Dinosaurs A to Z
Ceratopsidae

Triceratops try-SAIR-uh-tops

"Three-horned face"

Triceratops silhouette
You 1.8 m (5.9 ft) tall
Triceratops 9 m (29.5 ft) long
as long as 6 people standing fingertip to fingertip
silhouette · Danny Anduza (CC0) via PhyloPic
Length
9 m (29.5 ft) — About 9 m long, 3 m tall at the hip, ~9 tonnes for the largest individuals.
Period
Late Cretaceous (68–66 Mya)
Place
North America · Western United States · Saskatchewan, Canada
Food
Herbivore — Tough low-growing plants — palms, cycads, ferns. Shearing tooth batteries sliced fibrous material like a guillotine.
Clade
Ceratopsidae Ornithischia Marginocephalia Ceratopsia Big horned ceratopsians of the Late Cretaceous.

Three horns, a great bony shield, and one of the last dinosaurs standing.

Triceratops was one of the last dinosaurs to evolve before the asteroid impact that ended the age of dinosaurs 66 million years ago. It is the textbook ceratopsian — a rhinoceros-sized plant-eater with a parrot-like beak, three horns, and a great bony frill protecting its neck.

Triceratops and Tyrannosaurus rex lived in the same place at the same time. We know they fought because some Triceratops bones carry healed T. rex bite marks — the Triceratops survived the attack long enough for the wounds to heal.

More about Triceratops

Discovery

Named by Othniel Charles Marsh · 1889 · Colorado, USA

Marsh first mistook the horn cores for those of a giant extinct bison before recognising a horned dinosaur, naming Triceratops in 1889.

From Greek tri- (three), keras (horn), and ops (face): 'three-horned face'.

Portrait of Othniel Charles Marsh
Othniel Charles Marsh · 1831–1899 The Yale paleontologist whose 'Bone Wars' rivalry with Edward Drinker Cope named dozens of dinosaurs, including Triceratops, Stegosaurus, and Allosaurus.
What was the frill actually for?
Long assumed to be armour, the frillThe bony shield extending back over the neck in ceratopsians. is now usually read as display, for species recognition and mating, though it may also have helped shed heat or anchor jaw muscles.

What we know

  • Three horns: one short over the snout, two long over the eyes.
  • Bony neck frill is solid, not the windowed kind seen in other ceratopsians.
  • Lived alongside Tyrannosaurus rex — bite marks on Triceratops bones confirm it.
  • Skull alone could be 2 m long, one of the largest of any land animal.

What we guess

  • What the frill and horns were for. Once thought to be armor against predators. Now mostly seen as display structures for attracting mates and intimidating rivals.
  • Whether young Triceratops looked different enough from adults to have been mistaken for separate species — *Torosaurus* and Triceratops may be growth stages of the same animal (still debated).
  • Whether they lived in herds. Several juveniles found together is suggestive but not conclusive.