Sphyrna lewiniscalloped hammerhead shark(Also: Cornuda; Mano kihikihi)

Ge­o­graphic Range

Scal­loped ham­mer­heads are pelagic sharks that are found world­wide in trop­i­cal warm water re­gions, in­clud­ing the At­lantic, In­dian, and Pa­cific oceans, be­tween 40°N to 36°S lat­ti­tude and 80°W to 80°E lon­gi­tude. ("Scal­loped Ham­mer­head Sharks, Sphyrna lewini", 1998; Car­pen­ter, 2011)

Habi­tat

Al­though they pri­mar­ily in­habit open ma­rine wa­ters, scal­loped ham­mer­heads can also be found near con­ti­nen­tal and is­land shelves and often enter bays and es­tu­ar­ies as well. ("Scal­loped Ham­mer­head Sharks, Sphyrna lewini", 1998; Car­pen­ter, 2011)

Scal­loped ham­mer­heads uti­lize dif­fer­ent habi­tats daily. At dawn, they move from their off­shore hunt­ing grounds to is­land shelves, seamounts, and en­closed bays and es­tu­ar­ies. Dur­ing the day they mi­grate to drop-off zones and reefs where fe­males form schools for the pur­pose of so­cial in­ter­ac­tion. At dusk the sharks re­turn to off­shore pelagic areas and ac­tively search for food. (Car­pen­ter, 2011; Klim­ley, et al., 1988; Klim­ley, 1987; Schlues­sel, 2008)

  • Range depth
    5 to 525 m
    16.40 to 1722.44 ft
  • Average depth
    268 m
    879.27 ft

Phys­i­cal De­scrip­tion

Scal­loped ham­mer­heads have a small but promi­nent notch in the cen­ter of their char­ac­ter­is­ti­cally-shaped head, which also bears pro­nounced grooves along its an­te­rior mar­gin, giv­ing this species its com­mon name. The side “wings” of the head are rel­a­tively nar­row and are swept back­wards. The first dor­sal fin is larger than the sec­ond and is sickle-shaped, with a rounded tip, while the sec­ond dor­sal fin has a con­cave rear edge. Both the pec­toral and dor­sal fins are slightly rounded. The tips of the pec­toral fins are ei­ther a dark grey or black. The cau­dal fin is het­e­ro­cer­cal and forked. Body col­oration in this species dis­plays typ­i­cal pelagic coun­ter­shad­ing, with a grey dor­sum and a white ven­tral sur­face. ("Scal­loped Ham­mer­head Sharks, Sphyrna lewini", 1998; Bester, 2012; Car­pen­ter, 2011)

  • Sexual Dimorphism
  • female larger
  • Range mass
    152.4 (high) kg
    335.68 (high) lb
  • Range length
    4.3 (high) m
    14.11 (high) ft

De­vel­op­ment

Fer­til­ized eggs de­velop into em­bryos that are nour­ished by a yolk-sac pla­centa at­tached to ei­ther of the fe­male's two uteruses. Scal­loped ham­mer­heads give birth to live young that are minia­ture ver­sions of their par­ents. (Bester, 2012)

In the Gulf of Cal­i­for­nia, fe­male ham­mer­heads were dis­cov­ered at a depth of 50 m, whereas males of a sim­i­lar size were caught at 25 m. It has been sug­gested that fe­males may grow more rapidly and ma­ture at a larger size than do males due to dif­fer­ences in food avail­abil­ity be­tween these habi­tats. (Klim­ley, 1987)

