Open Paleo

Triceratops

Marsh, 1889 try-SERR-uh-tops /traɪˈsɛrətɒps/

From Greek tri (three), keras (horn) and ops (face); meaning "three-horned face", referring to the paired supraorbital horn-cores and the median nasal horn-core that ornament the skull.

72.2–66.0 million years ago Maastrichtian, Late Cretaceous
Late Cretaceous stages

Triceratops is the best-known ceratopsid dinosaur and among the most recognizable of all non-avian dinosaurs, defined by its three large facial horns, prominent toothless beak and solid, unfenestrated parietal-squamosal frill. Marsh erected the genus in 1889 by transferring Marsh's earlier Ceratops horridus (Marsh, 1889) to the new combination Triceratops horridus, on a partial skull (later cataloged YPM 1820) recovered from the "Laramie" — now Lance — Formation of Wyoming. Through the 1890s and early 1900s Marsh and others named more than a dozen further species, of which only two are currently accepted today (T. horridus, the type, and T. prorsus), both restricted to the latest Maastrichtian of the Western Interior of North America. Forster (1996) sank most nominal species into one of these two through a cladistic and morphometric revision; Scannella and colleagues (2014) subsequently documented a stratigraphic pattern in the Hell Creek Formation suggesting a primarily anagenetic transition from T. horridus low in the section to T. prorsus near the K-Pg boundary. Several other names (T. galeus, T. sulcatus, T. maximus, T. eurycephalus, T. albertensis) rest on inadequate material and are now treated as nomina dubia. The proposed synonymy of Torosaurus with mature Triceratops (Scannella and Horner, 2010) has not been broadly accepted in subsequent literature (Longrich and Field 2012; Maiorino and colleagues 2013) and is not adopted.

Diagnosis

  1. Three large facial horns: paired supraorbital horn-cores plus a median nasal horn formed by the epinasal, seated on coossified nasals.
  2. Edentulous premaxillae fronting an unpaired rostral bone (os rostrale) anterior to the premaxillae, forming a projecting toothless beak.
  3. Parietal-squamosal frill solid and unfenestrated, extremely thick and heavily vascularized on its dorsal surface.
  4. Squamosal short and broad with convex, rounded lateral margins; never thinned or fenestrated.
  5. Frill saddle-shaped in dorsal aspect, with an upturned caudal margin and a strong parietal midline ridge.
  6. Epoccipital ossifications fused along the parietal-squamosal margin, with one epoccipital spanning the midline of the parietal.
  7. Frontal fontanelle small and circular, or absent in mature individuals, due to closure of the frontoparietal sutures.
  8. Huge occipital portion of the frill extending posteriorly and laterally, bent ventrally at the sides to overhang the neck.

Species (2)

Triceratops horridus (Marsh, 1889)

Type species

First named as Ceratops horridus

From Latin horridus (rough, bristly), referring to the heavily ornamented occipital crest that frames the back of the skull in Marsh's holotype.

Holotype
YPM 1820 , Yale Peabody Museum of Natural History
Material
Partial skull with paired supraorbital horn-cores, a median nasal horn-core on coossified nasals, edentulous premaxillae, rostral bone, and a posteriorly extended occipital crest; estimated at least two meters long.
Horizon
Lance Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
the canyon entering Buck Creek from the west, about 100 yards above Hatchers Springs, at the Johnson Brothers' sheep ranch, Wyoming, United States

Synonyms

  • Ceratops horridus reassigned

    Original combination; named by Marsh (1889) as Ceratops horridus and transferred later that year by Marsh (1889) to the new genus as Triceratops horridus.

  • Triceratops calicornis junior subjective

    Sunk into T. horridus by Forster (1996).

  • Triceratops elatus junior subjective

    Sunk into T. horridus by Forster (1996).

  • Triceratops flabellatus junior subjective

    Sunk into T. horridus by Forster (1996); no consistent morphological characters distinguish it. The genus Sterrholophus (Marsh, 1891) is based on the same material.

  • Triceratops obtusus junior subjective

    Sunk into T. horridus by Forster (1996).

