Saurolophus is a large hadrosaurid that lived in Asia and North America during Late Cretaceous (Campanian) times, about 74 to 70 million years ago. Like many hadrosaurs, Saurolophus has a distinctive crest, which in its case slopes upward from the back of the skull. The holotype skeleton (displayed in the AMNH) measures 8.4 meters long.