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Torosaurus

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Introduction

Most people equate the large ceratopsian dinosaur Triceratops as the arch enemy of Tyrannosaurus. Hundreds, perhaps thousands of artworks show these two species forever locked in mortal combat. But Triceratops was not the only horned dinosaur to dwell in western North America at the end of the Cretaceous Period. There was another which just as large at Triceratops but found in far fewer numbers. It was called Torosaurus.

Discovery

In 1891, the famous fossil hunter John Bell Hatcher who had made a reputation for himself during the infamous “Bone Wars” discovered a pair of skulls (collection ID codes: YPM 1830 and YPM 1831) in Wyoming within the rocks of the Lance Formation. Later that year, they were officially named Torosaurus by Prof. Othniel Charles Marsh. Contrary to what many books and websites say, Torosaurus does not mean “bull lizard”; if this was the case, it would have been written as Taurosaurus, and it isn’t. The name is derived from the ancient Greek word τορέω (toreo), meaning “pierced” or “perforated”, and it refers to the pair of large holes in the animal’s neck frill. Marsh gave the two skulls two different species names – T. latus (YPM 1830) and T. gladius (YPM 1831) – based upon differences in the shape of the nasal horn (T. latus had a nose horn sticking straight up whereas T. gladius had a nose horn pointing slightly forwards) and the long blade-like shape of the skull’s squamosal bones of T. gladius, hence its name (1). In 1896, Marsh elaborated further on these discoveries (2).

In 1947, Edwin H. Colbert and James Bump re-examined the two Torosaurus skulls which were found in Wyoming’s Lance Formation, and they concluded that they belonged to one species, not two. Since T. latus was the name that was recorded first, this name had priority, and therefore the name T. gladius was declared invalid (3).

In 1937, a specimen was found in Utah within the North Horn Formation. In 1946, Charles W. Gilmore gave it the tentative identification of Arrhinoceratops (?) utahensis (4). In 1976, Douglas A. Lawson reclassified it as Torosaurus utahensis (5). An examination conducted in 2005 concluded that T. utahensis was indeed a separate species, and also that it was found in older strata compared to T. latus (6).

Like Triceratops, Torosaurus seems to have inhabited much of western North America. Fossils which can be definitively attributed to Torosaurus have been found in Montana (7), South Dakota (8), Wyoming (9), Colorado (10), and Utah (11). Additional specimens which might belong to Torosaurus have also been found in Alberta (12), Saskatchewan (13), North Dakota (14), New Mexico (15), and Texas (16), but their identify cannot be definitively proven at this point (17).

Description

Torosaurus latus was a very large animal, measuring 30 feet long,making it one of the largest ceratopsian dinosaurs to have lived. Its skull alone was nearly 10 feet long (18), and its neck frill alone measured 6 feet long. However, to keep the weight down, it was rather thin and it had two large openings, which would have been covered in muscle and skin. Another distinguishing difference between Torosaurus and Triceratops is that Torosaurus’ horns point straight forwards whereas Triceratops’ horns are splayed out diagonally (19).

When Torosaurus was discovered in the late 19th Century, John Bell Hatcher estimated that its skull measured 2.35 meters (7.7 feet) long (20). Then in 1933, Richard S. Lull claimed that it was even bigger, measuring 8 feet 5 inches long (21). Since this publication, paleo-art reconstructions of Torosaurus which were made during the 20th Century frequently show it as having a neck frill which was extremely long, often longer than the actual fossils suggest. Thanks to further discoveries, we now know that the neck frill of Torosaurus was about 10% shorter than the artists portrayed.

The biggest Torosaurus skull found so far belongs to a specimen nicknamed “Adam” which is housed within the Museum of Evolution, located outside of the small town of Bandholm, Denmark. Although this specimen has not yet been formally described, its skull measures just a smidge under 10 feet long! This is literally the longest skull of any known dinosaur (22).

Torosaurus latus. © Jason R. Abdale (August 9, 2026).

