Assertion: cephalopod's form | /r/RelatedTo | modern nautilus
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Source sentences:
text: Ammonoid, also called ammonite, any of a group of extinct cephalopods (of the phylum Mollusca), forms related to the modern pearly nautilus (Nautilus), that are frequently found as fossils in marine rocks dating from the Devonian Period (began 419 million years ago) to the Cretaceous Period (ended 66 million years ago).