Belemnites (or belemnoids) are an extinct group of marine creatures, very similar in squid and closely related to the modern cuttlefish. Like squid and cuttlefish, belemnites had an ink sac, but unlike the squid, they have no tentacles. Instead, they possessed ten arms of roughly equal length. Unlike the modern squid, whose arms have suckers, belemnite arms carried a series of small hooks for grabbing prey.
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Belemnites were efficient carnivores that caught small fish and other marine animals with their arms and ate them with their beak-like jaws. In turn, belemnites appear to have formed part of the diet of marine reptiles such as Ichthyosaurs, whose fossilized stomachs frequently contain many phosphatic hooks from the arms of cephalopods.
Belemnites became extinct along with Ammonites.