Nice, 2.5" Caudillaenus Oblongatus Trilobite - Russia
This large, 2.5" long Caudillaenus oblongatus trilobite from the St. Petersburg region of Russia. This specimen is beautifully preserved and laid out nice and prone. There is some shell restoration on the front of its head on the edge of the tail, but it's pretty minor.
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.