"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 heightened metabolic rates and fur or feather insulation... Perhaps the chief advantage enjoyed by thecodonts centered around their big, slashing attack jaws. These may have made them better big-game hunters, while the more precise cutting teeth of therapsids were more suitable for smaller prey."

“Put a leopard and a together and the former would be in trouble.”

“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.”

“is usually considered a small dinosaur. But the largest individual was an eleven-foot-long animal whose head approached half a yard long, and was of male-timber-wolf mass. If alive today it would be considered a big predator.”

“The biggest living terrestrial predator, the Siberian tiger, at about a third of a metric ton 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.”

“Dinosaurs seem strange, but that is just because we are mammals biased toward assuming the modern fauna is familiar and normal, and past forms are exotic and alien. Consider that elephants are bizarre creatures with their combination of big brains, massive limbs, oversized ears, teeth turned into tusks, and noses elongated into hose-like trunks. Nor were dinosaurs part of an evolutionary progression that was necessary to set the stage for mammals culminating into humans. What dinosaurs do show is a parallel world, one in which mammals were permanently subsidiary, whereas the dinosaurs show what largely diurnal land animals that evolved straight from similarly day-loving ancestors should actually look like. Modern mammals are much more peculiar, having evolved from nocturnal beasts that came into their own only after the entire elimination of nonavian dinosaurs. While dinosaurs dominated the land, small nocturnal mammals were just as abundant and diverse as they are in our modern world. If not for the accident of the later even, dinosaurs would probably still be the global norm.”

“By the Cretaceous crocodilians of essentially modern form were the theropods 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.”