The distinctive shaped hammer head of these ocean predators is called a cephalofoil, and it has some small variations among the different species of hammerheads. The great hammerhead has a cephalofoil that's broad and nearly flat across the front, with a single shallow notch in the center. The scalloped hammerhead is arched more and has a pronounced center notch with two matching notches on either side, giving it a scalloped appearance. The smooth hammerhead is, you guessed it, smooth -- no notches and just a slight, broad arch. The bonnethead's cephalofoil is distinct from the others. It's rounded at the front and resembles a shovel more than a hammer.
But why do these sharks have such on oddly shaped head? Researchers aren't 100 percent sure why they evolved this way, but they have a few different theories, some of which hold up well under research. The first is that it acts as a lift when swimming, much like an airplane wing. Research indicates that while hammerheads have better maneuvering capabilities than other sharks, it's not likely due to the cephalofoil. They're more flexible and can therefore turn and pivot more easily with greater speed.
Another theory is that the hammerhead uses its cephalofoil to aid in trapping prey. One of the hammerhead's favorite foods is the stingray. Once a ray is located, the hammerhead pins the ray to the ground with its cephalofoil and starts eating. This theory has been observed in the wild, but it's probably a learned technique and not the central reason for the wide cephalofoil.
The most likely explanation is that the cephalofoil increases the hammerhead's ability to sense prey. All sharks have electrical sensors in their nose and heads called ampullae of Lorenzini, named for researcher Stephan Lorenzini. These sensors can detect weak electric emissions from other sea life. Because hammerheads have broad, flat heads, the ampullae are spread out over a greater surface area, giving the shark the ability to cover more ground and sense its prey easier. This theory is bolstered by the hammerhead's tendency to troll the bottom of the floor and its ability to find camouflaged stingrays buried beneath the sand.
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