Smalleye hammerhead

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Smalleye hammerhead
Sphyrna tudes2.jpg
CITES Appendix II (CITES) [2]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Carcharhiniformes
Family: Sphyrnidae
Genus: Sphyrna
Species:
S. tudes
Binomial name
Sphyrna tudes
(Valenciennes, 1822)
Sphyrna tudes distribution map.svg
Range of the smalleye hammerhead [3]
Synonyms

Sphyrna bigelowiS. Springer, 1944

The smalleye hammerhead (Sphyrna tudes), also called the golden hammerhead or curry shark, is a small species of hammerhead shark in the family Sphyrnidae. This species was historically common in the shallow coastal waters of the western Atlantic Ocean, from Venezuela to Uruguay. It favors muddy habitats with poor visibility, reflected by its relatively small eyes. Adult males and juveniles are schooling and generally found apart from the solitary adult females. Typically reaching 1.2–1.3 m (3.9–4.3 ft) in length, this shark has a unique, bright golden color on its head, sides, and fins, which was only scientifically documented in the 1980s. As in all hammerheads, its head is flattened and laterally expanded into a hammer-shaped structure called the cephalofoil, which in this species is wide and long with an arched front margin bearing central and lateral indentations.

Contents

The yellow-orange pigments of the smalleye hammerhead seem to have been acquired from the penaeid shrimp Xiphopenaeus kroyeri , the main food of juvenile sharks, and from sea catfish and their eggs, the main food of adults. The golden color may serve to conceal it from predators such as larger sharks. This species is viviparous, with the developing embryos sustained by a placental connection formed from the depleted yolk sac. Females bear litters of five to 19 pups every year following a gestation period of 10 months. Reproductive seasonality, litter size, and size at maturity vary between geographical regions. Because of its abundance, the smalleye hammerhead is an economically important bycatch of artisanal gillnet fisheries throughout its range, and is used as food. In recent years, overfishing has caused marked declines in its numbers off Trinidad, northern Brazil, and probably elsewhere. Coupled with the smalleye hammerhead's low reproductive rate, this led the International Union for Conservation of Nature to list the smalleye hammerhead as critically endangered in 2020.

Taxonomy and phylogeny

Despite being one of the most easily recognizable sharks, the smalleye hammerhead has had a long history of taxonomic confusion that still remains to be fully resolved. [4] Its scientific name originated in 1822, with French zoologist Achille Valenciennes' description of Zygaena tudes in the scientific journal Mémoires du Muséum National d'Histoire Naturelle; the specific epithet tudes is Latin for "hammer". Valenciennes made reference to three specimens, one from Nice in France, one from Cayenne in French Guiana, and one from the Coromandel Coast of India. [5] For over two centuries, though, taxonomists believed Valenciennes' account matched the great hammerhead, which thus became known as Zygaena (later Sphyrna) tudes. [3] The smalleye hammerhead was known by a different name, Sphyrna bigelowi, coined by Stewart Springer in a 1944 issue of Journal of the Washington Academy of Sciences. [6]

In 1950, Enrico Tortonese examined the Nice and Cayenne specimens of S. tudes (the Coromandel specimen having been lost in the interim), and concluded that they were not great hammerheads, but rather the same species as S. bigelowi. [7] Carter Gilbert concurred in his 1967 revision of the hammerhead sharks, noting that while the lost Coromandel specimen was probably a great hammerhead, none of the existing material belonged to that species. Thus, Sphyrna tudes became the accepted name for the smalleye hammerhead, taking precedence over S. bigelowi because it was published earlier, and the great hammerhead received the next available name Sphyrna mokarran. Gilbert designated the Nice specimen as the lectotype that would define S. tudes, having priority over the Cayenne specimen (the paralectotype). This was meant to stabilize the name, but had the opposite effect. [3] [8]

