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Belemnites is an extinct group of coleoid cephalopods with an internal shell composed of rostrum, phragmocone, and pro-ostracum. The oldest belemnites are known from the Late Triassic (210 Ma), and the last ones became extinct at the Cretaceous-Tertiary (K/T boundary) (66 Ma). The initial chamber (protoconch) is relatively large and spherical. The phragmocone is divided by septa into dense chambers and protected by the rostrum. Tiny fins were attached to the rostrum. Belemnites possessed ten arms with hooks, modern jaws, and well-developed ink-sac. The largest animals exceeded a length of 2,5 meters (including arms). ## Keywords Mesozoic, Triassic-Cretaceous, coleoid cephalopods, order Belemnitida
