The dinosaurs are not extinct. The colorful and successful diversity of the living birds is a continuing expression of basic dinosaur biology. - Robert T. Bakker

No one, either in the nineteenth century or the twentieth, has ever built a persuasive case proving that dinosaurs as a whole were more like reptilian crocodiles than warm-blooded birds. No one has done this because it can't be done.

Plants and plant-eaters co-evolved. And plants aren't the passive partners in the chain of terrestrial life. Hence today's Pop Ecology movement is quite wrong in believing that plants are happy to fill their role as fodder for herbivores in a harmonious and perfectly balanced ecosystem. A birch tree doesn't feel cosmic fulfillment when a moose munches its leaves; the tree species, in fact, evolves to fight the moose, to keep the animal's munching lips away from vulnerable young leaves and twigs. In the final analysis, the merciless hand of natural selection will favor the birch genes that make the tree less and less palatable to the moose in generation after generation. No plant species could survive for long by offering itself as unprotected fodder.

Without doubt the most dangerous devices for active defense among the Dinosauria emerged in Triceratops. The scene has been portrayed in paintings, drawings, and illustrations hundreds of times, but it remains thrilling. Tyrannosaurus, the greatest dinosaur toreador, confronts Triceratops, the greatest set of dinosaur horns. No matchup between predator and prey has ever been more dramatic. It's somehow fitting that those two massive antagonists lived out their co-evolutionary belligerence through the very last days of the very last epoch in the Age of Dinosaurs. Tyrannosaurus stood over twenty feet tall when fully erect, and a large adult was as heavy as a small elephant - five tons. No predatory dinosaur, no predatory land animal of any sort, had more powerful jaws. Withstanding a Tyrannosaurus's attack required either tanklike armor – the approach taken by Ankylosaurus – or most powerful defensive weapons - the approach taken by Triceratops.