noun - Hammerhead sharks are a group of sharks in the family Sphyrnidae. They are named for the unusual and distinctive structure of their heads, which are flattened and laterally extended into a hammer shape called a cephalofoil. 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, near Molokai Island in Hawaii, and Yonaguni Island in Okinawa, Japan. Large schools are also seen in southern and eastern Africa.