Belemenites

Belemnitids are an extinct group of prehistoric cephalopods from the Mesozoic seas, existing around the same time as the dinosaurs, from the mid Triassic (250 mya) to the Late Cretaceous (65 mya). They very closely resemble modern day squids, but unlike squids possessed an internal skeleton. The pointy guard on the tops of their body was calcitic and extremely dense, leading to these being the most common body part of theirs to fossilize. They ranged from 2 inches to nearly 2 feet long.