Where does Torosaurus fit into the ceratopsian tree? Due to its large fenestrated neck frill, one is naturally tempted to group Torosaurus with other ceratopsians of a similar appearance such as Chasmosaurus, Pentaceratops, Anchiceratops, and Arrhinoceratops. These ceratopsians are referred to as “chasmosaurines” because they belong to the ceratopsian sub-family Chasmosaurinae. In 1891, Othniel Charles Marsh hypothesized that Torosaurus came from an earlier evolutionary line than Triceratops, but he didn’t provide any evidence to support his claim (23). In 2010, it was proposed by John Scanella and Jack Horner that Triceratops and Torosaurus were actually the same animal (24). This controversial statement resulted in several studies to see if the claim could be proven or disproven. The consensus was that Triceratops and Torosaurus were indeed two distinct genera. In 2010, a phylogenic analysis of ceratopsians showed that Torosaurus was slightly basal to Triceratops, but not by much (25). Further analysis carried out in 2016 has reiterated this relationship (26). This has dramatic implications – far from Torosaurus being a “grown up” version of Triceratops as Scannella and Horner proposed, it appears that it was actually the other way around, at least from an evolutionary rather than an ontogenenetic standpoint. Triceratops is placed within the sub-family Chasmosaurinae, despite having a solid bone neck frill rather than the fenestrated neck frills common to chasmosaurine ceratopsians. This implies that Triceratops’ ancestors were similar in appearance to other typical chasmosaurines, but at some point, they branched off from that group, their frills got smaller, and the openings in the neck frill gradually disappeared.

Life

Despite being approximately the same size and living in the same environment, Torosaurus is found in far fewer numbers compared to Triceratops. It’s unclear how two large ceratopsians could inhabit the same environment without competing for resources. However, in modern-day Africa, we have several species of large antelope which live side-by-side, as well as large herbivores such as wildebeest and Cape buffalo. In a resource-heavy environment, there might have been plenty of food to go around without its resident species having to resort to niche partitioning.

Due to fossils of this animal being found in isolation, Torosaurus likely lived a solitary life or possibly in small family groups. This is unlike the massive herds of Centrosaurus, Einiosaurus, and Pachyrhinosaurus which are found in Canada, or the massive nesting colonies of Protoceratops from Mongolia.

It has been commonly assumed that Torosaurus’ enormous neck frill served as a broad canvas and was likely brightly colored or elaborately patterned (maybe both), possibly sporting a pair of large false eye spots; this is a design especially favored by paleo-artists. However, since no skin fossils or fossilized pigment cells have been found associated with Torosaurus, this is just a guess.

