The Cretaceous period lasted approximately 79 million years, and ended with a major extinction event about 66 million years ago.
A newly described Cretaceous dinosaur had puny arms like Tyrannosaurus rex, though the two species were not closely related.
The first Gorgosaurus to be auctioned may go for as much as $8 million. But scientists are dismayed.
The researchers say their findings defy stereotypes of dinosaurs only thriving in warm, humid environments.
A hefty abelisaurid is the fourth large, predatory dinosaur discovered in Egypt's Bahariya Formation, alongside other sizable Cretaceous carnivores.
An herbivorous dinosaur used its vicious-looking claws to forage for plants near the shores of Cretaceous seas.
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