  • Triceratops serratus junior subjective

    Sunk into T. horridus by Forster (1996).

Triceratops prorsus Marsh, 1890

From Latin 'prorsus' (straight forward), for the forward-directed nasal horn.

Holotype
YPM 1822 , Yale Peabody Museum of Natural History
Material
Skull with closed frontal fontanelle, relatively short supraorbital horns, a long forward-inclined nasal horn, and a short, convexly rounded rostrum; basal skull length 88 cm.
Horizon
middle Lance Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
north side of Dry Creek, about 3 miles above its mouth into Lance Creek, about 100 yards above the site of YPM 1823, Wyoming, United States
Diagnosis
  1. Frontal fontanelle absent, closed by fusion of frontals and parietals
  2. Supraorbital horns relatively short, horn length to basal skull length ratio 0.61 or less
  3. Rostrum relatively deep and short, with a convexly rounded rostral margin
  4. Nasal horn long, curved, and forward-inclined (30-50 degrees from vertical), extending anterior to the external nares
  5. Massive horn cores with a narrow, extensive frill bearing broadly convex squamosals

Synonyms

  • Triceratops brevicornus junior subjective

    Sunk into T. prorsus by Forster (1996); shares the derived characters (closed frontal fontanelle, short supraorbital horns, short rounded rostrum) of that species.

Synonyms of the genus

Name Type Reason
Sterrholophus junior subjective Erected by Marsh (1891) for Marsh's own species Triceratops flabellatus, and returned to Triceratops by Hatcher (1907). Forster (1996) refers its holotype YPM 1821 to Triceratops horridus.
Ugrosaurus junior subjective Generally interpreted in subsequent literature (Forster 1993; Lehman 1998) as a juvenile or pathological Triceratops horridus.

Notable specimens

  • “Lane”

    HMNS PV.1506 Houston Museum of Nature and Science Found 2002 exceptional preservation

    Nearly complete skeleton from the Zerbst Ranch, Wyoming, preserved with large areas of fossil skin over its trunk, recorded in positive relief by clay templating. Scales bear conical projections suggesting possible bristles or quills.

    Bell et al. (2022)

  • MWC 7584

    Museums of Western Colorado, Dinosaur Journey largest individual

    The largest-known Triceratops skull, estimated at 2.5 meters long when complete, reaching almost a third of the entire animal's length.

    Scannella & Horner (2010)

  • “Big John”

    pathology

    Large individual (about 8 meters long, estimated to have lived around 60 years) whose squamosal bears a fenestra apparently caused by another Triceratops horn, with the bone showing significant healing, cited as evidence of intraspecific combat using the horns.

    D'Anastasio et al. (2022)

References

  1. Bell, P. R.; Hendrickx, C.; Pittman, M.; Kaye, T. G.; Mayr, G. (2022). The exquisitely preserved integument of Psittacosaurus and the scaly skin of ceratopsian dinosaurs. Communications Biology 5(1): 809. Springer Science and Business Media LLC. doi:10.1038/s42003-022-03749-3 bell2022a
  2. Scannella, J.; Horner, J. R. (2010). Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny. Journal of Vertebrate Paleontology 30(4): 1157-1168. doi:10.1080/02724634.2010.483632 scannella2010a
  3. D'Anastasio, R.; Cilli, J.; Bacchia, F.; Fanti, F.; Gobbo, G.; Capasso, L. (2022). Histological and chemical diagnosis of a combat lesion in Triceratops. Scientific Reports 12(1): 3941. Springer Science and Business Media LLC. doi:10.1038/s41598-022-08033-2 d'anastasio2022a
  4. Marsh, O. C. (1889). Notice of new American Dinosauria. American Journal of Science 37(220): 331-336. doi:10.2475/ajs.s3-37.220.331

    Names Ceratops horridus.

    marsh1889b
  5. Marsh, O. C. (1889). Notice of gigantic horned Dinosauria from the Cretaceous. American Journal of Science s3-38(224): 173-175. American Journal of Science (AJS). doi:10.2475/ajs.s3-38.224.173

