That is the correct spelling of "ammonite" (a prehistoric
mollusc, a marine snail).
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An ammonite is an explosive prepared from ammonium nitrate, or any of a group of extinct cephalopods of the family Ammonoidea.
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Ammonite shells. A fossil that looks like a spiral or a rams horns is called an ammonite. Ammonites is extinct group of marine invertebrate animals that appeared during the Devonian period.