Tyrannosaurus Rex One of the most ferocious dinosaurs was T.rex. It lived in Montana 66 million years ago. The environment back then was swampy with lots of forests and was coastal. T.rex didn't roar. In fact, it made a croaking sound. Here is a video: As the video shows, T.rex didn't really make a loud sound. Jurassic Park's T.rex sound was made by combining an elephant, a tiger, and a lot of different animals. You can use a lot of animal sounds (ex. a crocodile, a panther, a puma, a jaguar, a leopard, a lion) to make a T.rex roar. Jurassic Park's T.rex is also inaccurate because it has wrinkly, naked skin instead of feathers. Here is another video that explains that: Finally, to conclude T.rex was about 42 feet long, about 20 feet tall, and about 6 tons.