Re­pro­duc­tion

Mat­ing be­hav­ior in scal­loped ham­mer­heads is not fully un­der­stood, but it has been ob­served that dur­ing mat­ing sea­son, sex­u­ally ma­ture males mi­grate to deeper wa­ters in search of fe­males. Since schools are formed pri­mar­ily of fe­males, male sharks will enter and swim in an S shape, sig­nal­ing the de­sire to mate. Larger and more sex­u­ally ma­ture fe­males tend to be lo­cated in the cen­ter of the schools, push­ing smaller fe­males to the out­side. When a male lo­cates a re­cep­tive fe­male, he bites her pec­toral fin and se­cures him­self. Dur­ing mat­ing, he curls his tail around her body to align their gen­i­talia and in­serts one of his claspers (mod­i­fied anal fins) into her uro­gen­i­tal open­ing to de­posit sperm. Be­cause scal­loped ham­mer­heads are neg­a­tively buoy­ant, the mat­ing pair sinks while cop­u­la­tion oc­curs. ("Con­ven­tion on In­ter­na­tional Trade in En­dan­gered Species", 2012; Car­pen­ter, 2011; G., 2001; Kotas, et al., 2011; Stevens and Lyle, 1989)

Re­pro­duc­tive ma­tu­rity of fe­male sharks can some­times be de­ter­mined through mor­pho­log­i­cal mea­sure­ments. De­pend­ing on the lo­ca­tion of the shark (North­ern or South­ern hemi­sphere), some fe­male sharks can begin re­pro­duc­tion any­where from 15 to 17 years old, which cor­re­sponds to a total length of over 2 me­ters. Male sharks reach sex­ual ma­tu­rity at 6 years old, and around 1.5 me­ters in length. In North­ern Aus­tralia, the breed­ing sea­son oc­curs from Feb­ru­ary to March, al­though this is likely to vary ac­cord­ing to ge­o­graphic re­gion. After a ges­ta­tion pe­riod of 9 to 10 months, lit­ters of 12 to 38 young mea­sur­ing 38 to 45 cm are born live. There is no pub­lished in­for­ma­tion re­gard­ing the birth mass of pups, which is due to the fact that preg­nant fe­males are rarely caught. Im­me­di­ately after birth, pups must find their own food, but they usu­ally live in large schools until adult­hood. ("Con­ven­tion on In­ter­na­tional Trade in En­dan­gered Species", 2012; Bester, 2012; Car­pen­ter, 2011; G., 2001; Kotas, et al., 2011; Stevens and Lyle, 1989)

  • Breeding interval
    It is thought that scalloped hammerheads breed every other year.
  • Breeding season
    The breeding season for northern Australian scalloped hammerheads occurs from February to March.
  • Range number of offspring
    12 to 41
  • Range gestation period
    8 to 12 months
  • Range age at sexual or reproductive maturity (female)
    15 to 17 years
  • Range age at sexual or reproductive maturity (male)
    6 (low) years

As in other vi­vip­a­rous species, fe­male scal­loped ham­mer­heads pro­vide nu­tri­tion and pro­tec­tion to their in­ter­nally de­vel­op­ing young. As in other sharks, there is no parental care after birth. (Bester, 2012; Car­pen­ter, 2011)

Lifes­pan/Longevity

The old­est known scal­loped ham­mer­head was 31.5 years old, and was caught in the At­lantic Ocean, off the coast of Brazil. The au­thors of that study es­ti­mated the max­i­mum lifes­pan of this species to be 55 years. In a sep­a­rate study con­ducted off the coast of Sinoloa, Mex­ico, the old­est in­di­vid­ual sam­pled was ap­prox­i­mately 10.5 years old. There is no pub­lished in­for­ma­tion avail­able for the ex­pected lifes­pan of this species in cap­tiv­ity. (Anis­lado-To­lentino, et al., 2008; Kotas, et al., 2011)

  • Range lifespan
    Status: wild
    10.5 to 31.5 years
  • Typical lifespan
    Status: wild
    55 (high) years

Be­hav­ior

Both male and fe­male adults may be found alone, in pairs, or in schools. How­ever, most fe­males are found in sex­u­ally seg­re­gated schools with larger, more ma­ture fe­males in the cen­ter. Young scal­loped ham­mer­heads live in large schools until they reach ma­tu­rity. Adult males al­most ex­clu­sively enter schools when in search of a mate. (Klim­ley, 1987; Stevens and Lyle, 1989)

