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

Ever since the early '80s I have applied feathers to many of the small dinosaurs, and never did smaller theropods without them. I did so because birds evolved from small theropods, and the evidence for the latter having the high metabolic rates that would have promoted the evolution of insulation was solid. I used to receive endless grief for this. The counter-argument was that no feathers had been found on any dinosaurs, and scales had, so I was engaging in unfounded speculation. But these points were actually not scientific. Scales had been discovered only on large dinosaurs, so illustrating small ones with scales was no less speculative than putting feathers on them. It would be like illustrating little mammals with naked skin if all we had was elephants and rhinos to base mammal integument on. I knew that my thesis was logical, so I bided my time.

How would we think and feel about predatory dinosaurs if they were alive today? Humans have long felt antipathy toward carnivores, our competitors for scarce protein. But our feelings are somewhat mollified by the attractive qualities we see in them. For all their size and power, lions remind us of the little creatures that we like to have curl up in our laps and purr as we stroke them. Likewise, noble wolves recall our canine pets. Cats and dogs make good companions because they are intelligent and responsive to our commands, and their supple bodies make them pleasing to touch and play with. And, very importantly, they are house-trainable. Their forward-facing eyes remind us of ourselves. However, even small predaceous dinosaurs would have had no such advantage. None were brainy enough to be companionable or house-trainable; in fact, they would always be a danger to their owners. Their stiff, perhaps feathery bodies were not what one would care to have sleep at the foot of the bed. The reptilian-faced giants that were the big predatory dinosaurs would truly be horrible and terrifying. We might admire their size and power, much as many are fascinated with war and its machines, but we would not like them. Their images in literature and music would be demonic and powerful - monsters to be feared and destroyed, yet emulated at the same time.

By the Cretaceous crocodilians of essentially modern form were the theropods [sic] main competitors. Yet crocodilians appear to be less abundant in most Mesozoic deposits than they are later in the mammal-dominated Cenozoic. Not only that, but they tended to be small-bodied: few specimens were as big as American alligators or Nile crocodiles. It is possible that theropods were eating the crocs. Even today, big cats once in a while kill a fairly large crocodilian. A tyrannosaur could have swallowed one whole, and gone into the water after them. Constant attacks could have suppressed croc populations, and favored the smaller, harder to catch species.