Another bias also works against herbivorous dinosaurs, however. (dinosaur factory)Paleobotanists are a bit chauvinistic about their objects of study. They tend to regard plants as the movers and shakers in evolution, and the plant-eaters are consigned to the role of reactors and followers. As one paleobotanist expressed it, “The sun gives energy to plants, and plants give energy to the animals. Therefore, the plants evolve and the animals must coevolve.” Stated thus, the assertion is understandable, but it’s misleading. Co-evolution works both ways.
When plant-eating dinosaurs evolved more effective teeth or fermenting chambers, the plant species had to adjust to the new weaponry or die. Whichever evolved faster, plant or animal, had the evolutionary initiative. (life size dinosaur)And plant-eating dinosaurs evolved fast, faster than the plants. On average, a species of dinosaur endured two or three million years before becoming extinct and being replaced by a new species. That’s a brisk rate of evolutionary turnover, as fast as the mammals’.
Such rapid replacement of old adaptive models by new ones guaranteed that the dinosaur plant-eaters were always coming up with novel ways to bite, chew, ferment, and digest plant tissue. (animatronic dinosaur)Mesozoic plants, on the other hand, usually evolved more slowly—the average species of plant lasted eight million years before being replaced by a new one. Since the turnover wasn’t as fast, the plants must have been lagging behind the dinosaurs in the evolutionary race.
Herbivorous dinosaurs in fact were the fastest-evolving part of the entire Mesozoic land ecosystem, even faster at adaptive remodeling than their meat-eating relatives. (animatronic dinosaur costume)Tyrannosaurus rex, the fifty-foot-long Cretaceous killer with seven-inch teeth, was really just a sophisticated variation on the basic predator plan first evolved a hundred million years earlier in the Late Triassic. Bone by bone, Tyrannosaurus rex was fundamentally little different from its an cient Triassic ancestors. But the Cretaceous plant-eaters—three-horned Triceratops, club-tailed Ankylosaurus, broad-beaked Edmon-tosaurus—carried skull and jaw developments totally unknown in the Triassic.