Also known as “spiral saw,” this shark-like cartilaginous fish first arose in the oceans of the late Carboniferous era. However, the only surviving evidence of its existence was a tight curled-up coil of triangular teeth. This bizarre structure was attached to the bottom part of its jaw, though how it was used still remains a mystery today. Some speculations are that it was used to grind shells, while others believed that the coil could be unfurled like a whip to spear unfortunate prey.