ammonoid

[ am-uh-noid ]
/ ˈæm əˌnɔɪd /

noun

any cephalopod mollusk of the extinct order Ammonoidea, from the Devonian to the Cretaceous periods, having a coiled, chambered shell.

Origin of ammonoid

1880–85; < New Latin Ammonoidea, equivalent to Ammon(ites) name of the order + -oidea -oidea; see ammonite2

Words nearby ammonoid

ammonium thiocyanate, ammonium thiosulfate, ammoniuria, ammono, ammono-, ammonoid, ammonolysis, ammonolyze, ammons, ammophilous, ammunition

Scientific definitions for ammonoid

ammonoid
[ ăm′ə-noid′ ]

Any of various extinct cephalopods of the subclass Ammonoidea living from the Devonian to the Cretaceous Periods. Ammonoids had a symmetrical, coiled, chambered shell with angular sutures between the chambers. They are closely related to the nautiloids, including the modern-day chambered nautilus.