Triceratops horridus skeleton. Triceratops is an extinct genus of herbivorous ceratopsid dinosaur that lived during the late Maastrichtian stage of the Late Cretaceous Period, around 68 to 65 million years ago in what is now North America. It was one of the last dinosaur genera to appear before the great Cretaceous-Tertiary extinction event. Bearing a large bony frill and three horns on its large four-legged body, Triceratops is one of the most recognizable of all dinosaurs. A complete Triceratops skeleton has yet to be found since the introduction of the genus in 1887. The function of their frills and three distinctive facial horns has long inspired debate. Although traditionally viewed as defensive weapons against predators, the latest theories claim that it is more probable that these features were used in courtship and dominance displays, much like the antlers and horns of modern ungulates. Royal Tyrrell Museum, Alberta, Canada.