Post-Script

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Source Citations

  1. Marsh, Othniel Charles (1891). “Notice of new vertebrate fossils”. The American Journal of Science, volume 42, issue 249 (September 1, 1891). Pages 265-267.
  2. Marsh, Othniel Charles. The Dinosaurs of North America, Part 1. Sixteenth Annual Report of the United States Geological Survey to the Secretary of the Interior, 1894-1895. Washington, D.C.: U.S. Geological Survey, 1896. Pages 214-216.
  3. Colbert, Edwin H.; Bump, James D. (1947). “A Skull of Torosaurus from South Dakota and a Revision of the Genus”. Proceedings of the Academy of Natural Sciences of Philadelphia, volume 99 (1947). Page 102.
  4. Gilmore, Charles W. (1946). “Reptilian fauna of the North Horn Formation of central Utah”. United States Department of the Interior Geological Survey Professional Paper 210-C. Washington, DC: United States Government Printing Office, 1946. Pages 42-47.
  5. Lawson, Douglas A. (1976). “Tyrannosaurus and Torosaurus, Maestrichtian Dinosaurs From Trans-Pecos, Texas”. Journal of Paleontology, volume 50, issue 1 (January 1976). Pages 161-163.
  6. Sullivan, Robert M.; Boere, Arjan C.; Lucas, Spencer G. (2005). “Redescription of the ceratopsid dinosaur Torosaurus utahensis (Gilmore, 1946) and a revision of the genus”. Journal of Paleontology, volume 79 (2005). Pages 572, 578, 580-581.
  7. McDonald, Andrew T.; Campbell, Carl E.; Brian Thomas (2016). “A New Specimen of the Controversial Chasmosaurine Torosaurus latus (Dinosauria: Ceratopsidae) from the Upper Cretaceous Hell Creek Formation of Montana”. PLOS One, volume 11, issue 3: e0151453 (March 14, 2016).
  8. Colbert, Edwin H.; Bump, James D. (1947). “A Skull of Torosaurus from South Dakota and a Revision of the Genus”. Proceedings of the Academy of Natural Sciences of Philadelphia, volume 99 (1947). Pages 93-106.
  9. Marsh, Othniel Charles (1891). “Notice of new vertebrate fossils”. The American Journal of Science, volume 42, issue 249 (September 1, 1891). Pages 265-267.
  10. ARCGIS. “Tiny, Thornton’s Torosaurus”, by Valorie Plesha (September 18, 2018).
  11. Gilmore, Charles W. (1946). “Reptilian fauna of the North Horn Formation of central Utah”. United States Department of the Interior Geological Survey Professional Paper 210-C. Washington, DC: United States Government Printing Office, 1946. Pages 42-47; Lawson, Douglas A. (1976). “Tyrannosaurus and Torosaurus, Maestrichtian Dinosaurs From Trans-Pecos, Texas”. Journal of Paleontology, volume 50, issue 1 (January 1976). Pages 161-163.
  12. Lerbekmo, J. F.; Singh, Chaitanya; Jarzen, D. M.; Russell, Dale A. (1979). “The Cretaceous–Tertiary boundary in south-central Alberta – a revision based on additional dinosaurian and microfloral evidence”. Canadian Journal of Earth Sciences, volume 16 (September 1979). Pages 1,866-1,869; Mallon, Jordan C.; Holmes, Robert B.; Bamforth, Emily L.; Schumann, Dirk (2022). “The record of Torosaurus (Ornithischia: Ceratopsidae) in Canada and its taxonomic implications”. Zoological Journal of the Linnean Society, volume 195, issue 1 (May 2022). Pages 157-171.
  13. Tokaryk, Tim T. (1986). “Ceratopsian dinosaurs from the Frenchman Formation (Upper Cretaceous) of Saskatchewan”. Canadian Field-Naturalist, volume 100, issue 2 (1986). Pages 192-196; Mallon, Jordan C.; Holmes, Robert B.; Bamforth, Emily L.; Schumann, Dirk (2022). “The record of Torosaurus (Ornithischia: Ceratopsidae) in Canada and its taxonomic implications”. Zoological Journal of the Linnean Society, volume 195, issue 1 (May 2022). Pages 157-171.
  14. Longrich, Nicholas R.; Field, Daniel J. (2012). “Torosaurus Is Not Triceratops: Ontogeny in Chasmosaurine Ceratopsids as a Case Study in Dinosaur Taxonomy”. PLOS One, volume 7, issue 2: e32623 (February 29, 2012).
  15. Lucas, Spencer G.; Mack, Greg H.; Estep, John W. (1998). “The Ceratopsian dinosaur Torosaurus from the Upper Cretaceous McRae Formation, Sierra County, New Mexico”. In Mack, G. H.; Austin, G. S.; Barker, J. M., eds. New Mexico Geological Society Guidebook, 49th Field Conference, Las Cruces County II. Pages 223-227.
  16. Lawson, Douglas A. (1976). “Tyrannosaurus and Torosaurus, Maestrichtian Dinosaurs From Trans-Pecos, Texas”. Journal of Paleontology, volume 50, issue 1 (January 1976). Pages 158-164.
  17. Sullivan, Robert M.; Boere, Arjan C.; Lucas, Spencer G. (2005). “Redescription of the ceratopsid dinosaur Torosaurus utahensis (Gilmore, 1946) and a revision of the genus”. Journal of Paleontology, volume 79 (2005). Pages 564-582.
  18. Museum of Evolution. “This Torosaurus skeleton is the largest horned dinosaur ever discovered in the world”.
  19. YouTube. Tate Geological Museum. “Late Cretaceous Dinosaurs and Their World by Russell J. Hawley” (March 5, 2026).
  20. Hatcher, John B. (1907). “The Ceratopsia”. Monographs of the United States Geological Survey, volume 49 (1907). Page 155.
  21. Lull, R. S. (1933). “A revision of the Ceratopsia or horned dinosaurs”. Memoirs of the Peabody Museum of Natural History, volume 3, issue 3 (1933). Page 132.
  22. Museum of Evolution. “This Torosaurus skeleton is the largest horned dinosaur ever discovered in the world”.
  23. Marsh, Othniel Charles (1891). “Notice of new vertebrate fossils”. The American Journal of Science, volume 42, issue 249 (September 1, 1891). Page 266.
  24. Scannella, John B.; Horner, John R. (2010). “Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): Synonymy through ontogeny”. Journal of Vertebrate Paleontology, volume 30, issue 4 (2010). Pages 1,157-1,168.
  25. Sampson, Scott D.; Loewen, Mark A.; Farke, Andrew A.; Roberts, Eric M.; Forster, Catherine A.; Smith, Joshua A.; Titus, Alan A. (2010). “New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endimism”. PLOS One, volume 5, issue 9: e12292 (September 22, 2010).
  26. Mallon, Jordan C.; Ott, Christopher J.; Larson, Peter L.; Iuliano, Edward M.; Evans, David C. (2016). “Spiclypeus shipporum gen. et sp. nov., a Boldly Audacious New Chasmosaurine Ceratopsid (Dinosauria: Ornithischia) from the Judith River Formation (Upper Cretaceous: Campanian) of Montana, USA”. PLOS One, volume 11, issue 5: e0154218 (May 18, 2016).

