Helicoprion

Helicorprion also known as "the spiral saw" is said to have lived during the carboniferous period and one of the few creatures able to live through the Permian-Triassic extinction or so called "the great dying".Eventually  Helicoprion extinct during the Triassic period.Though not many fossils were found. Archaeologist 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 has teeth that are very much like circular saw, which was connected on the lower jaw. It has many teeth because as new teeth grew, the older ones get pushed out and into the middle to create the spiral. Length-wise is said to be about 10-15 feet. What a bizarre creature.

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.