; Fletcher, H ; Prodöhl, PA ( 2007 - 08 - 22 ). `` Virgin birth in a hammerhead shark ''. Biology Letters. 3 ( 4 ) : 425 -- 7. doi : 10.1098 / rsbl. 2007.0189. PMC 2390672. PMID 17519185. Jump up ^ `` Great hammerhead shark ''. EnchantedLearning.com. Enchanted Learning Software. Retrieved December 19, 2012. Jump up ^ Hannah Lang ( 29 June 2017 ). `` This Shark Eats Grass, and No One Knows Why ''. National Geographic. Jump up ^ `` Eusphyra blochii ( Slender Hammerhead, Winghead Shark ) ''. iucnredlist.org. Retrieved 2015 - 02 - 18. Jump up ^ `` Sphyrna corona ( crown shark, mallethead shark, scalloped bonnethead ) ''. iucnredlist.org. Retrieved 2015 - 08 - 30. Jump up ^ `` Catalogue of Life : Sphyrna gilberti Quattro, Driggers III, Grady, Ulrich & Roberts, 2013 ''. catalogueoflife.org. Retrieved 2015 - 08 - 30. Jump up ^ Baum, J., Clarke, S., Domingo, A., Ducrocq, M., Lamónaca, A.F., Gaibor, N., Graham, R., Jorgensen, S., Kotas, J.E., Medina, E., Martinez - Ortiz, J., Monzini Taccone di Sitizano, J., Morales, M.R., Navarro, S.S., Pérez - Jiménez, J.C., Ruiz, C., Smith, W., Valenti, S.V. & Vooren, C.M. ( 2007 ). Sphyrna lewini. The IUCN Red List of Threatened Species doi : 10.2305 / IUCN. UK. 2007. RLTS. T39385A10190088. en Jump up ^ Casper, B.M. & Burgess, G.H. ( 2006 ). Sphyrna media. The IUCN Red List of Threatened Species doi : 10.2305 / IUCN. UK. 2006. RLTS. T60201A12317805. en Jump up ^ Denham, J., Stevens, J., Simpfendorfer, C.A., Heupel, M.R., Cliff, G., Morgan, A., Graham, R., Ducrocq, M., Dulvy, N.D, Seisay, M., Asber, M., Valenti, S.V., Litvinov, F., Martins, P., Lemine Ould Sidi, M. & Tous, P. and Bucal, D. ( 2007 ). Sphyrna mokarran. The IUCN Red List of Threatened Species doi : 10.2305 / IUCN. UK. 2007. RLTS. T39386A10191938. en Jump up ^ Cortés, E., Lowry, D., Bethea, D. & Lowe, C.G. ( 2016 ). Sphyrna tiburo. The IUCN Red List of Threatened Species doi : 10.2305 / IUCN. UK. 2016 - 2. RLTS. T39387A2921446. en Jump up ^ Mycock, S.G., Lessa, R. & Almeida, Z. ( 2006 ). Sphyrna tudes. The IUCN Red List of Threatened Species doi : 10.2305 / IUCN. UK. 2006. RLTS. T60202A12318061. en Jump up ^ Casper, B.M., Domingo, A., Gaibor, N., Heupel, M.R., Kotas, E., Lamónaca, A.F., Pérez - Jimenez, J.C., Simpfendorfer, C., Smith, W.D., Stevens, J.D., Soldo, A. & Vooren, C.M. ( 2005 ). Sphyrna zygaena. The IUCN Red List of Threatened Species doi : 10.2305 / IUCN. UK. 2005. RLTS. T39388A10193797. en Jump up ^ `` Statistics on Attacking Species of Shark ''. Florida Museum of Natural History. Retrieved 2017 - 12 - 27. Jump up ^ `` Panamanian officials find half ton of shark fins ''. WashingtonPost.com. Associated Press. 2011 - 02 - 25. Jump up ^ Sharks Highly respected in Hawaiian Culture. Moolelo.com ( 2004 - 09 - 28 ). Retrieved on 2012 - 12 - 19. Jump up ^ Compagno, L. ; M. Dando & S. Fowler ( 2004 ). Sharks of the World. HarperCollins. p. 325. ISBN 0 - 00 - 713610 - 2. ^ Jump up to : Smith, M. ; D. Warmolts ; D. Thoney ; and R. Hueter, eds. ( 2004 ). Elasmobranch Husbandry Manual : Captive Care of Sharks, Rays, and their Relatives. Ohio Biological Survey, Inc. ISBN 9780867271522. CS1 maint : Uses editors parameter ( link ) Jump up ^ `` Babies Of The S.E.A. -- Bonnethead Shark ''. SEA Aquarium. Retrieved 2017 - 09 - 13. Jump up ^ `` The Bonnethead Shark Sphyrna tiburo : Is it Suitable for Home Aquariums ? ''. TFH MAagazine. September 2007. Retrieved 2017 - 09 - 13. ^ Jump up to : Tristram, H. ; S. Thomas ; and L. Squire - Junior ( 2014 ). `` Husbandry of scalloped hammerhead sharks Sphyrna lewini ( Griffith & Smith, 1834 ) at Reef HQ Aquarium, Townsville, Australia '' ( PDF ). Der Zoologische Garten. 83 ( 4 - 6 ) : 93 -- 113. doi : 10.1016 / j. zoolgart. 2014.08. 