belemnite

Etymology

From Ancient Greek βέλεμνον (bélemnon, “dart, arrow”) + -ite.

noun

1. (paleontology) Any member of the extinct order †Belemnitida of Mesozoic marine cephalopods, very similar in many ways to the modern squid and closely related to the modern cuttlefish.
   In the universal decay this volatile substance had chanced to survive, perhaps through many thousands of centuries. It reminded me of a sepia painting I had once seen done from the ink of a fossil Belemnite that must have perished and become fossilized millions of years ago. 1895, H. G. Wells, chapter VIII, in The Time Machine
   The guts of fossilized marine reptiles are packed with belemnites, and it's been theorized that some prehistoric sharks even died from the overconsumption of heavy belemnite shell guards. 2017, Danna Staaf, Squid Empire, ForeEdge, page 101