Triceratops drinking at a pond, artwork. This was a common dinosaur in the late Cretaceous period, from around 70 million years ago until the extinction of the dinosaurs some 65 million years ago. Triceratops was a herbivorous dinosaur that could reach a length of up to nine metres. It may have used its horns and its neck shield to defend itself against attack, but it is now thought that they are more likely to have been used in courtship and dominance displays.