Trilobite (Phacops rana) was designated the state fossil of Pennsylvania in 1988. An elementary school science class campaigned for this prehistoric invertebrate that lived in Pennsylvania more than 250 million years ago. All State Fossils Pennsylvania's state fossil can be recognized by its large, frog-like eyes ("rana" is a reference to a common frog), its fairly large size (up to 6 inches long), and its habit of rolling up into a ball like a pill bug.
