This is large, spiny Leonaspis trilobite from Ofaten, Morocco.The genal spines have been prepared totally free of the surrounding rock and it has wonderful shell detail including many small nodes on the axis, a feature often last on specimens with lesser quality preparation.
Trilobites were a very diverse group of extinct marine arthropods. They first appeared in the fossil record in the Early Cambrian (521 million years ago) and went extinct during the Permian mass extinction (250 million years ago). They were one of the most successful of the early animals on our planet with over 25k described species, filling nearly every evolutionary niche. Due in large part to a hard exoskeleton (shell), they left a excellent fossil record.