Ammonoidea

plural noun

Am·​mo·​noi·​dea

ˌaməˈnȯidēə

: 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 entry 1

ammonoidean

¦amə¦nȯidēən

adjective or noun

Word History

Etymology

New Latin, irregular from Ammonites + -oidea

First Known Use

1884, in the meaning defined above

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