any extinct marine cephalopod mollusc of the order Ammonoidea, which were common in Mesozoic times and generally had a coiled partitioned shell. Their closest modern relative is the pearly nautilus
the shell of any of these animals, commonly occurring as a fossil
an explosive consisting mainly of ammonium nitrate with smaller amounts of other substances, such as TNT
a nitrogenous fertilizer made from animal wastes
1700–10; < New Latin Ammonites < Medieval Latin ( cornū ) Ammōn ( is ) (literally, horn of Ammon ) + -ītes -ite 1; fossil so called from its resemblance to the horn of Jupiter Ammon
First recorded in 1600–10; ammo(nium) + nit(rat)e
An ammonite is an extinct sea creature, a cephalopod distantly related to squids and octopuses. You can also use the word ammonite for the fossilized shells of these ancient animals. The last ammonites died out 66 million years ago, and some ammonite fossils are over 400 million years old. Although their closest living relations don't have hard shells, ammonites did. These ancient mollusks' shells were flat, coiled disks. Their name comes from the creatures' resemblance to a coiled ram's horn: Ammonite is derived from Ammon (or Amun), the name of an Egyptian god who was portrayed wearing ram's horns on his head.
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Ammonite was found in a far-away region of our Solar System where Neptune, the planet farthest from the Sun, has little gravitational influence.
From Space Scoop • Jul. 31, 2025
Recognition for Anning grew after the 2020 release of the film Ammonite, starring Kate Winslet.
From Science Magazine • May 25, 2022
Anning, whose life inspired the feature film Ammonite, was never fully credited for her discoveries due to her gender and social status.
From BBC • May 21, 2022
In Ammonite, this quiet, crushing film, writer-director Francis Lee introduces Mary Anning, a 19th-century palaeontologist whose important fossil finds were appropriated by the male scientific establishment.
From The Guardian • Feb. 21, 2021
“Its Latin name. Ammonite family. You can tell by these close tight ribs it's got, with these extra-fat ones every so often...”
From "Black Swan Green" by David Mitchell
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
