Jaggedly radiating outwards in a spiral, the teeth in this beautiful jaw have been preserved for 290 million years in rock. What is it though? It is well known to beach combers that sharks have teeth that regenerate, but modern sharks teeth come in in rows. This spiral design, with older teeth on the outer spiral and newer ones in the center, is completely novel and no longer extant.
This puzzling specimen is a helicoprion fossil - one of a genus of “spiral saw” cartilaginous fish. Basically shark-like, these crazy denizens of the deep have mystified researchers for years as they try to figure out how on earth the spiraling teeth were used and situated on the beast. According to wikipedia (source of champions) and verified on the Smithsonian website, the spiral was coiled on or within the lower jaw. The currently accepted reconstruction, made by scientific illustrator Mary Parrish with the input of scientists in the paleobiology department at NMNH, is based on several fossils that have varying degrees of cartilage preservation and teeth formation and places the teeth within the shark’s mouth attached to the lower jaw. This guess though is only the best science can currently offer: the true orientation of the teeth and their location in the jaws of these Permian sharks is still a mystery.