A new discovery was found last year on Tyrannosaurs Rexes. It was introduced that T-Rexes are not their own species, and that there are three species: Tyrannosaurs Imperator, Tyrannosaurs Regina, and Tyrannosaurs Rex. The difference between the three species is the layers in where they were found, the femur bone, and the amount of incisor teeth. The scientists organize the groups on the thickness of the femur. Another form of identification is examining how many incisor teeth the specimens have. A Tyrannosaurs Imperator has two incisor teeth and has a robust femur, while a Tyrannosaurs Regina has one incisor tooth and slim femurs. The Tyrannosaurs Rex has one incisor tooth and robust femurs. Right now, there is a debate on whether there should be the three species or if they should be kept as one.