Cretaceous / dinosaur.A Tyrannosaurus Rex (Tyrannosaurus) in its natural environment 67 million years ago.(Tyrannosaurus; an extinct genus of theropod dinosaurs that belong to the genus of tyrannosaurids and lived in western North America during the late Maastrichtian at the end of the Cretaceous approximately 68 to 66 million years ago. Tyrannosaurus rex; whose name etymologically means "King of the tyrannous lizards"; is one of the most well-known species of dinosaur and was one of the last non-avian dinosaurs to exist until the Cretaceous Tertiary mass extinction 66 million years ago).3D illustration; 2019.