Newly found species explains how T. rex became king of dinosaurs (5)

Photo taken on March 14, 2016 at Smithsonian National Museum of Natural History shows fossils of claw and teeth of dinosaurs in Washington D.C., the United States. Scientists said Monday they have discovered the fossilized remains of a new horse-sized dinosaur that revealed how Tyrannosaurus rex (T. rex) became one of Earth's top predators about 70 to 80 million years ago. (Xinhua/Yin Bogu)