In 1981, Jean Cadenat and Jacques Blache revisited the type specimens of S. tudes and found that the lectotype from Nice is likely not a smalleye hammerhead, but rather a fetal whitefin hammerhead (S. couardi, likely a synonym of the scalloped hammerhead, S. lewini). [3] [9] This would also explain the anomalous locality of the Nice specimen, as the smalleye hammerhead is not otherwise known outside of the Americas. By the rules of binomial nomenclature, Sphyra tudes should then become the valid name for the whitefin hammerhead, taking precedence over S. couardi, and the smalleye hammerhead would revert to being Sphyrna bigelowi. Taxonomists, though, have been reluctant to change the names again, preferring to keep the smalleye hammerhead as S. tudes. [3] For this solution to have official status would require a decision by the International Commission on Zoological Nomenclature (ICZN), to reject the Nice specimen as the lectotype and designate the Cayenne specimen in its place. The relevant petition to the ICZN has not yet been put forth. [1]

Phylogenetic tree of hammerhead sharks: [10]

Until the first detailed study of the smalleye hammerhead was carried out in 1985–86 by José Castro of Clemson University for the Food and Agriculture Organization of the United Nations, its distinctive golden coloration was unknown to science. The color fades after death, and the pigments leach into the preservative, resulting in the "yellowish cast" of museum specimens being regarded as an artifact of preservation. The names "yellow hammerhead" or "golden hammerhead" are used by fishermen in Trinidad for this shark, and the latter was promoted for wider usage by Castro. [4] [11] Another common name for this species is the curry shark. [1] Phylogenetic analyses based on nuclear and mitochondrial DNA have found that the hammerheads with the smallest cephalofoils are the most derived members of their lineage. The closest relative of the smalleye hammerhead appears to be the scoophead (S. media), and the two of them in turn form a clade with the sister species pair of the scalloped bonnethead (S. corona) and the bonnethead (S. tiburo). [10]

Description

Jaws Sphyrna tudes jaws.jpg
Jaws
Upper teeth Sphyrna tudes upper teeth.jpg
Upper teeth
Lower teeth Sphyrna tudes lower teeth.jpg
Lower teeth

One of the smaller members of its family, the smalleye hammerhead can reach a length of 1.5 m (4.9 ft), [12] though 1.2–1.3 m (3.9–4.3 ft) is more typical, [13] and a weight of 9 kg (20 lb). [11] The body is streamlined and fairly slender. The mallet-shaped cephalofoil is wide and long, with a span measuring 28–32% of the body length; the leading margin forms a broad arch with indentations in the middle and on either side. [14] The cephalofoils of newborns are longer, more arched, and less indented in front than those of adults. [4] The eyes, placed at the ends of the cephalofoils, are proportionately smaller than in other hammerheads and equipped with nictitating membranes (protective third eyelids). [3] [4] The nostrils are positioned just inside of the eyes, each with a well-developed groove running towards the center of the cephalofoil. The mouth is strongly curved, containing on either side 15–16 upper tooth rows and 15–17 lower tooth rows. The teeth have single narrow cusps with smooth or weakly serrated edges, that are angled in the upper jaw and upright in the lower jaw. [3] [14]

The first dorsal fin is tall and slightly falcate (sickle-shaped), originating behind the pectoral fin bases; its free rear tip lies over the origin of the pelvic fins. The second dorsal fin is smaller than the first, but still rather large, with a concave, trailing margin. The pelvic fins have nearly straight trailing margins. The anal fin is taller and longer than the second dorsal fin. The caudal fin has a well-developed lower lobe and a notch near the tip of the upper lobe. [3] The dermal denticles are oval with five horizontal ridges leading to marginal teeth. [15] The most distinctive trait of this species is its coloration; the back and dorsal fins are gray to yellowish gray, and the cephalofoil margins, flanks, underside, pectoral fins, pelvic fins, and anal fin are bright yellow to orange with a metallic or iridescent sheen. Newborn sharks are gray above, darkening on the first dorsal fin and upper caudal fin lobe, and whitish below. They gain a bright yellow cast on their undersides by a length of 45 cm (18 in), which turns to orange by a length of 50 cm (20 in). The golden color is brightest in sharks 55–70 cm (22–28 in) long, and tends to fade with the onset of sexual maturity. [4]

