The story of Triceratops starts with a pair of horns. In 1887, Othniel Charles Marsh's first find was a pair of Triceratops horn cores, the bony inner part of the horns. At first, Marsh thought the horn bones belonged to a giant bison. In 1889 he named the animal Triceratops. The name means "three-horned face." The skull he used to name it belongs to Yale's Peabody Museum of Natural History. John Bell Hatcher found and dug up more than 30 Triceratops skulls for Yale in two years.

Hundreds of Triceratops skulls have been found in Montana and the Dakotas. Usually they were found without the rest of the skeleton. Many fossils have come from Montana's Hell Creek rocks. Triceratops is one of the most common dinosaurs found as fossils. Its skull was one of the largest of any land animal. An adult skull was often at least 6 feet long. In 1905, the Smithsonian mounted the first Triceratops skeleton. It was put together from 10 specimens from various places in Niobrara County.

Skin impressions found with Triceratops fossils show how it looked. Triceratops had large, pebbled scales. You may have heard that Triceratops was related to rhinoceroses. In fact, Triceratops was a dinosaur and was not related to rhinoceroses, which are mammals. One fossil even tells of danger. It has a horn that was bitten off, with bite marks that match Tyrannosaurus. The horn healed, so at least some Triceratops survived such an attack.

In 1997, an amateur fossil hunter found a baby Triceratops skull in Montana's Hell Creek Formation. The baby skull studied at UC Berkeley likely came from a year-old animal about three feet long. As of 2017, a baby frill bone found in the field was only the fourth specimen of its kind ever found. In August 2017, a construction crew in Thornton, Colorado, found a Triceratops.

Fossils also show the world a dinosaur lived in. Triceratops lived in North America about 68 to 66 million years ago. Tyrannosaurus rex lived at the same time and place. In what is now Colorado, the Late Cretaceous was warmer and more humid than today. It had palms, other flowering plants and ferns. Scientists think Triceratops died out with all the other non-bird dinosaurs. They think it happened after an asteroid hit near Mexico.

Words to know

• specimens: fossil samples
• scales: skin plates
• impressions: pressed marks
• humid: damp
• Cretaceous: dinosaur age