Unlike ammonites, some nautiloids are still alive today.
Nautiloids are the only cephalopods with an external shell that are still alive today. The living animal, Nautilus, is housed in a coiled shell, exposing only its head and tentacles to the outside world. Much of the shell is divided into chambers that are filled with gas. By adjusting the levels of gas the animal may live in the depths of the ocean and move to shallow water at night time to feed.
Shell of recent nautiloid cut in half to show inner chambers.
Nautiloids first appeared about 500 million years ago. Then, there were many different species and they lived in the seas throughout the world. Today, the few surviving species are found in seas around Australia and the Philippines. They are often referred to as living fossils, as they have changed very little over millions of years.
A fossil nautiloid which has been cut in half to show its inner chambers.
The molluscs are split into different groups - the gastropods, bivalves and cephalopods. The cephalopods are also split into three groups.
If you read these pages you should become an expert invertebrate identifier!
The major groups are listed below - select a link to learn more about this type of fossil.
Echinoderms Return to the wheel
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