A belemnite is an extinct marine creature that lived during the Mesozoic era, around 200 to 65 million years ago. These fascinating animals are related to modern-day squid and cuttlefish. Belemnites had a bullet-shaped shell, which is often found as fossils today. Their unique shape helped them swim efficiently in the oceans of their time. Belemnites were part of the class Cephalopoda, which includes other intelligent sea creatures. They were predatory animals, feeding on smaller fish and invertebrates. The fossilized remains of belemnites provide valuable information about ancient marine ecosystems and help scientists understand the evolution of cephalopods.