Ammonite — extinct spiral-shelled marine cephalopods Ammonite Extinct marine cephalopods of subclass Ammonoidea, known for coiled, chambered shells. Their fossils are widespread and important index fossils; closest living relatives are modern…
Belemnites: extinct Mesozoic coleoids with a fossil rostrum Belemnite Belemnites were squid-like marine cephalopods of the Mesozoic known for their bullet-shaped calcitic rostra; they had ten arms, an ink sac, and are important index fossils and pale…
