Sphyrna

Great hammerhead ( Sphyrna mokarran )

Sphyrna is a genus of hammerhead sharks ( Sphyrnidae ) that contains all the species of the family with the exception of the wing head - Hammerhead ( Eusphyra blochii ). It comprises eight species and is found on all tropical and subtropical coasts. Four species of this genus are also found in the Mediterranean.

Appearance and characteristics

The Sphyrna species are medium to large sharks; the body lengths ranging from about 90 centimeters at the corona hammerhead ( Sphyrna corona ) up to about 6 meters at the great hammerhead ( Sphyrna mokarran ). Characteristic is the hammer -like enlargement of the head ( Cephalofoil ) whose ends are the eyes and on the front edge there is another effective sensory organ with the Lozenzinischen ampoules. This head is moved outwards in the species of this genus between 17 and 33 percent of the total length, the wing head Hammerhead ( Eusphyra blochii ) even 40 to 50 percent. With the exception of head shape to correspond to in habit the requiem sharks ( Carcharinidae ) and how these have 5 gill slits during an injection hole is missing. They also have an anal fin and two dorsal fins, of which the front is larger than the rear.

Way of life

Sphyrna species live mainly as a shallow water species, especially over the continental shelf or other shallow marine areas. The scalloped hammerhead ( Sphyrna lewini ) and the great hammerhead can be found in the water column, however, even in the open ocean, while nonetheless always present in relative coast. All Sphyrna species feed mainly on bony fishes, with especially the great hammerhead also attacks many other marine species as opportunistic hunters and also eats carrion.

The sharks are viviparous and form a yolk sac placenta ( placental viviparous ).

Dissemination

The hammerhead sharks of the genus Sphyrna are found in all tropical and subtropical coastal areas. Here, some species occur in very large areas such as the Great Hammerhead, which is common in all tropical and subtropical coastal areas. Other species are restricted to regional distribution areas, so there is the white fin hammerhead ( Sphyrna couardi ) only to the Atlantic coasts of Europe and North West Africa and the bonnethead hammerhead ( Sphyrna tiburo ) only from the tropical shores of the Americas. The smallest area of ​​distribution has the corona Hammerhead, which is widespread on the Pacific coast of America from the Gulf of California to Peru

System

The genus Sphyrna consists of eight recognized species:

  • Corona hammerhead ( Sphyrna corona ), Springer, 1940
  • Spoon head Hammerhead ( Sphyrna media), Springer, 1940
  • Bonnethead hammerhead ( Sphyrna tiburo ), Linnaeus, 1758
  • Smalleye hammerhead ( Sphyrna tudes ), Valenciennes, 1822
  • Scalloped Hammerhead, also Notched Hammerhead ( Sphyrna lewini ), Griffith & Smith, 1834
  • Great hammerhead ( Sphyrna mokarran ), Rüppell, 1837
  • Smooth hammerhead ( Sphyrna zygaena ), Linnaeus, 1758
  • Sphyrna gilberti ( Gilbert Hammerhead ), Quattro et al., 2013

The listed as a separate species in older literature white fin hammerhead ( Sphyrna couardi ), was established in 1986 synonymized with the scalloped hammerhead.

Constantine Samuel Rafinesque Scalloped bonnethead Ampullae of Lorenzini Fish fin FishBase Digital Object Identifier
741531
de