Hammerhead shark

Hammerhead Sharks can vary in length and weight. The largest species of Hammerhead Sharks, the Great Hammerhead, has an average length of 13.1 feet and weight of 500 pounds.{{Cite web |title=Great Hammerhead Shark |url=https://oceana.org/marine-life/great-hammerhead-shark/ |access-date=2025-04-24 |website=Oceana |language=en-US}} While the smallest species of Hammerhead, the Bonnethead Shark, can reach 5 feet in length and 24 pounds in weight.{{Cite web |last=Fisheries |first=NOAA |date=2025-04-14 |title=Bonnethead Shark {{!}} NOAA Fisheries |url=https://www.fisheries.noaa.gov/species/bonnethead-shark |access-date=2025-04-24 |website=NOAA |language=en}} One specimen caught off the Florida coast in 1906 weighed over {{convert|680|kg|lb|abbr=on}}.{{cite web|url= https://chroniclingamerica.loc.gov/lccn/sn83030214/1906-04-15/ed-1/seq-18/print/image_681x581_from_1924%2C0_to_4549%2C2240/|title= Hammerhead Shark Captured in Florida Waters|author= New-York Tribune|date= 15 April 1906|website= Chronicling America|publisher= New-York Tribune|access-date= 20 September 2022|archive-date= 20 September 2022|archive-url= https://web.archive.org/web/20220920201252/https://chroniclingamerica.loc.gov/lccn/sn83030214/1906-04-15/ed-1/seq-18/print/image_681x581_from_1924,0_to_4549,2240/|url-status= live}} They are usually light gray and have a greenish tint. Their bellies are white, which allows them to blend into the background when viewed from below and sneak up to their prey.{{cite web| url= http://www.sharks-world.com/hammerhead_shark.html| title= Hammerhead Shark| website= sharks-world.com| date= | publisher= | access-date= 19 December 2012| archive-date= 7 July 2011| archive-url= https://web.archive.org/web/20110707050317/http://www.sharks-world.com/hammerhead_shark.html| url-status= dead}} Their heads have lateral projections that give them a hammer-like shape. While overall similar, this shape differs somewhat between species; examples are: a distinct T-shape in the great hammerhead, a rounded head with a central notch in the scalloped hammerhead, and an unnotched rounded head in the smooth hammerhead.{{Cite web|title=Marine Species ID: Great Hammerhead vs. Scalloped and Smooth Hammerhead|url=https://www.sportdiver.com/marine-species-id-great-hammerhead-vs-scalloped-and-smooth-hammerhead|access-date=7 October 2020|website=Sport Diver|language=en|archive-date=8 August 2021|archive-url=https://web.archive.org/web/20210808031143/https://www.sportdiver.com/marine-species-id-great-hammerhead-vs-scalloped-and-smooth-hammerhead|url-status=live}}

Hammerheads have disproportionately small mouths compared to other shark species. Some species are also known to form schools.{{Cite web |title=Hammerhead shark {{!}} Diet, Size, & Facts {{!}} Britannica |url=https://www.britannica.com/animal/hammerhead-shark |access-date=26 July 2023 |website=www.britannica.com |language=en |archive-date=24 July 2023 |archive-url=https://web.archive.org/web/20230724051000/https://www.britannica.com/animal/hammerhead-shark |url-status=live }} In the evening, like most other sharks, they become solitary hunters.{{Cite web |last=Ward-Sing |first=Elizabeth |date=2017-05-12 |title=Great Hammerhead Shark |url=https://www.sharkguardian.org/post/great-hammerhead-shark |access-date=2025-03-04 |website=Shark Guardian |language=en}} National Geographic explained that hammerheads can be found in warm, tropical waters, but during the summer, they begin a mass migration period in search of colder waters.{{cite web| url= http://animals.nationalgeographic.com/animals/fish/hammerhead-shark/| title= Hammerhead Shark| website= NationalGeographic.com| access-date= 9 November 2016| date= 10 September 2010| archive-date= 10 November 2016| archive-url= https://web.archive.org/web/20161110101800/http://animals.nationalgeographic.com/animals/fish/hammerhead-shark/| url-status= dead}}

