Non-avian dinosaurs are a group of reptiles that dominated terrestrial ecosystems during the Mesozoic Era, specifically from the late Triassic to the end of the Cretaceous period, around 66 million years ago. These creatures, which include well-known species like Tyrannosaurus rex and Triceratops, went extinct during a mass extinction event at the close of the Cretaceous. Their extinction marked a significant turning point in Earth's biological history, paving the way for the rise of mammals and ultimately, birds as the only surviving lineage of dinosaurs.
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