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Ammonoidea
plural noun
Am·mo·noi·dea
\ˌaməˈnȯidēə\
Definition of Ammonoidea
: an order of extinct chiefly Mesozoic Tetrabranchia comprising cephalopods having an external chambered shell that is either straight or variously curved or coiled — see ammonite
ammonoidean
\¦amə¦nȯidēən\ adjective or nounFrom the M-W Editors
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Origin and Etymology of ammonoidea
New Latin, irregular from Ammonites + -oidea
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