Trilobite fossil. Fossil of the trilobite Delocare rostrata. The trilobites lived from the Lower Cambrian to the Upper Permian period (around 543-248 million years ago). They are an extinct group of marine arthropods with a hard, segmented shell that is divided into 3 sections. Most were bottom dwellers, feeding either on organic sediment on the ocean floor or by catching their own prey. Many could roll themselves into a ball when threatened, thereby ensuring that only the shell was exposed to attackers. Found in Morocco.