A 'trilobite Pompeii': Perfectly preserved fossils of ancient sea critters found buried in volcanic ash

If you've ever visited the fossil gallery of a natural history museum—or its gift shop, for that matter—you've probably seen the armored body remains (or exoskeletons) of an extinct group of animals called trilobites. These ancient marine arthropods lived in the world's oceans from 521 million to 252 million years ago.