5.75" Ordovician Trilobite (Megistaspis) - Fezouata Formation
This is a nice, 5.75" long Megistaspis hammondi trilobite from Fezouata Formation of Morocco. This asaphid trilobite could reach enormous sizes, but most examples you see out of Morocco are heavily restored or entirely fake. This one is much better preserved than most specimens. There is only about 2-3% shell restoration along repaired cracks.
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.