<Tr> <Td_colspan="2"> <Ul> <Li> Eusphyra </Li> <Li> Sphyrna </Li> </Ul> </Td> </Tr> <Ul> <Li> Eusphyra </Li> <Li> Sphyrna </Li> </Ul> <P> The hammerhead sharks are a group of sharks in the family Sphyrnidae, so named for the unusual and distinctive structure of their heads, which are flattened and laterally extended into a "hammer" shape called a cephalofoil . Most hammerhead species are placed in the genus Sphyrna, while the winghead shark is placed in its own genus, Eusphyra . Many, but not necessarily mutually exclusive functions have been proposed for the cephalofoil, including sensory reception, manoeuvering, and prey manipulation . Hammerheads are found worldwide in warmer waters along coastlines and continental shelves . Unlike most sharks, hammerheads usually swim in schools during the day, becoming solitary hunters at night . Some of these schools can be found near Malpelo Island in Colombia, Cocos Island off Costa Rica, and near Molokai in Hawaii . Large schools are also seen in the waters off southern and eastern Africa . </P> <P> The known species range from 0.9 to 6.0 m (3.0 to 19.7 ft) in length and weigh from 3 to 580 kg (6.6 to 1,278.7 lb). They are usually light gray and have a greenish tint . Their bellies are white which allows them to blend into the ocean when viewed from the bottom and sneak up on their prey . Their heads have lateral projections which give them a hammer - like shape . </P>

Where did the hammerhead shark get its name