Ammonite

Ammonoidea

A coiled shell from a fast-evolving group of ancient ocean animals.

Cretaceous Madagascar

Sample content • provenance shown broadly for demonstration

At a glance

Fast Facts

110 million years old

Cretaceous Period

Marine cephalopod

Madagascar

Read the evidence

The Story

Ammonites were relatives of modern squid and octopuses. Their chambered shells helped them control buoyancy as they moved through prehistoric seas. Because species changed quickly, geologists use their fossils to compare the ages of distant rock layers.

Stefan's field note

The ammonite is one of my favourites because it looks almost like it was designed, but animals were making these spiral shells more than 100 million years ago.

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Where Does It Fit?

4.6 billion years ago

Today

Cretaceous Period

Warm shallow sea • Body fossil

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