6. Chasmosaurus
We’ve had a lot of strange herbivores this article. It’s amazing that more ceratopsians aren’t on this list. Triceratops is nice, but the moment you get into things like Styracosaurus and Pachyrhinosaurus, you realize how crazy herbivore head frills can get. Bear in mind that we still don’t really know what any of these were used for; the horns could be defensive, a signal to others of the species, used to attract mates or some combination of the above. Some ceratopsian skulls would make only questionably good shields.
Chasmosaurus falls squarely into the “what was this frill for?” category. It was first found in Canada and was from the Late Cretaceous. The dinosaur is so named for the giant openings (“chasms”) in its frill. This frill doesn’t offer much protection, so what was it for? Was Chasmosaurus much faster than its sturdier brethren, thus warranting a lighter frill? The best theories so far are mating displays and thermoregulation. The defense was definitely not this three-horns strong suit, so those are as good of guesses as any.