Distribution and habitat

The smalleye hammerhead is found along the eastern coast of South America from Uruguay to Venezuela, though it seldom occurs further west than the Orinoco Delta southeast of Trinidad. [4] Reports of this species from off Panama, Mexico, and western Florida are unconfirmed; records from other parts of the world are most likely erroneous, resulting from its tangled taxonomic history. [1] This species inhabits inshore murky waters 5–40 m (16–131 ft) deep, over muddy bottoms. Segregation occurs by sex and age; newborns and juveniles under 40 cm (16 in) long are found in the shallowest waters, moving deeper after a few months of life. Adult females are mostly found at depths of 9–18 m (30–59 ft), while larger juveniles and adult males are mostly found at depths of 27–36 m (89–118 ft). [4] This species is tolerant of brackish water, and can be found over a salinity range of 20–34 ppt. [16]

Biology and ecology

Four other species of hammerhead sharks overlap in range with the smalleye hammerhead - the small-sized scoophead and bonnethead, and the large-sized scalloped hammerhead and great hammerhead. Little competition occurs between these species because of their differing habitats and dietary preferences. The smalleye hammerhead is the dominant hammerhead in shallow, muddy areas, where high turbidity limits the utility of vision (hence its smaller eyes). Adult males and juveniles of both sexes form schools of uniform body size; these schools do not appear to relate to reproduction or migration. Adult females are apparently solitary. [4] [17]

Young smalleye hammerheads under 67 cm (26 in) long feed predominantly on penaeid shrimp, mostly Xiphopenaeus kroyeri . Larger sharks feed mainly on bony fishes, especially ariid sea catfish and their eggs. The shrimp and the surface mucus layer and eggs of the catfish contain carotenoid pigments that appear to be the source of the sharks' golden color; whether the pigments in the catfish also ultimately come from the shrimp is uncertain. Another shark species in the region, the yellow smooth-hound (Mustelus higmani), also feeds on shrimp and has a yellowish color, albeit not nearly as bright. [4] This species has also been known to consume swimming crabs, squid, grunts, and newborn scalloped hammerheads. [3] The smalleye hammerhead may fall prey to larger sharks such as the bull shark (Carcharhinus leucas), while smaller individuals may also be taken by bony fishes. [15] Its coloration may provide camouflage. [18] A known parasite of this species is the hexabothriid monogenean Erpocotyle schmitti; [19] it may also serve as a host to common copepod ectoparasites such as Echthrogaleus coleoptratus, Pandarus satyrus, and P. cranchii. [15]

Like all hammerhead sharks, the smalleye hammerhead is viviparous: when the developing embryos exhaust their supply of yolk, the depleted yolk sac develops into a placental connection through which the mother delivers nourishment. Mature females have a single functional ovary and two functional uteri. Ovulation occurs at the same time as gestation, allowing females to bear young every year. [4] The details of the smalleye hammerhead's life history vary across its range. [1] Off Trinidad, reproduction occurs on a well-defined annual cycle with mating in August and September, and birthing in late May and June of the following year. The females carry between five and 12 pups for 10 months, and make use of food-rich, shallow coastal bays as nursery areas. The newborns measure around 30 cm (0.98 ft) long, and males and females attain sexual maturity at 80 cm (31 in) and 98 cm (39 in) long, respectively. [4] By contrast, smalleye hammerheads off the northern Brazilian state of Maranhão are substantially larger, with males maturing at over 92 cm (36 in) long and females at over 101 cm (40 in) long. As the litter size increases with female size, Maranhão sharks have been recorded carrying up to 19 pups. The seasonality of breeding also differs, with pregnant females found from June to October and January to April, and males in apparent reproductive condition from May to November and in March. [16]

Human interactions

Timid and harmless to humans, [12] [13] the smalleye hammerhead is caught incidentally by inshore artisanal multispecies fisheries throughout its range, and marketed as food. It is the most or second-most important shark caught by such fisheries off Trinidad and Tobago, Guyana, and Brazil. Because of its head shape, individuals of all ages are readily caught in gillnets; small numbers are also caught on line gear and in bottom trawls. [1] [4] [17] The IUCN assessed this species as critically endangered in 2020, as it is subjected to intense fishing pressure, often without management, by techniques ranging from beach seine netting to trawling, and is unable to replenish this harvest. Smalleye hammerheads are also bycatch in commercial shrimp trawls, which are often run through the shark's shallow-water habitat. Anecdotal evidence suggests that smalleye hammerhead catches have declined significantly off Trinidad and northern Brazil, which are likely indicative of population trends in the rest of its range. The smalleye shark is federally protected in Brazil and Colombia. [1]

