Conceptual illustration of the dinosaur Tyrannosaurus rex fighting an Ankylosaur during the Cretaceous Period. T-rex was a huge carnivore and primarily ate herbivorous dinosaurs, including Ankylosaur. Tyrannosaurus rex was may not have been a lone operator and hunted in packs. Ankylosaurus was built like a living tank, with extremely thick, bony plates of armour on its body, even including armoured eyelids. Its tail also had a second function, it could act as a deadly club.