Triceratops horridus

Triceratops horridus was one of the largest ceratopsids and one of the most abundant large herbivores in the lower and middle Hell Creek Formation. Its enormous skull carried a short nasal horn, two elongated brow horns and a solid frill edged by small bones called epiossifications. A deep beak cropped vegetation, while vertical batteries of tightly packed teeth sliced it. Many skulls and isolated bones are known, but genuinely associated, substantially complete skeletons remain much rarer than the familiar museum mounts suggest.

Its fossils occur between approximately 68 and 66 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The skull could approach one third of total body length. Its beak and dental batteries formed a two-stage feeding system: the beak cropped plants and columns of continually replacing teeth sheared them. The frill was solid rather than pierced by the large openings seen in Torosaurus. Horn direction and frill-edge bones changed dramatically during growth, so juvenile, subadult and adult skulls can look surprisingly different. The hands bore five digits but only the inner three primarily supported weight; the hind feet had four toes.

• Very large skull with a narrow, toothless beak
• Two elongated brow horns and a shorter nasal horn
• Solid parietal-squamosal frill edged by epiossifications
• Dense dental batteries with replacement teeth stacked beneath working teeth
• Robust neck and fused front vertebrae supporting the head
• Sprawling-to-upright forelimb posture with the palms facing inward
• Powerful hind limbs and a relatively short, heavy tail

John Bell Hatcher collected the type skull YPM 1820 from the Lance Formation of Wyoming in 1888. Othniel Charles Marsh first called it Ceratops horridus early in 1889, then recognised its distinctive third horn and established the new genus Triceratops that August. The species name horridus means rough or rugged, referring to the type material's surface. Hatcher's extensive field work supplied much of the material used in The Ceratopsia, completed after his death and published by the U.S. Geological Survey in 1907.

Discovery credit: John Bell Hatcher.

Naming authors: Othniel Charles Marsh.

T. horridus inhabited warm, humid coastal lowlands crossed by rivers and floodplains near the western margin of the Western Interior Seaway. Hell Creek and Lance landscapes supported flowering plants, conifers, ferns and palms or palm-like plants. Edmontosaurus, Thescelosaurus, Ankylosaurus, small mammals, turtles, crocodilians and Tyrannosaurus shared parts of this latest-Cretaceous ecosystem.

The beak and dental batteries made Triceratops an efficient bulk herbivore, but exact preferred plants are unknown. Horns and frills could contribute to defence, visual display, species recognition and combat between individuals; healed lesions and growth changes are informative without proving one exclusive function. Most discoveries are isolated. Rare multi-individual sites—including five T. horridus individuals found together by Naturalis—show that groups sometimes formed or died together, but do not establish permanent herds with a particular social structure.

• The holotype skull YPM 1820 was first assigned to Ceratops before Marsh created Triceratops later in 1889.
• Young animals had short brow horns that curved backward; the horns rotated forward as the skull matured.
• In the Hell Creek Formation, T. horridus is concentrated lower in the rock sequence, while T. prorsus dominates higher levels, with transitional shapes between them.
• The Smithsonian's original 1905 Hatcher mount combined bones from ten Triceratops individuals; the present Deep Time animal is a digitally corrected cast.
• Naturalis prepared more than 1,200 bones and fragments from five T. horridus found together in Wyoming; the travelling herd is scheduled to return to Leiden from 2030.

A research repository is not necessarily a public exhibit. Loan and display status can change, so check with the institution before visiting.

1. 01
   The Paleobiology Database

   Open source
2. 02
   Notice of gigantic horned Dinosauria from the Cretaceous

   Othniel Charles Marsh · American Journal of Science · 1889

   Open source
3. 03
   The Ceratopsia

   John Bell Hatcher · U.S. Geological Survey Monograph 49 · 1907

   Open source
4. 04
   Major cranial changes during Triceratops ontogeny

   John R. Horner, Mark B. Goodwin · Proceedings of the Royal Society B · 2006

   Open source
5. 05
   Evolutionary trends in Triceratops from the Hell Creek Formation, Montana

   John B. Scannella, Denver W. Fowler, Mark B. Goodwin, John R. Horner · Proceedings of the National Academy of Sciences · 2014

   Open source
6. 06
   Torosaurus is not Triceratops: ontogeny in chasmosaurine ceratopsids as a case study in dinosaur taxonomy

   Nicholas R. Longrich, Daniel J. Field · PLOS ONE · 2012

   Open source
7. 07
   Meet the Dinos of Deep Time: Hatcher the Triceratops

   Smithsonian Institution · 2019

   Open source
8. 08
   Triceratops: the herd at Naturalis

   Naturalis Biodiversity Center

   Open source