Related Research Articles

<span class="mw-page-title-main">Hammerhead shark</span> Family of sharks

The hammerhead sharks are a group of sharks that form the family Sphyrnidae, named for the unusual and distinctive form of their heads, which are flattened and laterally extended into a cephalofoil. The shark's eyes are placed one on either end of this T-shaped structure, with their small mouths directly centered and underneath. Most hammerhead species are placed in the genus Sphyrna, while the winghead shark is placed in its own genus, Eusphyra. Many different— but not necessarily mutually exclusive—functions have been postulated for the cephalofoil, including sensory reception, manoeuvering, and prey manipulation. The cephalofoil gives the shark superior binocular vision and depth perception.

<i>Sphyrna</i> Genus of sharks

Sphyrna is a genus of hammerhead sharks with a cosmopolitan distribution in the world's oceans. Members of Sphyrna have a tendency to inhabit coastal waters along the intertidal zone rather than the open ocean, as their prey such as invertebrates, fish, rays, small crustaceans, and other benthic organisms hide in the sands and sediment along these zones. Members of Sphyrna are also known by synonyms such as Zygaena, Cestracion, and Sphyrichthys. The earliest species described of this genus was Sphyrna zygaena by Carl Linnaeus in 1758, while the latest described member, Sphyrna gilberti, was discovered and described in 2013.

<span class="mw-page-title-main">Great hammerhead</span> Species of shark

The great hammerhead is the largest species of hammerhead shark, belonging to the family Sphyrnidae, attaining an average length of 4.6 m (15 ft) and reaching a maximum length of 6.2 m (20 ft). It is found in tropical and warm temperate waters worldwide, inhabiting coastal areas and the continental shelf. The great hammerhead can be distinguished from other hammerheads by the shape of its "hammer", which is wide with an almost straight front margin, and by its tall, sickle-shaped first dorsal fin. A solitary, strong-swimming apex predator, the great hammerhead feeds on a wide variety of prey ranging from crustaceans and cephalopods, to bony fish, to smaller sharks. Observations of this species in the wild suggest that the cephalofoil functions to immobilize stingrays, a favored prey. This species has a viviparous mode of reproduction, bearing litters of up to 50 pups every two years.

<span class="mw-page-title-main">Winghead shark</span> Species of shark

The winghead shark is a species of hammerhead shark, and part of the family Sphyrnidae. Reaching a length of 1.9 m (6.2 ft), this small brown to gray shark has a slender body with a tall, sickle-shaped first dorsal fin. Its name comes from its exceptionally large "hammer", or cephalofoil, which can be as wide as half of the shark's total length. The function of this structure is unclear, but may relate to the shark's senses. The wide spacing of its eyes grants superb binocular vision, while the extremely long nostrils on the leading margin of the cephalofoil may allow for better detection and tracking of odor trails in the water. The cephalofoil also provides a large surface area for its ampullae of Lorenzini and lateral line, with potential benefits for electroreception and mechanoreception, respectively.

<span class="mw-page-title-main">Smooth hammerhead</span> Species of shark

The smooth hammerhead is a species of hammerhead shark, and part of the family Sphyrnidae. This species is named "smooth hammerhead" because of the distinctive shape of the head, which is flattened and laterally extended into a hammer shape, without an indentation in the middle of the front margin. Unlike other hammerheads, this species prefers temperate waters and occurs worldwide at medium latitudes. In the summer, these sharks migrate towards the poles following cool water masses, sometimes forming schools numbering in the hundreds to thousands.