Home Range

Scal­loped ham­mer­heads ap­pear to reg­u­larly move through a rea­son­ably well-de­fined area as a re­sult of their diel move­ment pat­terns. How­ever, es­ti­mates for the total area en­com­passed by these move­ments are cur­rently un­avail­able. It is also thought that this species un­der­takes longer sea­sonal mi­gra­tions, so clas­si­fi­ca­tion of their daily move­ment areas as true home ranges may be in­cor­rect. (Klim­ley and Nel­son, 1984; Klim­ley, 1987)

Com­mu­ni­ca­tion and Per­cep­tion

Like all sharks, scal­loped ham­mer­heads use their eyes for vi­sual per­cep­tion, and nares for de­tec­tion of chem­i­cal cues. Like other elas­mo­branchs, they have spe­cial sen­sory or­gans called Am­pul­lae of Loren­zini; these spe­cial elec­trore­cep­tors are lo­cated on the un­der­side of the snout and "ham­mer", and aid in the de­tec­tion of buried prey, as well as nav­i­ga­tion (by sens­ing changes in the Earth's mag­netic field). Pa­cific scal­loped ham­mer­heads are able to fol­low ge­o­log­i­cal fault lines along the ocean floor. Re­cently cooled magma forms rocks that have a strong mag­netic sig­nal, which the an­i­mals fol­low to the lo­ca­tions where they form con­gre­ga­tions to feed, school, and mate. (Carter, 1967)

Sharks are able to vi­su­ally dis­play ag­gres­sion, sub­mis­sion, and dom­i­nance to con­specifics. When pro­voked or threat­ened, an in­di­vid­ual will point its pec­toral fins down­ward and arch its back. Sharks in­di­cate sub­mis­sion by rapidly shak­ing their head side to side. Dom­i­nant sharks ex­hibit a “corkscrew­ing”, or up­ward swim­ming pat­tern, and will ram sub­mis­sive sharks with their snout. (Carter, 1967)

  • Communication Channels
  • visual

Food Habits

Younger in­di­vid­u­als tend to feed in coastal wa­ters, on ben­thic and ner­itic fish. Adults live in deeper oceanic wa­ters, feed­ing on ner­itic and epipelagic fishes and cephalopods (squid, oc­to­pus and cut­tle­fishes), lob­sters, shrimps, and crabs, as well as var­i­ous smaller sharks and rays. Ham­mer­heads lo­cated in the Indo-West Pa­cific have been ob­served to prey on sea snakes. Scal­loped ham­mer­heads ac­tively for­age for food dur­ing the night, using a “smash and grab” feed­ing tech­nique. They ac­cel­er­ate to­wards prey and ei­ther swal­low it whole, or dis­able prey by bit­ing it. Great ham­mer­heads (Sphyrna mokar­ran) have been ob­served using their ham­mer-like head to pin stingrays to the ocean floor be­fore con­sum­ing them, and it is thought that scal­loped ham­mer­heads may use the same tech­nique. ("Scal­loped Ham­mer­head Sharks, Sphyrna lewini", 1998)

  • Animal Foods
  • reptiles
  • fish
  • mollusks
  • aquatic crustaceans
  • other marine invertebrates

Pre­da­tion

While scal­loped ham­mer­heads are one of the largest reef fishes and a top preda­tor, they are oc­ca­sion­ally preyed on by larger tiger sharks (Ga­le­o­cerdo cu­vier), great white sharks (Car­char­o­don car­charias), and killer whales (Or­ci­nus orca). Hu­mans also har­vest ham­mer­heads for their fins, which are sold in the lu­cra­tive global shark fin trade. (Kilm­ley, 1985)

