ammonoid

[ am-uh-noid ]

noun

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

ammonoid

/ ăm′ə-noid′ /

1. 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.

Word History and Origins

Origin of ammonoid¹

1880–85; < New Latin Ammonoidea, equivalent to Ammon ( ites ) name of the order + -oidea -oidea; ammonite ²

Example Sentences

He noted that "most ammonoid conchs were coiled and had chambers. The chamber walls were vaulted," meaning they had arches, starting "a little in the middle and increasingly vaulted outward."

From Salon

Well, its whorl's similarity in appearance to ammonoids was actually a clue: the shape made it good for snagging ammonoid flesh and then ripping them out of their shells.

From Scientific American

Late in the succeeding Carboniferous period appear shells with a truly ammonoid complexity of sutures, and in the Permian their number and variety cause them to form a striking element of the marine faunas.

From Project Gutenberg