1. an extinct marine mollusk with a flat spiral shell, found as fossils
Usage: paleontology

Examples

• The museum displayed a large ammonite fossil from the Jurassic period.
• Collectors often search beaches for ammonite specimens.
• The ammonite’s spiral shell made it easy to identify among other fossils.
• Scientists study ammonites to understand ancient ocean environments.
• The limestone contained several well-preserved ammonite impressions.
• Ammonites were abundant in prehistoric seas but became extinct with the dinosaurs.