Dinosaurs & Prehistory - Fossils & Earth history - Ammonites - Fossils - Deep time
What were ammonites?
Correct!
Ammonites were extinct marine cephalopods, relatives of squid and nautiluses. Their shells were often coiled in a spiral and are well known as fossils.
Because many ammonite species lived only during particular intervals of Earth's history, their fossils often help date rock layers.
Source: National Park Service