    Erects the genus Triceratops by reassigning Ceratops horridus (Marsh, 1889) to the new combination T. horridus, and additionally names T. flabellatus and T. galeus.

    marsh1889a
  6. Forster, C. A. (1996). Species resolution in Triceratops: cladistic and morphometric approaches. Journal of Vertebrate Paleontology 16(2): 259-270. doi:10.1080/02724634.1996.10011313

    Reduces the historic 16 nominal Triceratops species to two valid species (T. horridus, T. prorsus) by cladistic and morphometric analysis, and establishes the modern generic diagnosis.

    forster1996a
  7. Scannella, J. B.; Fowler, D. W.; Goodwin, M. B.; Horner, J. R. (2014). Evolutionary trends in Triceratops from the Hell Creek Formation, Montana. Proceedings of the National Academy of Sciences 111(28): 10245-10250. doi:10.1073/pnas.1313334111

    Documents a stratigraphic transition through the Hell Creek Formation from T. horridus (lower) through transitional morphologies to T. prorsus (upper), favored as primarily anagenetic.

    scannella2014a
  8. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the appearance features.

    paul2024a
  9. Marsh, O. C. (1888). A new family of horned Dinosauria, from the Cretaceous. American Journal of Science s3-36(216): 477-478. doi:10.2475/ajs.s3-36.216.477

    Names Ceratops montanus, the type species of Ceratops.

    marsh1888b
  10. Maiorino, L.; Farke, A. A.; Kotsakis, T.; Piras, P. (2013). Is Torosaurus Triceratops? Geometric morphometric evidence of Late Maastrichtian ceratopsid dinosaurs. PLoS ONE 8(11): e81608. Public Library of Science (PLoS). doi:10.1371/journal.pone.0081608

    Morphometric evidence against the Torosaurus-Triceratops synonymy.

    maiorino2013a
  11. Forster, C. A. (1993). Taxonomic validity of the ceratopsid dinosaur Ugrosaurus olsoni (CoBabe and Fastovsky). Journal of Paleontology 67(2): 316-318. Cambridge University Press (CUP). doi:10.1017/S0022336000032273

    Assessed the validity of Ugrosaurus olsoni relative to Triceratops.

    forster1993a
  12. Lehman, T. M. (1998). A gigantic skull and skeleton of the horned dinosaur Pentaceratops sternbergi from New Mexico. Journal of Paleontology 72(5): 894-906. Cambridge University Press (CUP). doi:10.1017/S0022336000027220

    Interpreted Ugrosaurus as a juvenile or pathological Triceratops.

    lehman1998a
  13. Lull, R. S. (1915). The mammals and horned dinosaurs of the Lance Formation of Niobrara County, Wyoming. American Journal of Science s4-40(238): 319-348. American Journal of Science. doi:10.2475/ajs.s4-40.238.319

    Mentioned the unpublished name Triceratops ingens without description.

    lull1915a
  14. Longrich, N. R.; Field, D. J. (2012). Torosaurus is not Triceratops: ontogeny in chasmosaurine ceratopsids as a case study in dinosaur taxonomy. PLoS ONE 7(2): e32623. Public Library of Science (PLoS). doi:10.1371/journal.pone.0032623

    Argued Torosaurus is distinct from Triceratops, rejecting the synonymy.

    longrich2012b
  15. Marsh, O. C. (1890). Description of new dinosaurian reptiles. American Journal of Science s3-39(229): 81-86. American Journal of Science (AJS). doi:10.2475/ajs.s3-39.229.81

    Names Triceratops prorsus, the second currently-accepted species of the genus.

    marsh1890b
  16. Hatcher, J. B.; Marsh, O. C.; Lull, R. S. (1907). The Ceratopsia. Monographs of the United States Geological Survey 49: 1-300. United States Geological Survey. hatcher1907a
  17. Marsh, O. C. (1891). Restoration of Triceratops. American Journal of Science s3-41(244): 339-342. doi:10.2475/ajs.s3-41.244.339 marsh1891b