Scal­loped ham­mer­heads form schools that con­sist mainly of fe­males, with males rarely en­ter­ing these ag­gre­ga­tions. This be­hav­ior low­ers an in­di­vid­ual’s chance of being at­tacked by preda­tors. Scal­loped ham­mer­heads also ex­hibit coun­ter­shad­ing as a form of cam­ou­flage in open water, with a grey to bronze col­ored dor­sum and a pale white/grey un­der­side. (Kilm­ley, 1985)

  • Anti-predator Adaptations
  • cryptic

Ecosys­tem Roles

Scal­loped ham­mer­heads are among the largest of reef sharks, mak­ing them top preda­tors of the an­i­mals on which they prey. (Bester, 2012)

Scal­loped ham­mer­heads have mu­tu­al­is­tic sym­bioses with sev­eral species of cleaner fish, al­low­ing wrasses and blennies to re­move ex­ter­nal par­a­sites from their skin, gills, and mouths. (Bester, 2012)

This species is a host to sev­eral types of ec­topar­a­sitic in­ver­te­brates. At least one leech and over half a dozen cope­pod species have also been found on the un­der­side of scal­loped ham­mer­head snouts. In ad­di­tion, this species plays host to at least two dif­fer­ent types of platy­helminth en­dopar­a­sites. (Bester, 2012; Bray, 1984; Cressey, 1970; Ro­kicki and By­chawska, 1991; Shields, 1985)

Mu­tu­al­ist Species
Com­men­sal/Par­a­sitic Species

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Scal­loped ham­mer­heads serve as an im­por­tant re­source for tra­di­tional fish­eries in Mex­ico. They are fished both com­mer­cially and recre­ation­ally, and highly val­ued for their fins. While their meat has a high con­cen­tra­tion of urea and is not typ­i­cally con­sumed, the skin is used for leather and oil is ob­tained from the liver. Their jaws and teeth are also sold as ma­rine cu­rios. ("Con­ven­tion on In­ter­na­tional Trade in En­dan­gered Species", 2012)

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Large ham­mer­head sharks are con­sid­ered to pose a po­ten­tial dan­ger to hu­mans. To date, how­ever, there have been no con­firmed at­tacks on hu­mans by this species. ("ISAF Sta­tis­tics on At­tack­ing Species of Shark", 2012)

  • Negative Impacts
  • injures humans
    • bites or stings

Con­ser­va­tion Sta­tus

Scal­loped ham­mer­heads are listed as an en­dan­gered species by the IUCN Red List, since they are vul­ner­a­ble to il­le­gal fish­ing and by­catch dur­ing all stages of their lives, mak­ing them sus­cep­ti­ble to ex­tinc­tion in the fu­ture. In 2007, sur­veys in the north­west At­lantic doc­u­mented a 98 per­cent de­cline from his­tor­i­cal es­ti­mates, while a 90 per­cent de­cline in pop­u­la­tion abun­dance was noted in the south­west At­lantic. ("Con­ven­tion on In­ter­na­tional Trade in En­dan­gered Species", 2012)

As of 2012, ham­mer­heads made up ap­prox­i­mately 6% of the iden­ti­fied fins en­ter­ing the Hong Kong mar­ket, trans­lat­ing to an es­ti­mated 1.3 mil­lion to 2.7 mil­lion ham­mer­heads being ex­ploited an­nu­ally for the global fin trade. This level of ex­ploita­tion is un­likely to be sus­tain­able and can have sub­stan­tial neg­a­tive im­pacts on ma­rine ecosys­tems world­wide. ("Con­ven­tion on In­ter­na­tional Trade in En­dan­gered Species", 2012)

The In­ter­na­tional Com­mis­sion for the Con­ser­va­tion of At­lantic Tunas (ICCAT) has banned the re­ten­tion of ham­mer­head sharks caught while tuna fish­ing, but this mea­sure does not ad­dress the im­pact of the lu­cra­tive shark fin trade. The U.S.A. passed the Shark Con­ser­va­tion Act of 2010 to pre­vent finning with US wa­ters. ("Con­ven­tion on In­ter­na­tional Trade in En­dan­gered Species", 2012)

