The Bonnethead or Shovelhead, Sphyrna tiburo, is a member of the hammerhead shark genus Sphyrna. The Greek word sphyrna translates as hammer, referring to the shape of this shark's head - tiburo is the Taino word for shark.


Characterized by a broad, smooth, spade-like head, they have the smallest cephalofoil (hammerhead) of all Sphyrna. Grey-brown above and lighter on the underside, it is a timid and a harmless shark. On average, bonnethead sharks are about 3–5 ft (0.91–1.5 m) long, being one of the smallest hammerhead shark.


This species lives in the Western Hemisphere where the water is usually warmer than 70 °F (21 °C). During the summer it is common in the inshore waters of the Carolinas and Georgia; in spring, summer, and fall, it is found off Florida and in the Gulf of Mexico. In the winter, the bonnethead shark is found closer to the equator, where the water is warmer.


The bonnethead shark is an active tropical shark that swims in small groups of 5 to 15 individuals. Curiously however, schools of hundreds or even thousands have been reported. Bonnethead sharks move constantly following changes in water temperature and to maintain respiration. The bonnethead shark will sink if it does not keep moving since hammerhead sharks are among the most negatively buoyant of marine vertebrates. The bonnethead shark uses a special body fluid, called "cerebrospinal fluid" or "Cl-excess to let others know it is nearby. Like other sharks it is capable of electroreception to detect its preys. This system allows the bonnethead shark to position itself for biting prey within a few feet where its eyes are least able to assist.


It feeds primarily on crustaceans, consisting mostly of blue crabs, but also shrimp, mollusks and small fish. Seagrasses have been found in its stomach contents.