Some of the most commonly found fossils belong to extinct sea creatures! Many fossils of extinct trilobites and ammonites have been found in places around the world. These Paleozoic-era Sea creatures allow scientists to discover a world before the most famous dinosaurs roamed. Through this book's investigation into the fossils of sea creatures, readers will learn how scientists interpret these early fossils. With photographs of the different fossils, readers will discover different sea creatures and learn what researchers believe the world may have looked like when they were alive.