By the Cretaceous crocodilians of essentially modern form were the theropods [sic] main competitors. Yet crocodilians appear to be less abundant in m… - Gregory S. Paul

Dinosaur remains have been found by humans for millennia and probably helped form the basis for belief in mythical beasts including dragons.

The biggest living terrestrial predator, the Siberian tiger, at about a third of a metric ton (300 kg) pales in comparison to the biggest of the meat-eating dinosaurs, which reached 5 to perhaps 20 metric tons - the size of elephants and bigger. But while elephants cannot run, the biggest predatory dinosaurs probably ran as fast as horses, and they hunted herbivores that themselves were as big as or bigger than elephants.

When it was assumed that birds did not evolve from dinosaurs, it was correspondingly presumed that their flight evolved among climbers that first glided and then developed powered flight. This has the advantage that we know that arboreal animals can evolve powered flight with the aid of gravity, as per bats. When it was realized that birds descended from deinonychosaurs, many researchers switched to the hypothesis that running dinosaurs learned to fly from the ground up. This has the disadvantage that it is not certain whether it is practical for tetrapod flight to evolve among ground runners working against gravity.
The characteristics of birds indicate that they evolved from dinosaurs that had first evolved as bipedal runners, and then evolved into long armed climbers. If the ancestors of birds had been entirely arboreal, then they should be semiquadrupedal forms whose sprawling legs were integrated into the main airfoil, like bats. That birds are bipeds whose erect legs are separate from the wings indicates that their ancestors evolved to run.