Creature from the Cambrian Period (IMAGE) University of Chicago Caption A species of trilobites found in Nevada. Trilobites went extinct 250 million years ago, long before the appearance of the first dinosaurs. Credit Photo by Dan Dry Usage Restrictions This image may be used to illustrate news reports about the findings described in this announcement. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.