Coronal and ventral x-rays of the hammerhead shark, Sphyrna mokarran.
The distinguishing feature of this animal is, of course, the highly unusual skull shape. You may once have wondered what exactly this seemingly clumsy structure contributes to this fearsome predator, and biologists still do. However, a number of theories exist to explain this unique adaptation; here are some of the best:
- All the better to see you with: mounting the eyes at either end of the broad skull allows excellent vision in all areas of the vertical plane. Hammerhead sharks, as hunters of bottom-dwelling animals, can use this superior angle of vision to better locate prey.
- Another pair of fins. The head has evolved into the shape of an effective hydrofoil. It is thought that this may provide greater stability to the shark when making sharp turns and hunting.
- Heartbeat sensor. Like many sharks, the hammerhead possesses specialised electrosensory organs called the ampullae of Lorenzini. With these, it can detect the magnetic activity of the Earth and find its heading by means of biological compass. Much more impressively, the hammerhead can detect the minuscule electrical activity emitted by the muscle contractions of its prey, allowing location even when hidden from sight. Almost like a skull-mounted metal detector, the shark may sweep the seabed. All it takes is a heartbeat to give the game away.
Photo credit to Dan Anderson.