ammonite

1 of 2

noun (1)

am·​mo·​nite ˈa-mə-ˌnīt 

: any of a subclass (Ammonoidea) of extinct cephalopods especially abundant in the Mesozoic age that had flat spiral shells with the interior divided by septa into chambers

ammonitic

ˌa-mə-ˈni-tik 

adjective

Illustration of ammonite

Ammonite

2 of 2

noun (2)

Am·​mon·​ite ˈa-mə-ˌnīt 

: a member of a Semitic people who in Old Testament times lived east of the Jordan between the Jabbok and the Arnon

Ammonite adjective

Examples of ammonite in a Sentence

Recent Examples on the Web

Noun

The site's paleontological importance is underscored by the presence of fossils found in the sedimentary layers, including ammonites, marine reptiles and microorganisms, all of which provide critical insight into life before and after the extinction event. —Jonathan Granoff, Newsweek, 29 Jan. 2025

Most commonly seen in marine fossils, such as ammonites or trilobites, pyritization can produce highly detailed, metallic-looking fossils that are both scientifically valuable and visually striking. —Nina Turner, Newsweek, 29 Oct. 2024

The exhibition achieves that goal with a thoughtful and heady combination of nearly 200 scientific and literary publications; artworks; and loans, including ammonites, trilobites and a cast of an ichthyosaurus skull. —Anne Wallentine, Smithsonian Magazine, 8 Oct. 2024

Other mosasaur species preferred to dine on ammonites. —Riley Black, Smithsonian Magazine, 2 May 2024

Word History

Etymology

Noun (1)

New Latin ammonites, from Latin cornu Ammonis, literally, horn of Ammon

Noun (2)

Late Latin Ammonites, from Hebrew ʽAmmōn Ammon (son of Lot), descendant of Ammon

First Known Use

Noun (1)

1726, in the meaning defined above

Noun (2)

1530, in the meaning defined above

Kids Definition

ammonite

noun

am·​mo·​nite ˈam-ə-ˌnīt 

: any of numerous flat spiral fossil shells of mollusks related to the nautilus that are especially abundant in the Mesozoic era of geological history

ammonitic

ˌam-ə-ˈnit-ik 

adjective