Large herds of herbivorous ornithischians also thrived during the Cretaceous, such as Iguanodon (a genus that includes duck-billed dinosaurs, also known as hadrosaurs), Ankylosaurus and the ceratopsians. Theropods, including Tyrannosaurus rex, continued as apex predators until the end of the Cretaceous.

tyrannosaurs were the killing machines of the late Cretaceous period. These huge, powerful carnivores were all legs, trunk, and teeth, and they preyed relentlessly on smaller, herbivorous Dinosaurs (not to mention other theropods