Period: Late Cretaceous
Order, Suborder, Family: Ornithischia, Marginocephalia, Ceratopsidae
Location: North America (Canada, United States)
Length: 30 feet (9 meters)
Triceratops is one of the most spectacular and well known of all dinosaurs. This huge animal, with its long, pointed brow horns and curving neck frill, was one of the last dinosaurs to walk the Earth. It lived to the end of the Cretaceous. Triceratops was the largest of the ceratopsians.
The first Triceratops specimen found was a set of brow horns. Othniel Marsh examined these horns in 1887 and thought they came from an extinct bison. He named the specimen Bison alticornis; he did not know that horned dinosaurs existed. Two years later, a nearly complete skull was collected from Wyoming, and Marsh quickly realized his mistake. The new skull was named Triceratops horridus in 1889, and the name of the "bison" specimen was changed to Triceratops alticornis. Over the next eight years, Marsh added eight more species to the genus.
Triceratops specimens are common and many have been collected. Paleontologist John Bell Hatcher collected more than 30 skulls in one area in Wyoming alone. In fact, so many Triceratops specimens have been found that no one knows exactly how many there are. But no complete Triceratops skeleton has ever been found.
Although paleontologists have named a large number of species of Triceratops, most probably do not exist. Even though all of these "species" differ from one another in little ways, paleontologists now realize that differences should be expected.
Each living animal is not a carbon copy of the other. It is also unlikely that so many species lived together in a small area. All the many named species of Triceratops are probably only one or two species.
The body of Triceratops was massive with a huge, barrellike ribcage and short tail. Except for its large size, it probably looked like the other large ceratopsids. It was probably not a fast animal. It had heavily built limb bones, and the front limbs were shorter than the back. It probably relied on strength rather than speed for defense.
Although the name Triceratops means "three-horned face," not all specimens had three horns. Often the nasal horn was either very short or nearly absent. However, the two brow horns, which grew out of the top of the skull over each eye, were always large and well developed. The brow horns probably had a horny covering. The base of the brow horns in Triceratops was hollow; they opened into a large space (called a sinus) above the braincase (the bone that covered the brain). Some modern animals, such as cows, goats, and sheep, also have these sinuses in the tops of their skulls. The sinus acts as a shock absorber for fights; it provides a cushion for the brain.
Some Triceratops specimens show healed wounds in their skull or frill, showing that they fought among themselves. They may have fought over females, territory, or leadership. It is also likely that the long, strong horns of Triceratops were used as weapons against predators such as Tyrannosaurus.
The frill of Triceratops was different from all other ceratopsids. It was broad and round, and the bone was thick and had no fenestrae (openings). Traces of blood vessels were present in the frill and skull. These vessels probably supplied the bone and skin with blood. Some paleontologists believe that the broad frill, with its large blood supply, may have helped heat or cool the animal. Blood flowing close to the surface would give off body heat if the air was cool, or would absorb heat if the air was hot. Triceratops could turn its frill toward the sun to warm up, or go to shade to release heat if it was too warm. Modern elephants regulate their body temperature the same way, using their huge ears.
Like the horns, the solid frill may have been used to protect Triceratops from predators or from other Triceratops. The frill may also have been for bluff; Triceratops could put its head down and point its brow horns at another animal, making the frill stand up. This made Triceratops appear larger. The frill may also have attracted a mate.
For many years, paleontologists thought that Triceratops was most closely related to the centrosaurine (or "short-frilled") ceratopsids, such as Centrosaurus and Styracosaurus. This was because the frill of Triceratops was relatively short; it was much shorter than the frills of the chasmosaurine (or "long-frilled") ceratopsids, such as Chasmosaurus and Torosaurus. However, all other features of the skull of Triceratops are like those of the Chasmosaurinae, such as long brow horns, a short nasal horn, and a long snout with a double opening of the nose. Triceratops is now considered a chasmosaurine.
Triceratops had a very long and powerful beak. Each jaw had closely packed teeth with a broad grinding surface. With its scissorlike beak and grinding teeth, Triceratops was able to bite off and chew even the toughest plants. Because its beak was narrow and pointed, it probably bit off plants with the side of its beak. Muscular cheeks held food in its mouth as it chewed.
Triceratops had a small brain; the ratio of its brain size to its body size is lower than two-legged dinosaurs, such as the duckbills and meat-eaters. Although Triceratops probably was not the smartest dinosaur, it was one of the most abundant Late Cretaceous dinosaurs. So, despite its brain size, it was very successful.
The world in which Triceratops lived looked quite modern. The landscape had modern-looking trees and shrubs. Animals that lived at the same time as Triceratops included Tyrannosaurus, Thescelosaurus, Torosaurus, Leptoceratops, Ankylosaurus, and Ornithomimus.