Chasmosaurus was a medium sized ceratopsian from North America. This animal reached an adult size of around 16 feet in length and weighed a little over 1 ton. It had 3, somewhat short, horns on it's head. The frill of Chasmosaurus however was quite large compared to its overall body size. Chasmosaurus is known from pretty good remains, so it's a relatively well understood dinosaur. Chasmosaurus roamed the Earth about 70-75 million years ago.