<span class="mw-page-title-main">Bonnethead</span> Species of shark

The bonnethead, also called a bonnet shark or shovelhead, is a small member of the hammerhead shark genus Sphyrna, and part of the family Sphyrnidae. It is an abundant species in the littoral zone of the North Atlantic and the Gulf of Mexico, is the only shark species known to display sexual dimorphism in the morphology of the head, and is the only shark species known to be omnivorous.

<span class="mw-page-title-main">Blacktip shark</span> Species of shark

The blacktip shark is a species of requiem shark, and part of the family Carcharhinidae. It is common to coastal tropical and subtropical waters around the world, including brackish habitats. Genetic analyses have revealed substantial variation within this species, with populations from the western Atlantic Ocean isolated and distinct from those in the rest of its range. The blacktip shark has a stout, fusiform body with a pointed snout, long gill slits, and no ridge between the dorsal fins. Most individuals have black tips or edges on the pectoral, dorsal, pelvic, and caudal fins. It usually attains a length of 1.5 m (4.9 ft).

<span class="mw-page-title-main">Daggernose shark</span> Species of shark

The daggernose shark is a little-known species of requiem shark, in the family Carcharhinidae, and the only extant member of its genus. It inhabits shallow tropical waters off northeastern South America, from Trinidad to northern Brazil, favoring muddy habitats such as mangroves, estuaries, and river mouths, though it is intolerant of fresh water. A relatively small shark typically reaching 1.5 m (4.9 ft) in length, the daggernose shark is unmistakable for its elongated, flattened, and pointed snout, tiny eyes, and large paddle-shaped pectoral fins.

<span class="mw-page-title-main">Scalloped bonnethead</span> Species of shark

The scalloped bonnethead is a rare, little-known species of hammerhead shark in the family Sphyrnidae. Its other common names include the mallethead shark and the crown shark. It is found in tropical and subtropical waters in the eastern Pacific Ocean, from Mexico to Peru, and possibly as far north as the Gulf of California. It frequents inshore habitats over soft bottoms to a depth of 100 m, and also enters mangroves and estuaries.

<span class="mw-page-title-main">Scoophead</span> Species of shark

The scoophead is a little-known species of hammerhead shark, part of the family Sphyrnidae. It inhabits the tropical waters of the western Atlantic Ocean, from Panama to southern Brazil, and in the eastern Pacific Ocean from the Gulf of California to Ecuador, and probably northern Peru, as well. It is found in shallow, inshore habitats.

<span class="mw-page-title-main">Creek whaler</span> Species of shark

The creek whaler is a common species of requiem shark, and part of the family Carcharhinidae, endemic to northern Australia. It frequents shallow waters close to shore, including estuaries. This small, stocky shark usually grows to 1.0–1.3 m (3.3–4.3 ft) long and is brownish in color without conspicuous fin markings. It can be identified by its long snout, large, triangular pectoral fins, and large, anteriorly positioned first dorsal fin.

<span class="mw-page-title-main">Finetooth shark</span> Species of shark

The finetooth shark is a species of requiem shark, in the family Carcharhinidae, found in the western Atlantic Ocean, from North Carolina to Brazil. It forms large schools in shallow, coastal waters, and migrates seasonally following warm water. A relatively small, slender-bodied shark, the finetooth shark can be identified by its needle-like teeth, dark blue-gray dorsal coloration, and long gill slits. It attains a maximum length of 1.9 m (6.2 ft). The diet of this species consists primarily of small bony fishes, in particular menhaden. Like other members of its family, it is viviparous with females giving birth to two to six pups in estuarine nursery areas every other year.

<span class="mw-page-title-main">Smalltail shark</span> Species of shark

The smalltail shark is a species of requiem shark, and part of the family Carcharhinidae. It is found in the western Atlantic Ocean, from the northern Gulf of Mexico to southern Brazil. It inhabits shallow waters close to shore, particularly over muddy bottoms around estuaries. It tends to swim low in the water column and forms large aggregations segregated by sex. A slim species generally not exceeding 1.1 m (3.6 ft) in length, the smalltail shark has a rather long, pointed snout, a broad, triangular first dorsal fin, and a second dorsal fin that originates over the midpoint of the anal fin base. It is plain gray in color, without prominent markings on its fins.

