ˌaməˈnȯidēə noun plural
Usage: capitalized
Etymology: New Latin, irregular from Ammonites + -oidea
: 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 I
• am·mo·noi·de·an |amə|nȯidēən adjective or noun