During the final 20 million years of the Cretaceous, tyrannosaurs flourished, ruling the river valleys, lakeshores, floodplains, forests, and deserts of North America and Asia. There is no mistaking their signature look: huge head, athletic body, sad arms, muscular legs, long tail. They bit so hard that they crunched through the bones of their prey; they grew so fast that they put on about five pounds every day during their teenage years; and they lived so hard that we have yet to find an individual that was more than thirty years old when it died. And they were impressively diverse: we have
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