Triceratops had two long horns above its eyes and one short horn on its nose, and the horns and skull bones were covered in keratin, the material in fingernails. Scientists think Triceratops used these horns to fight other Triceratops. A 2009 study found frill bones injured about 10 times more often in Triceratops than in Centrosaurus, another horned dinosaur. You may have heard that Triceratops fought mainly with Tyrannosaurus, which lived at the same time and place. It may also have used its horns against predators such as Tyrannosaurus.
Did Triceratops live alone or in groups? Triceratops fossils are usually found one at a time, which suggests many lived alone. Hundreds of Triceratops skulls have been found in Montana and the Dakotas, but usually without the rest of the skeleton. But there is also evidence for the other idea. A 66-million-year-old Montana site holds at least three young Triceratops buried by one flood. That suggests they were probably living together. Ceratopsians, the group of horned dinosaurs, probably traveled in herds. Bone beds in the western United States hold the bones of hundreds of individuals of one species.
Teeth show how Triceratops fed. It had a beak like a bird's, and it probably ate low-growing plants. Rows of teeth in the back of its jaws cut up tough plants. The teeth grew tightly together in rows called a dental battery. Each tooth had five layers of tissue, more than the four in the teeth of horses and other hoofed mammals. Most reptile teeth are used for grabbing and crushing and do not meet like mammal teeth, so reptiles cannot really chew. Triceratops was a plant-eater, and its rows of teeth are what cut up its tough food.
How many kinds of Triceratops were there? By 1949, as many as 16 species had been named, because nearly every difference between skulls was treated as grounds for a new species. Scientists today count two, T. horridus and T. prorsus. T. horridus had a smaller nose horn and a longer beak. T. prorsus had a longer nose horn and a shorter beak. A 2014 study placed more than 50 Triceratops skulls in the rock layers of Hell Creek, Montana, to see how the animal changed over time. Over roughly one to two million years at the end of the Cretaceous, Triceratops changed from a small nose horn and long beak to a long nose horn and shorter beak.
Some skulls have a story of their own. In 1887, Othniel Charles Marsh's first find was a pair of Triceratops horn cores, the bony inner part of the horns. He first thought the horn bones belonged to a giant bison, and he named Triceratops in 1889. A Triceratops skull was collected in 1891 on a Yale expedition in the Lance Formation of Wyoming, led by John Bell Hatcher. The skull Marsh used to name Triceratops belongs to Yale's Peabody Museum of Natural History. Not every skull had a safe trip. A Yale Triceratops skull sent to the Netherlands was apparently dropped on arrival and smashed into hundreds of pieces.
The head of Triceratops also changed with age. The horns and frill were already there in a baby skull, not just in adults, and baby Triceratops had short, straight brow horns that grew long and curved as they grew up. The frill grew bigger compared to the skull as the animal grew up. Triceratops and its young may also have been colorful, like the birds that came from dinosaurs. Scientists think the frill may have helped Triceratops attract mates. The lead author of the 2009 study said Triceratops headgear was like a Swiss army knife, used for combat, defense or display.
Words to know
- Centrosaurus: another horned dinosaur
- ceratopsians: horned dinosaurs
- herds: animal groups
- species: kind of animal
- Cretaceous: dinosaur age
