This illustration shows one old idea of what the ancient shark Helicoprion might have looked like. There was room for many ideas—some more plausible than others—because the only fossils of the fish were of a strange, spiral-shaped jaw loaded with teeth. Where did it go? In its mouth, on its nose, or its head? A study published in 2013 finally cleared up the mystery: the spiral is completely embedded in the shark's lower jaw and serves as it's full toothset, unlike the sharks drawn here, which have full jaws in addition to the toothy whorl. Read more about this finding in our Great White Shark featured story.