Image by: British Geological Survey
Trilobites
What was it?
A sea creature that became extinct 250 million years ago; long before the dinosaurs. They are arthropods – the same group of animals as spiders, insects and crabs. They have a hard external skeleton that is articulated – so they can roll up to protect their softer under parts – just like wood lice.
How old is it?
The trilobites found in Northumberland rocks are Carboniferous and around 325 million years old. But some trilobites found in Wales and Scotland are almost 600 million years old. They are a really useful fossil for geologists because we can trace their evolution over millions of years and also because we can use different species to understand how the world looked back then – for instance that Scotland was much closer to North America and separated by a big ocean from England!
Where did it live?
The trilobites found in Northumberland appear to have lived in shallow seas along with corals and other reef animals. But they have also been found in very deep oceans.
Where are the fossils found?
They are not easy to find but their shell fragments can be found in limestone rocks along the coast, for example just south of Cullernose Point. They are usually associated with other sea creature fossils like crinoids and brachiopods.
Are these animals still alive today?
No, despite a lot of searching no modern relative of the trilobite has been found living today, although the closest relative is the horseshoe crab.