At a Glance

Attribute	Detail
Scientific name	Triceratops horridus
Pronunciation	try-SER-ah-tops HOR-ih-dus
Name meaning	“Three-horned face”; horridus — rough or bristly
Period	Late Cretaceous
Lived	68–66 Ma
Found in	Hell Creek Formation (Montana); Lance Formation (Wyoming); Denver Formation (Colorado)
Diet	Herbivore — low-growing fibrous vegetation
Length	8–9 m (26–30 ft)
Weight	6–10 metric tons
Classification	Ceratopsidae, Chasmosaurinae

Quick Answer: Triceratops horridus was a large, heavily built herbivore that lived in North America during the final two million years of the Cretaceous period. It is best known for its three facial horns and wide solid frill, which current evidence suggests were used primarily for display and intraspecific combat. It shared its environment — and at least occasionally its interactions — with Tyrannosaurus rex.

Triceratops was one of the last non-avian dinosaurs on Earth, and one of the most heavily armed herbivores the fossil record has produced. A solid-boned frill up to a metre across, brow horns that could reach the same length, and a skull built to absorb and deliver force made it unlike almost anything alive before or since. Six entries below cover the science in full.

Diet and Feeding

Field	Detail
Diet type	Strict herbivore
Primary food sources	Flowering plants, cycads, ferns, palms, conifers
Beak type	Parrot-like; used to crop and shear fibrous vegetation
Tooth count	432–800 teeth arranged in dental batteries
Tooth mechanism	Scissor-action shear; teeth replaced continuously

For the full breakdown of feeding anatomy and behaviour, see our Triceratops diet entry.

Horns and Frill

Field	Detail
Brow horn length	Up to ~1 m (fossil core); longer in life with keratin sheath
Nasal horn	Shorter and more conical in T. horridus than in T. prorsus
Frill width	Up to ~1 m across; solid bone, no openings
Epoccipitals	19–26 small bony projections bordering the frill margin
Primary function	Display and mate selection; intraspecific combat also evidenced by healed skull fractures

Defensive use against predators is possible, but not established as the main function. See our Triceratops horns and frill entry for the full evidence.

Discovery and Fossil History

Field	Detail
First specimen	1887, Denver Formation, Colorado — collected by George Lyman Cannon
Initial identification	Misidentified as a giant prehistoric bison by Othniel Charles Marsh
Formally named	1889 by Othniel Charles Marsh
Type specimen	YPM 1820, Lance Formation, Wyoming — collected by John Bell Hatcher, 1888
Key fossil site	Hell Creek Formation, Montana
Notable modern specimen	“Horridus” — approximately 85% complete; Melbourne Museum, Australia

See our Triceratops discovery entry for the full fossil history.

Taxonomy and the Torosaurus Debate

Field	Detail
Current consensus	Triceratops and Torosaurus most likely separate genera
2010 proposal	Torosaurus was a fully mature Triceratops with frill openings developed through ontogeny
Counter-evidence	Young Torosaurus individuals identified; major structural frill differences difficult to explain by growth
Status	Debate remains open; separate genera is the current working position

See our Triceratops taxonomy and the Torosaurus debate entry for the full analysis.

Triceratops vs Tyrannosaurus rex

Feature	Triceratops horridus	Tyrannosaurus rex
Period	Late Cretaceous (68–66 Ma)	Late Cretaceous (68–66 Ma)
Length	8–9 m (26–30 ft)	~12 m (40 ft)
Weight	6–10 metric tons	~8–14 metric tons
Key weapon	Three horns, solid skull, low centre of gravity	Bone-crushing bite; serrated teeth up to 30 cm
Fossil interaction evidence	Healed bite marks on brow horn and frill; T. rex tooth marks on pelvis	Tooth embedded in Triceratops; feeding marks on carcass bones

Healed bite marks confirm that at least one Triceratops survived a T. rex attack. What the fossil record does not show is who routinely prevailed — outcomes likely varied by size, health, and circumstance. See our Triceratops vs T. Rex entry for the full fossil evidence.

Torosaurus latus — a large ceratopsid from the same period and region, most likely a separate genus, though its relationship to Triceratops was the subject of a significant reclassification debate in 2010.
Nedoceratops hatcheri — a single-specimen ceratopsid from the Lance Formation sometimes proposed as an intermediate growth stage between Triceratops and Torosaurus; taxonomic status remains contested.
Anchiceratops — an earlier ceratopsid from Canada showing the evolutionary development of the open-fenestrated frill that distinguishes many relatives from the solid-frilled Triceratops.
Styracosaurus — a ceratopsid notable for its elaborate frill spikes, frequently compared to Triceratops when discussing the display versus defence functions of ceratopsian headgear.
Pachycephalosaurus — a contemporary of Triceratops in the Hell Creek Formation, relevant as an example of another heavily modified skull structure in the same ecosystem whose primary function is also debated.

Common Questions About Triceratops

Was Triceratops the last dinosaur?

Triceratops was among the very last non-avian dinosaurs, living right up to the Cretaceous–Palaeogene extinction event 66 million years ago. Fossils have been recovered within an estimated 40,000 years of the boundary, making it one of the latest-surviving large dinosaur genera currently known.

How many Triceratops species are there?

Two species are currently recognised: Triceratops horridus and Triceratops prorsus. The two differ in horn proportions — T. prorsus has a longer nasal horn — and may represent an evolutionary sequence within the Hell Creek Formation rather than fully separate lineages. Other named species have been synonymised over time.

Did Triceratops live in herds?

The evidence is inconclusive. A small number of multi-individual bonebeds have been reported, which some researchers interpret as evidence of at least occasional gregarious behaviour. However, Triceratops is far more commonly found as an isolated individual, and no clear consensus on herding behaviour exists.

Did Triceratops have any predators other than T. rex?

T. rex is the only large theropod confirmed to have interacted with Triceratops by direct fossil evidence. Juveniles may have been vulnerable to smaller predators present in the Hell Creek ecosystem, but no fossil evidence of such interactions has been confirmed.