Con­trib­u­tors

Erick Ruiz (au­thor), San Diego Mesa Col­lege, Sierra Tru­jillo (au­thor), San Diego Mesa Col­lege, Paul De­twiler (ed­i­tor), San Diego Mesa Col­lege, Je­remy Wright (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cosmopolitan

having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

electric

uses electric signals to communicate

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

magnetic

(as perception channel keyword). This animal has a special ability to detect the Earth's magnetic fields.

migratory

makes seasonal movements between breeding and wintering grounds

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

piscivore

an animal that mainly eats fish

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

Ref­er­ences

2012. "Con­ven­tion on In­ter­na­tional Trade in En­dan­gered Species" (On-line). Cites.​org. Ac­cessed May 07, 2012 at http://​www.​cites.​org/​common/​com/​AC/​26/​E26-01i.​pdf.

2010. "Fif­teenth Meet­ing of the Con­fer­ence of the Par­ties" (On-line pdf). www.​Cites.​org. Ac­cessed May 07, 2012 at <http://​www.​cites.​org/​eng/​cop/​15/​prop/​E-15-prop-15.​pdf>..

In­ter­na­tional Shark At­tack File, Florida Mu­seum of Nat­ural His­tory, Uni­ver­sity of Florida. 2012. "ISAF Sta­tis­tics on At­tack­ing Species of Shark" (On-line). In­ter­na­tional Shark At­tack File. Ac­cessed July 11, 2012 at http://​www.​flmnh.​ufl.​edu/​fish/​sharks/​statistics/​species2.​htm.

1998. "Scal­loped Ham­mer­head Sharks, Sphyrna lewini" (On-line). Marinebio.​org. Ac­cessed May 07, 2012 at http://​marinebio.​org/​species.​asp?​id=86.

Anis­lado-To­lentino, V., M. Ca­bello, F. Linares, C. Men­doza. 2008. Age and growth of the scal­loped ham­mer­head shark, Sphyrna lewini (Grif­fith & Smith, 1834) from the South­ern coast of Sinoloa, México. Hidro­biológica, 18: 31-40.

Baum, J., S. Clarke, A. Domingo, M. Ducrocq, et.​al. 2011. "Sphyrna lewini En­dan­gered" (On-line). redlist.​org. Ac­cessed May 07, 2012 at http://​www.​iucnredlist.​org/​apps/​redlist/​details/​39385/​0.

Bester, C. 2012. "Great Ham­mer­head" (On-line). Florida Mu­seum of Nat­ural His­tory. Ac­cessed May 07, 2012 at <http://​www.​flmnh.​ufl.​edu/​fish/​gallery/​descript/​greathammerhead/​ghammerhead.​html>. .

Bray, R. 1984. Some helminth par­a­sites of ma­rine fishes and cephalopods of South Africa: As­pi­do­gas­trea and the di­ge­nean fam­i­lies Bu­cephal­i­dae, Hap­los­planch­nidae, Me­sometri­dae and Fel­lodis­to­mi­dae. Jour­nal of Nat­ural His­tory, 18/2: 271-292.

Car­pen­ter, K. 2011. "Sphyrna lewini, Scal­loped ham­mer­head" (On-line). Fishbase.​us. Ac­cessed May 07, 2012 at <http://​www.​fishbase.​us/​summary/​Sphyrna-lewini.​html>. .

Carter, G. 1967. A re­vi­sion of the ham­mer­head sharks (Fam­ily Sphrynida). Pro­ceed­ings of the United States Na­tional Mu­seum: Smith­son­ian In­sti­tu­tion, 119/3539: 1-98.

Cressey, R. 1970. Cope­pods par­a­sitic on sharks from the west coast of Florida. Smith­son­ian Con­tri­bu­tions to Zo­ol­ogy, 38: 1-30.

G., J. 2001. "Scal­loped Ham­mer­head Shark" (On-line). Shedd-The Worlds Aquar­ium. Ac­cessed May 07, 2012 at http://​sea.​sheddaquarium.​org/​sea/​fact_​sheets.​asp?​id=67.