File:Hammerhead Shark - Marko Dimitrijevic.jpg

Since sharks do not have mineralized bones and rarely fossilize, only their teeth are commonly found as fossils. Their closest relatives are the requiem sharks (Carcharinidae). Based on DNA studies and fossils, the ancestor of the hammerheads probably lived in the Early Miocene epoch about 20 million years ago.{{cite news| url= https://www.sciencedaily.com/releases/2010/05/100518113132.htm| title= Hammerhead shark study shows cascade of evolution affected size, head shape| date= 19 May 2010| website= ScienceDaily.com| publisher= University of Colorado at Boulder| access-date= 9 November 2016| archive-date= 1 April 2019| archive-url= https://web.archive.org/web/20190401175733/https://www.sciencedaily.com/releases/2010/05/100518113132.htm| url-status= live}}{{cite journal |last1=Mello |first1=Waldiney |last2=Brito |first2=Paulo Marques Machado |title=Contributions to the tooth morphology in early embryos of three species of hammerhead sharks (Elasmobranchii: Sphyrnidae) and their evolutionary implications |journal=Comptes Rendus. Biologies |date=September 2013 |volume=336 |issue=9 |pages=466–471 |doi=10.1016/j.crvi.2013.04.017 |pmid=24161244 |url=https://comptes-rendus.academie-sciences.fr/biologies/articles/10.1016/j.crvi.2013.04.017/ }}

Using mitochondrial DNA, a phylogenetic tree of the hammerhead sharks showed the winghead shark as sister to the rest of the hammerhead sharks. 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.{{cite web| first= R. Aidan| last= Martin| title= Origin and Evolution of the 'Hammer'| website= elasmo-research.org| url= http://www.elasmo-research.org/education/topics/d_hh_origin.htm| access-date= 31 January 2005| archive-date= 27 December 2018| archive-url= https://web.archive.org/web/20181227052545/http://www.elasmo-research.org/education/topics/d_hh_origin.htm| url-status= live}}

