Mesozoic that would move into their current positions during the next era. The climate of the Mesozoic was varied, alternating between warming and cooling periods. Overall, however, the Earth was hotter than it is today. Dinosaurs appeared in the Late Triassic and became the dominant terrestrial vertebrates early in the Jurassic, occupying this position for about 135 million years until their demise at the end of the Cretaceous. Birds first appeared in the Jurassic, having evolved from a branch of theropod dinosaurs. The first mammals also appeared during the Mesozoic, but would remain small—less than 15 kg (33 lb)—until the Cenozoic.
T-Rex: Back to the Cretaceous continued for two weeks on location in Dinosaur Provincial Park. Yet the filmmakers faced a challenge in finding a realistic environment to set the live-action filming portion for the Cretaceous period sequences when Ally finds herself wandering amidst the lush vegetation of 66 million years ago. The location used to film Cretaceous period scenes in the end was in the Olympia rain forest in upper Washington state. The special considerations that must be made when working with IMAX 3D presentation also made it crucial that the background features of the shooting locations were ideal. Besides shooting locations, extensive computer-generated imagery