The most distinctive feature of the hammerhead shark is also the one that scientists have struggled to explain: the shark's bizarre head anatomy, with its flattened snout and widespread eyes.
Researchers have put forth a number of theories for why the oddly shaped heads evolved. One recent study confirmed that the eye arrangement does give the shark a vision advantage. Not only does it have binocular vision like humans, where its two fields of vision overlap, but by swinging its head to and fro it can see through 360 degrees of vision.
Other researchers have suggested that the head acts as a hydrofoil to help the shark swim, or that the shark benefits from having chemical, electrical, and pressure sensors spread out along the head's leading edge.