This is a natural association of a Crotalocephalina gibbus and enrolled Reedops from Foum Zguid, Morocco. The specimens has been painstakingly prepared to remove the surrounding limestone, leaving the trilobite fossils
perched in an aesthetic display. Nearly all of the rock has been removed from underneath the 2.6" long Crotalocephalina, a very time consuming task.
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.