ammonite(redirected from Ammonoidea)
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1. An extinct cephalopod mollusk of the order Ammonitida of the Permian to Cretaceous Periods, having a thick, usually coiled shell characterized by intricate suture patterns where the septa between individual chambers join the outer shell wall.
2. An ammonoid.
am′mo·nit′ic (-nĭt′ĭk) adj.