Mental Floss has a post about trilobites. Trilobites were arthropods. they existed on earth from the lower Cambrian to the Permian mass extinction, that's about 300 million years. Over 20,000 species have been described. And more new ones are added to the list every year. Ohio (Isotelus), Wisconsin (Calymene celebra), and Pennsylvannia (Phacops rana) have trilobites designated as their state fossil.
They are one of the most common favorites and are collected by many. If you go to the right place, you can collect them yourself... For more information visit www.trilobites.info.
