Fossils index


Trilobites were animals that lived in the sea. They are now extinct. Their name is derived from tri and lobos (Greek) meaning three lobes. You can see the three sections in the photo, with the central part running down from the head, and the other two either side.

Kingdom: Animalia
Phylum: Arthropoda
Class: Trilobita
Trilobites were arthropods. Modern arthropods include crabs, insects and woodlice.

The trilobite is the state fossil of Pennsylvania and Wisconsin, USA. Isotelus, a genus of trilobite, is the state fossil of Ohio. Dudley shield

Many trilobites were found in Dudley, West Midlands. They were called Dudley Locusts or Dudley Bugs, and there was a trilobite in the middle of the shield of the former Dudley County Borough Council.

In the Carmarthen area of South Wales, the tails of some trilobites were once thought to be butterflies that had been turned to stone by Merlin. China also has trilobites called Hu-die-shih or stone butterflies. For a different fossil with the same story, see brachiopods.

The Pahvant Ute Indians of western Utah, USA would make trilobite necklaces for protection against evil spirits.

Trilobite Size of trilobite: 22mm

Timescale: Trilobites are very old, from 250 million to over 500 million years old. They disappeared during the Permian-Triassic extinction event, when 90% to 95% of marine species became extinct.

Rolled up trilobite
A trilobite could roll up like a woodlouse. Size: 12mm
A modern woodlouse
Woodlouse rolled up
Woodlouse rolled up

The head of the trilobite, with eyes either side

The trilobite tail tucked under its head

From the side, head and eye on the left

Another rolled up trilobite Size: 18mm

Side view, head bottom left

And another rolled trilobite, from Morocco. Size: 20mm

The head is at the top, tail curled up underneath.


A trilobite has a head, or cephalon, a thorax and a tail. You can see them in this complete trilobite.

The part of the trilobite that gets fossilised is the exoskeleton. The trilobite would moult its exoskeleton several times during its life. So many fossils are of the moult rather than the dead animal. The moult would often break up the exoskeleton, so you can get only part of the trilobite. In this photo, you can see a trilobite tail on top of a complete trilobite. Size of complete trilobite: 26mm

The other side of this rock was yet another trilobite (see photo at the top of this page). The fossil came from Cambrian-Wheeler Shale in Utah, USA.

The fossil below is made of a different mineral, as you can tell from the colour. Size: 60mm