hammerhead shark Sphyrna zygaena, a remarkable member of the shark family whose most noticeable characteristic is the T-shaped head, with eyes at the extremities. This is a very large fish (maximum length 4 m/160") and a viviparous one; the mother may give birth to two or three dozen infant hammerheads, each already about 50 cm (20") long. The species has a circumglobal distribution, including the Mediterranean, the E. Atlantic from Senegal to the English Channel, western parts of the Indian Ocean, and temperate waters in the Pacific.
