Ammonite
/ˈæmənaɪt/
Definition 1 of 2
Pro Tip 1/3Prehistoric Existence
Ammonites lived millions of years ago, so the term highlights ancient history and geology. 
The rock layer containing the ammonite must be Jurassic in age.
Pro Tip 2/3Extinction Event
Ammonites became extinct, which often links to discussions on natural history and mass extinctions. 
Like the dinosaurs, the ammonite vanished during a mass extinction.
Pro Tip 3/3Fossil Identification
Ammonites are commonly found as fossils, so 'ammonite' refers to both the creature and its fossil. 
That spiral pattern is the hallmark of an ammonite's fossil.