Together with ammonites, belemnites are the most frequently found fossils in Posidonia shale. Usually, the only fossilised remains of belemnites are the rear hard tissue, or rostrum.
This is made up of fibrous calcite. In the living animal, it was surrounded by muscle and served as a supporting endoskeleton. The belemnites of the Jurassic period grew to a maximum length of 50 centimetres. The males can be readily distinguished from the females by their two large hooks in the crown.
In terms of anatomy and way of life, these cephalopods probably resembled today’s cuttlefish, especially squid.