five-horned herbivorous dinosaur found as fossils in North America and possibly eastern Asia dating from the Late Cretaceous Period (99 million to 65 million years ago). Pentaceratops was about 6 metres (20 feet) long and had one horn on its snout, one above each eye, and one on each side of the large bony neck frill. It was a ceratopsian related to the more familiar Triceratops and is especially well known from the Kirtland Shale of New Mexico, U.S.