What gave archosaurs the edge as large predators at this time, and therapsids the edge as smaller ones? Frankly, I am not sure. Both seem to have had… - Gregory S. Paul

This is the theropod. Indeed, excepting perhaps Brontosaurus, this is the public's favourite dinosaur, having fought King Kong for the forced favor of Fay Wray and smashed Tokyo (with inferior special effects) in the guise of Godzilla.

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.

If not for the long tail, one might mistake a theropod for a big, toothy, marauding bird in the dark. That theropods are birdlike is logical, since birds are their closest living relatives. Remember that next time you eat a drumstick or scramble some eggs.