002. CS1 maint : Uses authors parameter ( link ) Jump up ^ `` Scalloped Hammerhead, Sphyrna lewini ( Griffith & Smith ) ''. elasmollet.org. Retrieved 2017 - 09 - 13. Jump up ^ `` Scalloped hammerhead shark ''. Zootierliste. Retrieved 2017 - 09 - 13. Jump up ^ `` Great Hammerheads, Sphyrna mokarran ( Rueppell, 1837 ) in Captivity ''. elasmollet.org. Retrieved 2015 - 12 - 17. Jump up ^ McGrath, Matt ( 11 March 2013 ). `` ' Historic ' day for shark protection ''. BBC News. Retrieved 27 July 2013. External links Wikimedia Commons has media related to Sphyrnidae. Froese, Rainer, and Daniel Pauly, eds. ( 2011 ). `` Sphyrnidae '' in FishBase. February 2011 version. Animal Diversity Web Genus Sphyrna with species sub-pages `` Electroreception in juvenile scalloped hammerhead and sandbar sharks '' by Stephen M. Kajiura and Kim N. Holland, The Journal of Experimental Biology ( 2002 ). Attempts to explain the `` hammer '' shape. Great hammerhead shark, Sphyrna mokarran, MarineBio.org `` New shark discovered in US waters ''. BBC News. 10 June 2006. Retrieved November 9, 2016. Extant ground shark species Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Chondrichthyes Subclass Elasmobranchii Subdivision Selachii Carcharhinidae ( Requiem sharks ) Large family not shown Hemigaleidae ( Weasel sharks ) Hemipristis Snaggletooth shark ( H. elongata ) Chaenogaleus Hooktooth shark ( C. macrostoma ) Hemigaleus Australian weasel shark ( H. australiensis ) Sicklefin weasel shark ( H. microstoma ) Paragaleus Whitetip weasel shark ( P. leucolomatus ) Atlantic weasel shark ( P. pectoralis ) Slender weasel shark ( P. randalli ) Straight - tooth weasel shark ( P. tengi ) Leptochariidae Leptocharias Barbeled houndshark ( L. smithii ) Proscylliidae ( Finback catsharks ) Ctenacis Harlequin catshark ( C. fehlmanni ) Eridacnis Cuban ribbontail catshark ( E. barbouri ) Pygmy ribbontail catshark ( E. radcliffei ) African ribbontail catshark ( E. sinuans ) Proscyllium Graceful catshark ( P. habereri ) Magnificent catshark ( P. magnificum ) P. venustum Pseudotriakidae Gollum Slender smooth - hound ( G. attenuatus ) Sulu gollumshark ( G. suluensis ) Planonasus Dwarf false catshark ( P. parini ) Pseudotriakis False catshark ( P. microdon ) Scyliorhinidae ( Catsharks ) Large family not shown Sphyrnidae ( Hammerhead sharks ) Eusphyra Winghead shark ( E. blochii ) Sphyrna Scalloped bonnethead ( S. corona ) Whitefin hammerhead ( S. couardi ) Carolina hammerhead ( S. gilberti ) Scalloped hammerhead ( S. lewini ) Scoophead ( S. media ) Great hammerhead ( S. mokarran ) Bonnethead ( S. tiburo ) Smalleye hammerhead ( S. tudes ) Smooth hammerhead ( S. zygaena ) Triakidae ( Houndsharks ) Large family not shown Taxon identifiers Wd : Q208490 ADW : Sphyrnidae EoL : 1895 EPPO : 1SPHYF Fossilworks : 83206 GBIF : 2207 ITIS : 160497 NCBI : 376648 WoRMS : 105694 BNF : cb14598630z ( data ) Retrieved from `` https://en.wikipedia.org/w/index.php?title=Hammerhead_shark&oldid=827116195 '' Categories : Sphyrnidae Vertebrate parthenogenesis Extant Miocene first appearances Species endangered by use as food Hidden categories : CS1 maint : Uses editors parameter CS1 maint : Uses authors parameter Articles with ' species ' microformats Wikipedia articles with BNF identifiers Talk Contents About Wikipedia Wikispecies Afrikaans Asturianu Беларуская Български བོད ་ ཡིག Català Cebuano Čeština Cymraeg Dansk Deutsch Diné bizaad Eesti Ελληνικά Español Esperanto Euskara فارسی Français Gaeilge Galego 한국어 Bahasa Indonesia Íslenska Italiano עברית Қазақша Kiswahili Lietuvių Magyar Nederlands 日本 語 Norsk nynorsk پنجابی Polski Русский Simple English Slovenčina Suomi Svenska தமிழ் Татарча / tatarça ไทย Українська اردو Tiếng Việt Winaray 中文 Edit links This page was last edited on 22 February 2018, at 21 : 29. 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Question: where did the hammerhead shark get its name
Answer: the unusual and distinctive structure of their heads, which are flattened and laterally extended into a "hammer" shape called a cephalofoil