Anatotitan (Giant Duck) was a large Hadrosaurid Dinosaur. It was 12-13 metres long, and was essentially a smaller, but similar version of the 11-12 metre long Edmontosaurus it was very closely related to (recent studies show they might be the same) have been similar to Edmontosaurus in many ways, though most recognise the two as distinct species, through comparative anatomy. Edmontosaurus, its close cousin, lived at the same time and throughout North America. Anatotitan would have had almost an identifical mode of life, grazing on a variety of vegetation. These animals had batteries of teeth, for processing the vegetation, in a grinding motion similar to chewing. It was one of the most obvious 'duck-billed' Dinosaurs, with such a flat skull. Like Edmontosaurus, it would have been preyed upon by Tyrannosaurus rex. Healed tooth marks are known from Edmontosaurus, and Parasaurolophus, showing predation by the Tyrannosaurs. Anatotitan must have also been attacked, as they were contemporaneous with Tyrannosaurus rex. Even so, Anatotitan was much more dangerous than any Edmontosaurus, and old bull males could have been a possible match for an unwary Tyrannosaurus rex. They could have struck with their tails, and trampled with their feet. Perhaps old males were heavily agressive, defending hareems of females, and thus even against a Tyrannosaur they may have fought back, as tough bulky, 5-6 ton beasts that could trample a predator to death. We should not overlook the fact that compared to modern animals, these so called lightweights, were actually incredibly powerful and unwittingy danger beasts. Even a Tyrannosaur would need caution when attacking a large individual. Nowadays Anatotitan is now Edmontosaurus annectans.