Hazin, F., A. Fis­cher, M. Broad­hurst. 2001. "As­pects of re­pro­duc­tive bi­ol­ogy of the scal­loped ham­mer­head shark, Sphyrna lewini, off north­east­ern Brazil". En­vi­ron­men­tal Bi­ol­ogy of Fishes, 61: 151-159. Ac­cessed May 07, 2012 at <http://​sharkmans-world.​eu/​research/​sphyrna.​pdf>. .

Kilm­ley, A. 1985. "School­ing in Sphyrna lewini, a species with low risk of pre­da­tion: A non-egal­i­tar­ian state". In­ter­na­tional Jour­nal of Be­hav­ioural Bi­ol­ogy, 70/4: 297-319.

Klim­ley, A., S. But­ler, D. Nel­son, A. Stull. 1988. "Diel move­ments of scal­loped ham­mer­head sharks, Sphyrna lewini Grif­fith and Smith, to and from a seamount in the Gulf of Cal­i­for­nia". Jour­nal of Fish Bi­ol­ogy, 33/5: 751-761.

Klim­ley, A., D. Nel­son. 1984. Diel move­ment pat­terns of the scal­loped ham­mer­head shark (Sphyrna lewim) in re­la­tion to E1 Bajo Es­pir­itu Santo: a refug­ing cen­tral-po­si­tion so­cial sys­tem. Be­hav­ioral Ecol­ogy and So­cio­bi­ol­ogy, 15: 45-54.

Klim­ley, A. 1987. "The de­ter­mi­nants of sex­ual seg­re­ga­tion in the Scal­loped Ham­mer­head shark, Sphyrna lewini". En­vi­ron­men­tal Bi­ol­ogy of Fishes, 18/1: 27-40. Ac­cessed May 07, 2012 at http://​home.​eckerd.​edu/​~mey­lanpa/Bi­ol­o­gy­Sem­i­nar/pdf­s_of_­pa­per­s_­to_read/BenC_Binder1.pdf.

Kotas, J., V. Mas­trochirico, M. Pe­trere. 2011. "Age and growth of the Scal­loped Ham­mer­head shark, Sphyrna lewini (Grif­fith and Smith, 1834), from the south­ern Brazil­ian coast/Idade e cresci­mento do tubarão-martelo-en­tal­hado, Sphyrna lewini (Grif­fith and Smith, 1834), da costa sul do Brasil". Brazil­ian Jour­nal of Bi­ol­ogy, 71/3: 755-761.

Ro­kicki, J., D. By­chawska. 1991. Par­a­sitic cope­pods of Car­charhinidae and Sphyri­dae (Elas­mo­branchia) from the At­lantic Ocean. Jour­nal of Nat­ural His­tory, 25/6: 1439-1448.

Schlues­sel, V. 2008. "Mor­pho­me­t­ric and ul­tra­struc­tural com­par­i­son of the ol­fac­tory sys­tem in elas­mo­branchs: The sig­nif­i­cance of struc­ture–func­tion re­la­tion­ships based on phy­logeny and ecol­ogy". Jour­nal of Mor­phol­ogy, 269/11: 1365-1386.

Shields, J. 1985. Sur­face mor­phol­ogy and de­scrip­tion of Oto­both­rium kurisi new species (Ces­toda: Try­panorhyn­cha) from a ham­mer­head shark, Sphyrna lewini. In­ter­na­tional Jour­nal for Par­a­sitol­ogy, 15/6: 635-643.

Stevens, J., J. Lyle. 1989. "Bi­ol­ogy of three ham­mer­head sharks (Eu­sphyra blochii, Sphyrna mokar­ran and Sphyrna lewini) from North­ern Aus­tralia". Aus­tralian Jour­nal of Ma­rine and Fresh­wa­ter Re­search, 40/2: 129-146.