Toward the end of the Age of Dinosaurs, during a time known as the Late Cretaceous, a new type of giant predator appeared along the southern coasts of North America. It was a huge species of crocodylian and is called Deinosuchus. Neither a crocodile nor an alligator, it was an ancestor of both modern groups, but it reached weights of many tons and it had some features unique to the species. Average-sized individuals were bigger than the carnivorous dinosaurs with which they cohabited; the largest specimens were the size of a T-rex. This book is the biography of these giant beasts, including the long history of their discovery, new research about their makeup, and the first published evidence about their prey. Generations of people have stared at the 6-foot reconstructed skull at the American Museum of Natural History in New York, not realising that the only real bones in the specimen were bits of snout and lower jaw. New fossils and research show that the actual animal was quite different from the reconstruction, and now we can reliably assemble the skull and the remainder of the animal. The book also deals with the ancient life and geology of the coastal areas where Deinosuchus thrived, including its competitors and its prey, which likely included carnivorous dinosaurs among its numbers. Since Deinosuchus is found on eastern and western sides of the Great Inland Sea that split North America, it must have crossed this vast seaway during the Late Cretaceous. How and why the crocodylian crossed the seaway is the focus of a key chapter in the book. There is also detailed discussion of the methods used to determine the size of these giant animals, how we can date the fossils and describe their living environments, and why we can be sure who at whom 80 million years ago.