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Echinoderms

We can all recognise an echinoderm.

Echinoderms are a group of animals that include starfish, sea-urchins and sea-lilies (or crinoids). They don't have muscles, but move instead using pressurised water that they pump through special tubes to expand and contract different parts of their body. Although they are strange creatures in lots of ways, they are actually more closely related to humans than most other invertebrates.

Fossil starfish Fossil sea urchin
A fossil starfish and sea urchin.

Echinoderms live in many different ways, but most crawl around on the sea-floor looking for food. Sea-lilies, however, are stationary, and are attached to the sea-floor with a long stem. At the end of the stem is their body, from which lots of arms wave around to catch food that floats past.

Fossil echinoderms are quite easy to spot, as they are made of chunky plates of a mineral called calcium carbonate. Most also have an obvious five-way symmetry - for example most starfish have five arms.

Fossil sealily Fossil brittlestar
A fossil sea-lily and brittle star.

A fossilised crinoid bed Echinoderms first appeared around 540 million years ago. They are found as fossils in rocks of all ages, and are still common in oceans across the world. Whole echinoderm fossils are quite rare, but are amongst the most beautiful of fossils.

Echinoderms, like these sea-lilies, can be beautiful fossils

 

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.

Sponges Corals
Molluscs Brachiopods
Arthropods Graptolites
Echinoderms Return to the wheel

If you know it all already, return to the Homepage or test yourself with our Quiz!