The hammer-like shape of the head may have evolved at least in part to enhance the animal's vision.{{cite journal|doi=10.1242/jeb.032615 |title=Enhanced visual fields in hammerhead sharks |journal= Journal of Experimental Biology|volume=212|issue=24|pages=4010–8|year=2009|last1=McComb|first1=D. M. |last2= Tricas| first2= T. C.| last3= Kajiura| first3= S. M. | pmid=19946079|doi-access=free|bibcode=2009JExpB.212.4010M }} The positioning of the eyes, mounted on the sides of the shark's distinctive hammer head, allows 360° of vision in the vertical plane, meaning the animals can see above and below them at all times.{{cite news | first=D. Michelle | last=McComb | url=http://news.bbc.co.uk/earth/hi/earth_news/newsid_8376000/8376740.stm | work=BBC News | title=Hammerhead shark mystery solved | date=27 November 2009 | access-date=4 May 2010 | display-authors=etal | archive-date=25 February 2010 | archive-url=https://web.archive.org/web/20100225034122/http://news.bbc.co.uk/earth/hi/earth_news/newsid_8376000/8376740.stm | url-status=live }}{{Cite web|title = World's Deadliest: Hammerhead Sharks|url = http://video.nationalgeographic.com/video/worlds-deadliest/deadliest-hammerhead-shark|website = video.nationalgeographic.com|access-date = 23 May 2015|archive-date = 23 April 2015|archive-url = https://web.archive.org/web/20150423144008/http://video.nationalgeographic.com/video/worlds-deadliest/deadliest-hammerhead-shark|url-status = dead}} They also have an increased binocular vision and depth of visual field as a result of the cephalofoil.{{cite web | last=Barley | first=Shanta | title=Why the hammerhead shark got its hammer | website=New Scientist | date=26 February 2019 | url=https://www.newscientist.com/article/dn18210-why-the-hammerhead-shark-got-its-hammer/ | access-date=3 March 2021 | archive-date=3 March 2021 | archive-url=https://web.archive.org/web/20210303061234/https://www.newscientist.com/article/dn18210-why-the-hammerhead-shark-got-its-hammer/ | url-status=live }}{{Cite web |title=Great Hammerhead Shark - Lifestyle, Diet, and More - Wildlife Explained |last=Explained |first=Wildlife |work=Wildlife Explained |date= 5 January 2022|access-date=10 August 2023 |url= https://www.wildlifeexplained.com/great-hammerhead-shark/}} 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. The unusual structure of its vertebrae, though, has been found to be 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 hammerhead 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 electric fields generated by other living creatures.{{cite book|last1=Otfinoski|first1=Steven|title=Hammerheads and Other Sharks|date=2000|publisher=World Book, Inc.|isbn=978-0716612100|pages=[https://archive.org/details/hammerheadsother0000otfi_y3q2/page/16 16]|url=https://archive.org/details/hammerheadsother0000otfi_y3q2/page/16}} By distributing the receptors over a wider area, like a larger radio antenna, hammerheads can sweep for prey more effectively.{{cite web | first=R. Aidan | last=Martin | title=If I Had a Hammer | work=Rodale's Scuba Diving | date=August 1993 | url=http://www.elasmo-research.org/education/topics/d_functions_of_hammer.htm |publisher=ReefQuest Centre for Shark Research | access-date=31 March 2006 | archive-date=18 February 2019 | archive-url=https://web.archive.org/web/20190218042914/http://www.elasmo-research.org/education/topics/d_functions_of_hammer.htm | url-status=live }}

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.{{cite web|url=http://www.aquaticcommunity.com/sharkfish/hammerheadshark.php |title=Hammerhead Shark |archive-url=https://web.archive.org/web/20190130105212/http://www.aquaticcommunity.com/sharkfish/hammerheadshark.php |archive-date=30 January 2019 |website=Aquatic Community |access-date=19 December 2012 |url-status=live}} 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 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.{{cite journal |last1=Chapman |first1=DD |last2=Shivji |first2=MS |last3=Louis |first3=E |last4=Sommer |first4=J |last5=Fletcher |first5=H |last6=Prodöhl |first6=PA |title=Virgin birth in a hammerhead shark |volume=3 |issue=4 |date=22 August 2007 |journal=Biology Letters |doi=10.1098/rsbl.2007.0189 |pmc=2390672 |doi-access=free |pmid=17519185 |pages=425–7}}

Hammerhead sharks eat a large range of prey such as fish (including other sharks), squid, octopus, and crustaceans. Stingrays are a particular favorite, with the positioning of their (comparatively) smaller, crescent-shaped mouths underneath their T-shaped heads allowing for skilled skate, ray, and flounder hunting, among other seafloor-dwellers. These sharks will often be found swimming above the sand along the bottom of the ocean, stalking their prey. Their unique heads are further utilized as a tool (or weapon) if hunting rays and flatfishes; the shark uses its head to pin down and briefly stun the prey, and only eats once their quarry is clearly weakened and in shock. The great hammerhead, tending to be larger and more aggressive to its own kind than other hammerheads, occasionally engages in cannibalism, eating other hammerhead sharks, including mothers consuming their own young.{{cite web| url= http://www.enchantedlearning.com/subjects/sharks/species/Hammerhead.shtml| title= Great hammerhead shark| publisher= Enchanted Learning | access-date= 19 December 2012| archive-date= 30 December 2018| archive-url= https://web.archive.org/web/20181230230713/https://www.enchantedlearning.com/subjects/sharks/species/Hammerhead.shtml| url-status= live}} In addition to the typical animal prey, bonnetheads have been found to feed on seagrass, which sometimes makes up as much as half their stomach contents. They may swallow it unintentionally, but they are able to partially digest it. At the time of discovery, this was the only known case of a potentially omnivorous species of shark{{cite web|url=http://news.nationalgeographic.com/2017/06/bonnethead-sharks-eat-seagrass/|title=This Shark Eats Grass, and No One Knows Why|date=29 June 2017|author=Hannah Lang|website=National Geographic|access-date=7 December 2018|archive-date=23 April 2019|archive-url=https://web.archive.org/web/20190423105833/https://news.nationalgeographic.com/2017/06/bonnethead-sharks-eat-seagrass/|url-status=dead}} (since then, whale sharks were also found to be omnivorous).{{Cite journal |last1=Meekan |first1=M. G. |last2=Virtue |first2=P. |last3=Marcus |first3=L. |last4=Clements |first4=K. D. |last5=Nichols |first5=P. D. |last6=Revill |first6=A. T. |date=2022 |title=The world's largest omnivore is a fish |journal=Ecology |volume=103 |issue=12 |pages=e3818 |doi=10.1002/ecy.3818 |pmid=35852891 |doi-access=free |bibcode=2022Ecol..103E3818M }}

