East Riding Museums

Several examples of fossil belemnites (Hibolites Iaculum), black, grey and dark brown. From Speeton clay. Belemnites were small tentacled sea creatures (a member of the cephalopod group), which lived during the Mesozoic period (about 248-66 million years ago). In antiquity these fossils were popularly known as "thunderbolts", since it was thought they had been flung out of the sky during thunderstorms. The long, bullet-shaped shell of the creatures was made of calcite (calcium carbonate).