hammerhead shark - Reproduction, Species

Large, active shark of inshore tropical and temperate waters, characterized by a flattened head with broad lateral lobes which are thought to aid manoeuvrability; eyes and nostrils widely spaced; includes the great hammerhead of tropical Atlantic waters (Sphyrna mokarran), length up to 6 m/20 ft. (Genus: Sphyrna. Family: Sphyrnidae.)

iHammerhead sharks
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Chondrichthyes Subclass: Elasmobranchii Order: Carcharhiniformes Family: Sphyrnidae Genus: Sphyrna Rafinesque, 1810
Species
See text.

Sharks Portal

Hammerhead sharks of the genus Sphyrna are members of the family Sphyrnidae.

Reproduction

Reproduction in the hammerhead shark occurs once a year and each litter contains 20 to 40 pups. Unlike many other shark species, the hammerhead shark has internal fertilization which creates a safe environment for the sperm to unite with the egg.

Species

Of the nine known species of hammerhead, three can be dangerous to humans: the scalloped, great, and smooth hammerheads. Smith, 1834) "Cryptic scalloped hammerhead" -- Scalloped hammerheads turn out to be divided into two separate species, which have not been officially reclassified with separate names. Great hammerhead, Sphyrna (Sphyrna) mokarran (Rüppell, 1837) Smooth hammerhead, Sphyrna (Sphyrna) zygaena (Linnaeus, 1758) Whitefin hammerhead, Sphyrna (Sphyrna) couardi Cadenat, 1951 Subgenus Mesozygaena Scalloped bonnethead, Sphyrna (Mesozygaena) corona Springer, 1940 Squarehead Shark Sphyrna (Mesozygaena) sp. listed on elasmo-research's list Subgenus Platysqualus Scoophead, Sphyrna (Platysqualus) media Springer, 1940 Bonnethead or shovelhead, Sphyrna (Platysqualus) tiburo (Linnaeus, 1758) Smalleye hammerhead, Sphyrna (Platysqualus) tudes (Valenciennes, 1822)

Announcements in June, 2006 reported the discovery of a possible new species of hammerhead off the shores of South Carolina. Because the teeth of hammerheads resemble those of some carcharhinids, it has been difficult to determine when hammerheads first appeared.

Geneticist Andrew Martin used DNA to study all hammerhead species and he concluded that the first hammer appeared on the winghead shark, which has the largest hammer, and the rest of the hammerhead sharks evolved one at a time from the original winghead shark each with a smaller hammer .