Tyrannosaurus rex arose during the Cretaceous period about 85 million years ago and thrived as a top land predator until the dinosaurs went extinct 20 million years later. This skeleton, on display in Chicago's Field Museum, is a cast of perhaps the world's most famous fossil: "Sue," a 67-million-year-old T. rex discovered in 1990 in South Dakota by field paleontologist Sue Hendrickson. It is the most complete, best preserved, and, at 42 feet (12.8 meters), the largest T. rex specimen ever found.
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See photo of dinosaurs and other plant and animal life from the Cretaceous period from National Geographic.