Trilobite (Huntoniatonia lingulifer)

Devonian, 415 million years old, Clarita, Oklahoma, USA

Thousands of trilobite genera have been described so far from all Paleozoic seas. After their heyday during the early Paleozoic Era, the Devonian marked the start of a long downfall. The last trilobites became extinct around 250 million years ago, at the time of the Permian–Triassic extinction event.