There are ten distinct species of Hammerhead sharks in the wild:{{Cite journal |last=Chin |first=A. |last2=Simpfendorfer |first2=C. A. |last3=White |first3=W. T. |last4=Johnson |first4=G. J. |last5=McAuley |first5=R. B. |last6=Heupel |first6=M. R. |date=2017-04-21 |title=Crossing lines: a multidisciplinary framework for assessing connectivity of hammerhead sharks across jurisdictional boundaries |url=https://www.nature.com/articles/srep46061 |journal=Scientific Reports |language=en |volume=7 |issue=1 |pages=46061 |doi=10.1038/srep46061 |issn=2045-2322|pmc=5399444 }}

File:Hammerhead Atlantis.jpg

According to the International Shark Attack File, humans have been subjects of 17 documented, unprovoked attacks by hammerhead sharks within the genus Sphyrna since AD 1580. No human fatalities have been recorded.{{Cite web |url=https://www.floridamuseum.ufl.edu/fish/isaf/contributing-factors/species-implicated-attacks/ |title=Statistics on Attacking Species of Shark |website=Florida Museum of Natural History |access-date=27 December 2017 |archive-date=15 December 2017 |archive-url=https://web.archive.org/web/20171215085814/https://www.floridamuseum.ufl.edu/fish/isaf/contributing-factors/species-implicated-attacks |url-status=live }} Most hammerhead shark species are too small to inflict serious damage to humans.

File:A man carries a huge hammerhead through the streets of Mogadishu (edit).jpg shark along a street in Mogadishu, Somalia]]

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. The young swim mostly in shallow waters along shores all over the world to avoid predators.{{cite journal |last1=Royer |first1=Mark |last2=Meyer |first2=Carl |last3=Royer |first3=John |last4=Maloney |first4=Kelsey |last5=Cardona |first5=Edward |last6=Blandino |first6=Chloé |last7=Fernandes da Silva |first7=Guilherme |last8=Whittingham |first8=Kate |last9=Holland |first9=Kim N. |title='Breath holding' as a thermoregulation strategy in the deep-diving scalloped hammerhead shark |journal=Science |date=12 May 2023 |volume=380 |issue=6645 |pages=651–655 |doi=10.1126/science.add4445 |pmid=37167384 |bibcode=2023Sci...380..651R }}

