dinosaurs deceived us

Taken together, the "loss" of four species from the Hell Creek formation reveals that the dinosaurs that lived there up until 65 million years ago were not as diverse as previously thought. Triceratops and torosaurus have long been regarded as the last survivors of the horned dinosaurs, a large group that appeared in the Jurassic and reached its heyday about 80 million years ago. Now it seems that only one species made it through to the end of the Cretaceous. This could be evidence to support a disputed theory that dinosaur diversity was in decline long before an asteroid impact wiped them out.