Take a trip back in time five hundred million years ago to explore the underwater depths dominated by ancient sea monsters. Uncover the mysteries of the aquatic reptiles lurking below sea-level as they develop long and sharp teeth, massive tails, and unparalleled strength! These features allowed them to defeat all that was in their path and become the unchallenged hegemons of the ocean. Read about the evolution of sea monsters across the Triassic, Jurassic, and Cretaceous periods as each one takes control of its own destiny. Age of Ancient Sea Monsters tells the story of how these courageous ocean creatures adapted to new environments and worked for their survival. This third volume from the PNSO Field Guide to the Ancient World will inspire paleontology enthusiasts everywhere to explore their nearby lakes, ponds, and oceans!