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.{{cite news | url= https://www.washingtonpost.com/wp-dyn/content/article/2011/02/25/AR2011022505123.html | title= Panamanian officials find half ton of shark fins | agency= Associated Press | website= WashingtonPost.com | date= 25 February 2011 | access-date= 7 December 2018 | archive-date= 12 June 2018 | archive-url= https://web.archive.org/web/20180612163155/http://www.washingtonpost.com/wp-dyn/content/article/2011/02/25/AR2011022505123.html | url-status= live }} This practice, known as finning, is lethal to the shark.{{cite news |url = http://www.iwmc.org/PDF/StraitsTPress.pdf |author = Giam Choo Hoo |title = Shark's fin soup – eat without guilt |date = 1 December 2006 |newspaper = The Straits Times |access-date = 6 January 2007 |url-status = dead |archive-url = https://web.archive.org/web/20070221165724/http://www.iwmc.org/PDF/StraitsTPress.pdf |archive-date = 21 February 2007}}

File:Scalloped hammerhead-tokyosealifepark-2019-1-8.webm swimming]]

The relatively small bonnethead is regular at public aquariums, as it has proven easier to keep in captivity than the larger hammerhead species,{{cite book |author=Compagno, L. |author2=M. Dando |author3=S. Fowler |name-list-style=amp |year=2004 |title=Sharks of the World |page=325 |publisher=HarperCollins | isbn=978-0-00-713610-0}}{{Cite book|title =Elasmobranch Husbandry Manual: Captive Care of Sharks, Rays, and their Relatives |editor1= Smith, M. |editor2=D. Warmolts |editor3=D. Thoney |editor4=R. Hueter | year=2004 | publisher=Ohio Biological Survey | isbn=978-0-86727-152-2 }}{{pn|date=March 2025}} and it has been bred at a handful of facilities.{{Cite web|title = Babies Of The S.E.A. – Bonnethead Shark| work=S.E.A. Aquarium at Resorts World Sentosa |url = http://seaa.rwsentosablog.com/bonnethead-shark/|publisher = SEA Aquarium|access-date = 13 September 2017|date = November 2013|archive-date = 14 September 2017|archive-url = https://web.archive.org/web/20170914124943/http://seaa.rwsentosablog.com/bonnethead-shark/|url-status = live}} Nevertheless, at up to {{convert|1.5|m|ft|abbr=on|0}} in length and with highly specialized requirements, very few private aquarists have the experience and resources necessary to maintain a bonnethead in captivity.{{Cite web |title =The Bonnethead Shark Sphyrna tiburo: Is it Suitable for Home Aquariums? |url =http://www.tfhmagazine.com/details/articles/the-bonnethead-shark-sphyrna-tiburo-is-it-suitable-for-home-aquariums.htm |publisher =TFH Magazine |date =September 2007 |access-date =13 September 2017 |archive-date =14 September 2017 |archive-url =https://web.archive.org/web/20170914035512/http://www.tfhmagazine.com/details/articles/the-bonnethead-shark-sphyrna-tiburo-is-it-suitable-for-home-aquariums.htm |url-status =live }} 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 heads, so they require very large, specially adapted tanks.{{Cite journal | title=Husbandry of scalloped hammerhead sharks Sphyrna lewini (Griffith & Smith, 1834) at Reef HQ Aquarium, Townsville, Australia | url=http://www.reefhq.com.au/__data/assets/pdf_file/0005/234356/Husbandry-of-Hammerhead-Sharks_Tristram-et-al_2014.pdf | author1=Tristram, H. | author2=S. Thomas | author3=L. Squire-Junior | year=2014 | journal=Der Zoologische Garten | volume=83 | issue=4–6 | pages=93–113 | doi=10.1016/j.zoolgart.2014.08.002 | bibcode=2014DZGar..83...93T | access-date=7 December 2018 | archive-date=7 August 2020 | archive-url=https://web.archive.org/web/20200807235551/https://www.reefhq.com.au/__data/assets/pdf_file/0005/234356/Husbandry-of-Hammerhead-Sharks_Tristram-et-al_2014.pdf | url-status=live }} As a consequence, relatively few public aquaria 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 aquaria in most continents, but primarily in North America, Europe, and Asia.{{Cite web|title = Scalloped Hammerhead, Sphyrna lewini (Griffith & Smith)|url = http://elasmollet.org/Sl/Sl_captive.html|website = elasmollet.org|access-date = 13 September 2017|archive-date = 27 June 2015|archive-url = https://web.archive.org/web/20150627182436/http://elasmollet.org/Sl/Sl_captive.html|url-status = usurped}}{{Cite web |title =Scalloped hammerhead shark |url =http://www.zootierliste.de/en/?klasse=5&ordnung=507&familie=50708&art=50903596 |website =Zootierliste |access-date =13 September 2017 |archive-date =14 September 2017 |archive-url =https://web.archive.org/web/20170914035650/http://www.zootierliste.de/en/?klasse=5&ordnung=507&familie=50708&art=50903596 |url-status =live }} In 2014, fewer than 15 public aquaria 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).{{Cite web|title = Great Hammerheads, Sphyrna mokarran (Rueppell, 1837) in Captivity|url = http://elasmollet.org/Sm/Sm_captive.html|website = elasmollet.org|access-date = 17 December 2015|archive-date = 22 December 2015|archive-url = https://web.archive.org/web/20151222104540/http://elasmollet.org/Sm/Sm_captive.html|url-status = usurped}} Smooth hammerheads have also been kept in the past.

