How to recognise them

Only known from boreholes - not in outcrop at the surface.

Fossil Info

Limnestheria are tiny crustaceans called spinicaudata or clam shrimps that lived in the Carboniferous Period around 330 million years ago (although clam shrimps evolved in the Devonian Period or a little earlier). They have two valves so look very like mussels - but they have jointed limbs and body plus antennae, so they are definitely arthropods! These little fossils are only about 1 cm across and have relatives in the clam shrimp family that are still alive today. Their legs are constantly moving and catch floating food particles and move it to the mouth. 

Fun Fact

These tiny fossil crustaceans are remarkably well preserved - even their legs and anntenae have survived fossilisation.