this might look like a circular saw to you but actually this belongs to an extinct shark-like fish that lived over 250 million years ago this is the helicoprion helicoprion is an extinct cartilagenous fish it had a jaw-dropping feature that still baffles scientists today a spiral saw likee row of teeth this spiral of teeth is known as tooth whs which contain over 100 serrated teeth and it's so weird that it left scientists baffled for over a century but what we understand today is that the teeth were used for feeding and were located at the bottom Jaw from a fossil that was found in Idaho in 1950 and it's the only example we have with the skeletal elements remained intact these spiral teeth are about the only thing that remain from this creature because helicoprion skeletons were made mostly of cartilage similar to sharks so most of their tissues would disintegrate before they had a chance to fossilize