<span class="mw-page-title-main">Pygmy ribbontail catshark</span> Species of shark

The pygmy ribbontail catshark is a species of finback catshark, family Proscylliidae, distributed patchily in the western Indo-Pacific from Tanzania to the Philippines. It occurs around the edges of continental and insular shelves at a depth of 71–766 m (233–2,513 ft), typically on or near mud bottoms. One of the smallest living shark species, the pygmy ribbontail catshark grows to a maximum known length of 24 cm (9.4 in). It has a slender body with a low, ribbon-like tail fin, and is dark brown in color with blackish dorsal fin markings and tail bands. This shark feeds mainly on bony fishes, followed by crustaceans and then squid. It is aplacental viviparous with females bearing litters of 1–2 relatively large pups. It is of minimal significance to fisheries, being caught as bycatch in some areas.

<span class="mw-page-title-main">Smalleye pygmy shark</span> Species of shark

The smalleye pygmy shark is a little-known species of squaliform shark in the family Dalatiidae, found in water 150–2,000 m (490–6,560 ft) deep near Japan, the Philippines, and Australia. It migrates vertically daily, spending the day in deep water and the night in shallower water. One of the smallest shark species, the smalleye pygmy shark is known to reach only 22 cm (8.7 in) long. It has a blackish, spindle-shaped body with relatively small eyes, and a spine preceding the first dorsal fin, but not the second. Bioluminescent photophores occur on its underside, which may serve to disguise its silhouette from predators. This species feeds on small squid, krill, shrimp, and bony fishes. It is aplacental viviparous. The International Union for Conservation of Nature has assessed it as Least Concern, citing its wide distribution and lack of threat from fisheries.

<span class="mw-page-title-main">Blurred lanternshark</span> Species of shark

The blurred lanternshark is a little-known species of dogfish shark in the family Etmopteridae, found around the world in benthic and pelagic habitats from a depth of 110 m (360 ft) to over 1 km (0.62 mi) down. This shark forms the E. pusillus species group with the smooth lanternshark, which are distinguished from other members of its family by having irregularly arranged, flat-topped dermal denticles that give them a "smooth" appearance. Both species are slender-bodied with long heads, two dorsal fins bearing spines, no anal fins, and light-emitting photophores. The blurred lanternshark is larger, reaching 67 cm (26 in) or more in length. This species feeds on small squid, fishes, and fish eggs, and is ovoviviparous. It has been assessed as of Least Concern by the International Union for Conservation of Nature, because of its wide distribution and lack of threat from fishing pressure.

<span class="mw-page-title-main">Scalloped hammerhead</span> Species of shark

The scalloped hammerhead is a species of hammerhead shark in the family Sphyrnidae. It was originally known as Zygaena lewini. The Greek word sphyrna translates into "hammer" in English, referring to the shape of this shark's head, which is its most distinguishing characteristic. The shark's eyes and nostrils are at the tips of the extensions. It is a fairly large hammerhead, but is still smaller than both the great and smooth hammerheads.

<span class="mw-page-title-main">Carolina hammerhead</span> Species of shark

The Carolina hammerhead is a species of hammerhead shark, and part of the family Sphyrnidae, found in the western Atlantic Ocean. Their pupping grounds are in nearshore waters off the southeastern U.S. with the highest concentrations found in Bulls Bay, South Carolina. The Carolina hammerhead has also been found in nearshore waters off of Brazil. It was formally described in 2013. It is currently classified as Vulnerable (VU) on the IUCN Red List due to overfishing and habitat degradation.

