Hammerhead shark

The Hammerhead shark is a member of class Chondrichthyes like the other sharks (order Carcharhiniformes, family Sphyrnidae, genus Sphyrna). (The only other genus of Sphyrnidae, Eusphyra contains only one species, E. blochii, the winghead shark). Species of hammerhead range from 2-6 m long; projections on both sides of the head give these sharks a resemblance to a flattened hammer. The shark's eyes and nostrils are at the tips of the extensions. It is an aggressive predator that eats fish, rays and other sharks, cephalopods, and crustaceans. It is found in warmer waters along coastlines and continental shelves.

Of the eight species of hammerhead, three can be dangerous to humans - the scalloped, great and smooth hammerheads.

Genus Sphyrna

Subgenus Sphyrna

Species: lewini (scalloped), mokarran (great), zygaena (smooth)

Subgenus Mesozygaena

Species: corona (scalloped bonnethead)

Subgenus Platysqualus

Species: media (scoophead), tiburo (bonnethead), tudes (smalleye)

Sharks do not have mineralized bones and rarely fossilize, but their teeth are frequently found as fossils. The hammerheads are closely related to the Carcharhinid sharks that evolved during the mid Tertiary. The teeth of hammerheads resemble those of some Carcharhinids, making it difficult to be certain when the hammerheads first appeared. It is probable that the hammerheads evolved during the late Eocene, Oligocene or early Miocene.