Lacking swim bladders, which most bony fishes use to regulate buoyancy, they may have lost bone as one means of achieving more neutral buoyancy. Instead of a swim bladder, sharks have large, oil-filled livers that give them buoyancy.
Sharks shed their teeth throughout their lives, so fossil shark teeth are common in some places.
Scientists think that having their nostrils separated helps hammerheads to better follow the direction of a scent trail. A hammerhead can detect a slight change in the concentration of a scent between the two nostrils. The shark's electroreceptor organs are also widely spread, perhaps increasing their sensitivity. And their eyes sit out on the ends of their head, giving them extremely good binocular vision. It is possible that the broadened head also provides additional lift.