File:Hammerhead shark, Cocos Island, Costa Rica.jpg

Humans are the main threat to hammerhead sharks. Although they are not usually the primary target, hammerhead sharks are caught in fisheries all over the world.{{Cite report|last1=Miller|first1=Margaret H.|last2=Carlson|first2=J.|last3=Hogan|first3=L.|last4=Kobayashi|first4=D.|date=2014|title=Status review report : great hammerhead shark (Sphyrna mokarran)|url=https://repository.library.noaa.gov/view/noaa/16286|publisher=National Marine Fisheries Service, Office of Protected Resources|language=en|access-date=25 June 2023|via=National Oceanic and Atmospheric Administration|archive-date=5 February 2023|archive-url=https://web.archive.org/web/20230205163849/https://repository.library.noaa.gov/view/noaa/16286|url-status=live}} Tropical fisheries are the most common place for hammerheads to be caught because of their preference to reside in warm waters. The total number of hammerheads caught in fisheries is recorded in the Food and Agriculture Organization of the United Nations Global Capture Production dataset. The number steadily increased from 75 metric tons in 1990, to 6,313 metric tons by 2010.

Shark fin traders say that hammerheads have some of the best quality fin needles which makes them good to eat when prepared properly. Hong Kong is the world's largest fin trade market and accounts for about 1.5% of the total annual amount of fins traded. It is estimated that around 375,000 great hammerhead sharks alone are traded per year which is equivalent to 21,000 metric tons of biomass. However, most sharks that are caught are only used for their fins and then discarded. The meat of hammerheads is generally unwanted. Consumption of hammerhead meat has been recorded in Trinidad and Tobago, Venezuela, Kenya and Japan. Hammerhead sharks are particularly vulnerable to overfishing due to their tendency to form large aggregations, making them easy targets for commercial fishing operations. Recent genetic studies indicate that population fragmentation may further threaten their long-term survival, as isolated populations show reduced genetic diversity.Ovenden, J. R., Kashiwagi, T., Broderick, D., Giles, J., & Salini, J. (2005). The extent of population genetic subdivision differs among four codistributed shark species in the Indo‐Australian archipelago. Conservation Genetics, 6(2), 213–225. doi:10.1007/s10592-005-9036-2

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.{{cite web |url=https://www.bbc.co.uk/news/science-environment-21741648 |title='Historic' day for shark protection |last=McGrath |first=Matt |website=BBC News |date=11 March 2013 |access-date=27 July 2013 |archive-date=10 June 2013 |archive-url=https://web.archive.org/web/20130610193508/http://www.bbc.co.uk/news/science-environment-21741648 |url-status=live }}

