Helicoprion, one of the most famous and unusual shark relatives that lived before the Mesozoic era, is classified as a "chimaera," a family of fishes that are somewhat related to sharks but are not sharks themselves. The purpose of the dental spiral on its lower jaw remains a matter of debate. Personally, I believe that, along with the body parts of small prey, Helicoprion may have "shed" or swallowed worn teeth, and the spiral would gradually "unwind," pushing still-healthy teeth to the outer edge of the spiral. Depending on the species, Helicoprion ranged in size from 5-8 to 10-12 meters long