Ammonites

Ammonites were shelled cephalopods that first appeared about 450 million years ago. The cephalopod group can be divided into three subgroups, all of which you can find at Geoneiro: ammonites, coleoids (such as squid and octopuses), and nautiloids. Ammonites are a very important guide to date the geologic layers of our world, because of their exceptional dissemination in  sedimentary rock.

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Ammonites, the ocean-dwelling molluscs from millions of years ago, had a chambered shell that they used for buoyancy. They were born with small shells and, when they grew, they built new chambers. The ammonites would move their body into a new chamber and seal off their old  chambers with walls known as septa. It is rare to find these ammonites which still show septa; many hours of work go into the painstaking preparation that eventually creates this special kind of insight into the life and growth of the ammonite. Ammonites died out around 66 million years ago, during a mass extinction event, but at Geoneiro we  still admire their existence.