The Helicoprion Was A Shark With A Buzzsaw In Its Mouth

Helicoprion was a shark species known only by the fossils of its terrifying teeth, and it was possibly one of the most unusual and horrifying monsters to ever menace the sea. Sharks are cartilaginous, which means they lack fossilizable bones, hence most extinct sharks are known solely by what was in their jaws. For years, scientists battled to explain Helicoprion's teeth' distinctive spiral structure.

It was always thought that the extinct shark had a buzzsaw-shaped mouth, but a new study indicates that the teeth were actually located inside Helicoprion's lower jaw.