Despite the film's title, the Tyrannosaurus reconstruction used to promote the program was deeply inaccurate. The reconstruction was based on the fossil specimen nicknamed Tristan, which suffered many deformities during the fossilization process, such as an extreme overbite and teeth slipping out of their sockets. The program's T. rex took the misshapen skeleton's proportions and applied them to a live reconstruction, resulting in a deformed Tyrannosaurus. This error was corrected for the film itself, in which the animal is shown with normal proportions.