Among Torres Strait Islanders, the hammerhead shark, known as the beizam, is a common family totem and often represented in cultural artefacts such as the elaborate headdresses worn for ceremonial dances, known as dhari (dari). They are associated with law and order.{{Cite web|last=Gerhardt|first=Katrin|date=30 November 2018|title=Indigenous knowledge and cultural values of hammerhead sharks in Northern Australia|url=https://www.nespmarine.edu.au/system/files/Gerhardt_Heupel%20Indigenous%20knowledge%20and%20cultural%20values%20of%20hammerhead%20sharks%20Milestone%2014%20report%20RPv4%202018.pdf|access-date=14 November 2020|website=Marine Diversity Hub|archive-date=16 November 2020|archive-url=https://web.archive.org/web/20201116030630/https://www.nespmarine.edu.au/system/files/Gerhardt_Heupel%20Indigenous%20knowledge%20and%20cultural%20values%20of%20hammerhead%20sharks%20Milestone%2014%20report%20RPv4%202018.pdf|url-status=live}} Renowned artist Ken Thaiday Snr is known for his representations of beizam in his sculptural dari and other works.{{cite web | title=Dr Ken Thaiday Senior | website=Australia Council | date=15 May 2019 | url=https://www.australiacouncil.gov.au/arts-in-daily-life/artist-stories/dr-ken-thaiday-senior/ | access-date=14 April 2020 | archive-date=12 April 2020 | archive-url=https://web.archive.org/web/20200412191727/https://www.australiacouncil.gov.au/arts-in-daily-life/artist-stories/dr-ken-thaiday-senior/ | url-status=live }}{{cite web | title=Ken Thaiday | website=Art Gallery NSW | url=https://www.artgallery.nsw.gov.au/collection/artists/thaiday-ken/ | access-date=15 April 2020 | archive-date=1 August 2020 | archive-url=https://web.archive.org/web/20200801150842/https://www.artgallery.nsw.gov.au/collection/artists/thaiday-ken/ | url-status=live }}

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, but others 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 their swimming by is a sign that the gods are watching over the families, and the oceans are clean and balanced.{{cite web|url=https://www.moolelo.com/shark-respected.html |title=Shark highly respected in Hawaiian culture |author=Hurley, Timothy |newspaper=The Honolulu Advertiser |archive-url=https://web.archive.org/web/20150905155936/http://www.moolelo.com/shark-respected.html |archive-date=5 September 2015 |via=Moolelo.com |date=28 September 2004 |access-date=19 December 2012 |url-status=live}}

{{Outline|Outline of sharks}}

{{Portal|Sharks}}

• List of hammerhead sharks
• List of prehistoric cartilaginous fish

{{Reflist|30em}}

{{Commons category|Sphyrnidae}}

• {{FishBase family | family = Sphyrnidae| month = February | year = 2011}}
• [http://animaldiversity.ummz.umich.edu/site/accounts/classification/Sphyrna.html#Sphyrna Animal Diversity Web Genus Sphyrna] with species sub-pages
• [http://jeb.biologists.org/cgi/content/full/205/23/3609 "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.
• [http://marinebio.org/species.asp?id=87 Great hammerhead shark, Sphyrna mokarran], MarineBio.org
• {{cite news| url= http://news.bbc.co.uk/2/hi/science/nature/5065510.stm |publisher=BBC News | title= New shark discovered in US waters| date=10 June 2006| access-date= 9 November 2016}}
• [https://www.marineconservation.org.au/hammerhead-sharks/ Hammerhead Sharks], Australian Marine Conservation Society
• [http://www.check123.com/videos/1037-hammerhead-shark Hammerhead Shark - Video] {{Webarchive|url=https://web.archive.org/web/20221001075645/http://www.check123.com/videos/1037-hammerhead-shark |date=1 October 2022 }} on Check123 - Video Encyclopedia

{{Carcharhiniformes}}

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Category:Extant Miocene first appearances

Category:Species that are or were threatened by use as food

Category:Taxa named by Theodore Gill

Category:Vertebrate parthenogenesis