References

  1. 1 2 3 4 5 6 7 Pollom, R.; Barreto, R.; Charvet, P.; Chiaramonte, G.E.; Cuevas, J.M.; Faria, V.; Herman, K.; Lasso-Alcalá, O.; Marcante, F.; Mejía-Falla, P.A.; Montealegre-Quijano, S.; Motta, F.; Navia, A.F.; Nunes, J.; Paesch, L.; Rincon, G. (2020). "Sphyrna tudes". IUCN Red List of Threatened Species . 2020: e.T60202A3091946. doi: 10.2305/IUCN.UK.2020-3.RLTS.T60202A3091946.en . Retrieved 19 November 2021.
  2. ↑ "Appendices | CITES". cites.org. Retrieved 14 January 2022.
  3. 1 2 3 4 5 6 7 8 9 Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Food and Agricultural Organization of the United Nations. pp. 551–553. ISBN   92-5-101384-5.
  4. 1 2 3 4 5 6 7 8 9 10 11 12 Castro, J.I. (1989). "The biology of the golden hammerhead, Sphyrna tudes, off Trinidad". Environmental Biology of Fishes. 24 (1): 3–11. doi:10.1007/BF00001605. S2CID   12510936.
  5. ↑ Valenciennes, A. (1822). "Sur le sous-genre Marteau, Zygaena". Mémoires du Muséum National d'Histoire Naturelle. 9: 222–228.
  6. ↑ Springer, S. (1944). "Sphyrna bigelowi, a new hammerhead shark from off the Atlantic coast of South America, with notes on Sphyrna mokarran from New South Wales". Journal of the Washington Academy of Sciences. 34 (8): 274–276.
  7. ↑ Tortonese, E. (1950). "A note on the hammerhead shark, Sphyrna tudes Val. after a study of the types". Annals and Magazine of Natural History. 3 (36): 1030–1033. doi:10.1080/00222935008654116.
  8. ↑ Gilbert, C.R. (1967). "A revision of the hammerhead sharks (family Sphyrnidae)". Proceedings of the United States National Museum. 119 (3539): 1–88. doi:10.5479/si.00963801.119-3539.1.
  9. ↑ Cadenat, J. & Blache, J. (1981). Requins de Méditerranée et d'Atlantique. Editions de l'Office de la recherche scientifique et technique outre-mer. pp. 298–300. ISBN   2-7099-0576-0.
  10. 1 2 Lim, D.D.; Motta, P.; Mara, K.; Martin, A.P. (2010). "Phylogeny of hammerhead sharks (Family Sphyrnidae) inferred from mitochondrial and nuclear genes". Molecular Phylogenetics and Evolution. 55 (2): 572–579. doi:10.1016/j.ympev.2010.01.037. PMID   20138218.
  11. 1 2 Martin, R.A. (August 4, 1998). In Search of the Golden Hammerhead. ReefQuest Centre for Shark Research. Retrieved on October 17, 2008.
  12. 1 2 Froese, Rainer; Pauly, Daniel (eds.) (2008). "Sphyrna tudes" in FishBase. January 2008 version.
  13. 1 2 Ferrari, A. & A. Ferrari (2002). Sharks. Firefly Books. p.  192. ISBN   1-55209-629-7.
  14. 1 2 McEachran, J.D. & Fechhelm, J.D. (1998). Fishes of the Gulf of Mexico: Myxiniformes to Gasterosteiformes. University of Texas Press. p. 96. ISBN   0-292-75206-7.
  15. 1 2 3 Gallagher, E. Biological Profiles: Smalleye Hammerhead. Florida Museum of Natural History Ichthyology Department. Retrieved on April 23, 2010.
  16. 1 2 Lessa, R.; Menni, R.C. & Lucena, F. (September 1998). "Biological observations on Sphyrna lewini and S. tudes (Chondrichthyes, Sphyrnidae) from northern Brazil". Vie et Milieu. 48 (3): 203–213.
  17. 1 2 Léopold, M. (2004). Poissons de mer de Guyane. Editions Quae. pp. 32–33. ISBN   2-84433-135-1.
  18. ↑ Belleville, B. (2004). Sunken Cities, Sacred Cenotes & Golden Sharks: Travels of a Water-Bound Adventurer . University of Georgia Press. pp.  168–176. ISBN   0-8203-2592-9.
  19. ↑ Suriano, D.M. & Labriola, J.B. (January 1998). "Erpocotyle VanBeneden et Hesse, 1863 (Monogenea, Hexabothriidae), parasite of carcharhiniform fishes from the southwestern Atlantic Ocean, with the description of E. schmitti sp. n". Acta Parasitologica. 43 (1): 4–10.

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