The Digital Fish Library

Distribution:
Tropical to warm temperate waters worldwide.

Habitat:
Over continental and insular shelves, occasionally in brackish water.

Remarks:
The Hammerhead Sharks are so-named for the prominent lateral extensions, or cephalofoil, on the head. There are a diversity of head morphologies within this family. When viewed from above or below, the head extensions may range from being extremely long and narrow as in Eusphyra blochii (the winghead) to being scalloped as in Sphyrna lewini (the Scalloped Hammerhead), or even short and spadelike as in Sphyrna tiburo (the bonnethead).

The evolutionary reason for the cephalofoil is unclear, however several possiblities include 1) greater sensitivity to electric fields (with increased length of ampullae of Lorenzini tubules), 2) increased olfactory capabilities (with large prenarial groove), 3) enhanced hydrodynamics and maneuverability (similar to that of a hydrofoil) and 4) prey manipulation and hunting. The eyes of sphyrnid sharks are spaced farther apart than all other sharks, and it was originally believed that this greater spacing might allow the hammerhead a broader visual field or binocular vision, however research at Florida Atlantic University indicates that instead this large spacing creates a blind spot at the tip of the hammerhead snout.

Adult hammerheads may be aggressive and dangerous. There are a number of recorded human fatalities.

This family comprises 2 genera (Eusphyra and Sphyrna), and eight species.

References:
Nelson 2006; FAO Compagno; Elasmobranch Research Laboratory 2007