belemnieten

Belemnites are extinct marine cephalopods belonging to the subclass Coleoidea, commonly known as belemnites. They lived during the Mesozoic era, particularly from the Jurassic to the Cretaceous periods. These organisms are characterized by their distinctive internal shell, called a rostrum or guard, which is often preserved as a fossil. The rostrum is a hollow, conical structure that served as a counterweight for the animal's buoyancy control, aiding in vertical movement in the water column. Belemnites were nektonic, meaning they were active swimmers, and likely preyed on smaller marine organisms. Their fossils are widely distributed across the globe, providing valuable insights into Mesozoic marine ecosystems and evolutionary relationships among cephalopods. The group became extinct at the end of the Cretaceous, around 66 million years ago, coinciding with the mass extinction event that also wiped out non-avian dinosaurs.