This would be a headshot of Stegosaurus ungulatus, from the Late Jurassic of North America. I have seen it recently suggested that, unlike most ornithischian dinosaurs, stegosaurs would have sported a keratinous beak only on their lower jaw, with the tip of the upper jaw being covered in skin. It looks a little weird to me, but that’s going to be the case with almost any revision of an iconic dinosaur’s appearance.