Known as the Spiral Saw, the Helicoprion is said to have lived during the Carboniferous period and was one of the few creatures able to live through the Permian-Triassic extinction event (‘The Great Dying’). Eventually the Helicoprion went extinct during the Triassic period. Though not many fossils have been found, archaeologists have found the tooth-whorl as well as jaw bones. With these, researchers have pieced together ideas of what the Helicoprion may have looked like. One thing we know for sure is that the creature had teeth that are very much like a circular saw, which was connected on the lower jaw. It had so many teeth because as new teeth grew, the older teeth were pushed out and into the middle to create the spiral. Length-wise the creature was said to be 10-15 feet.
The Helicoprion was said to be extremely shark-like, having cartilage, fins, and razor sharp teeth. In fact, some believe that the creature was a shark itself, but there is not enough evidence to prove this.