Bibliography

Books

Marsh, Othniel Charles. The Dinosaurs of North America, Part 1. Sixteenth Annual Report of the United States Geological Survey to the Secretary of the Interior, 1894-1895. Washington, D.C.: U.S. Geological Survey, 1896.
https://archive.org/details/dinosaursofnorth00mars/page/214/mode/1up.

Articles

Colbert, Edwin H.; Bump, James D. (1947). “A Skull of Torosaurus from South Dakota and a Revision of the Genus”. Proceedings of the Academy of Natural Sciences of Philadelphia, volume 99 (1947). Pages 93-106.
https://www.jstor.org/stable/4064368.

Gilmore, Charles W. (1946). “Reptilian fauna of the North Horn Formation of central Utah”. United States Department of the Interior Geological Survey Professional Paper 210-C. Washington, DC: United States Government Printing Office, 1946. Pages 29-53.
https://pubs.usgs.gov/publication/pp210C.

Hatcher, John B. (1907). “The Ceratopsia”. Monographs of the United States Geological Survey, volume 49 (1907). Pages 1-198.
https://www.google.com/books/edition/The_Ceratopsia/vV5YAAAAYAAJ?hl=en&gbpv=1&dq=Hatcher,+J.+B.%3B+Marsh,+O+.C.%3B+Lull,+R.+S.+(1907).+%E2%80%9CThe+Ceratopsia%E2%80%9D.+Monographs+of+the+United+States+Geological+Survey,+volume+49+(1907).+Pages+1-198.&printsec=frontcover.

Lawson, Douglas A. (1976). “Tyrannosaurus and Torosaurus, Maestrichtian Dinosaurs From Trans-Pecos, Texas”. Journal of Paleontology, volume 50, issue 1 (January 1976). Pages 158-164.
https://www.jstor.org/stable/1303647.

Lerbekmo, J. F.; Singh, Chaitanya; Jarzen, D. M.; Russell, Dale A. (1979). “The Cretaceous–Tertiary boundary in south-central Alberta – a revision based on additional dinosaurian and microfloral evidence”. Canadian Journal of Earth Sciences, volume 16 (September 1979). Pages 1,866-1,869.

Longrich, Nicholas R.; Field, Daniel J. (2012). “Torosaurus Is Not Triceratops: Ontogeny in Chasmosaurine Ceratopsids as a Case Study in Dinosaur Taxonomy”. PLOS One, volume 7, issue 2: e32623 (February 29, 2012).
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0032623.

Lull, Richard Swann (1933). “A revision of the Ceratopsia or horned dinosaurs”. Memoirs of the Peabody Museum of Natural History, volume 3, issue 3 (1933). Pages 1-175.
https://dn721908.ca.archive.org/0/items/revisionofcerato33lull/revisionofcerato33lull.pdf.

Lucas, Spencer G.; Mack, Greg H.; Estep, John W. (1998). “The Ceratopsian dinosaur Torosaurus from the Upper Cretaceous McRae Formation, Sierra County, New Mexico”. In Mack, G. H.; Austin, G. S.; Barker, J. M., eds. New Mexico Geological Society Guidebook, 49th Field Conference, Las Cruces County II. Pages 223-227.
https://nmgs.nmt.edu/publications/guidebooks/downloads/49/49_p0223_p0227.pdf.

Mallon, Jordan C.; Ott, Christopher J.; Larson, Peter L.; Iuliano, Edward M.; Evans, David C. (2016). “Spiclypeus shipporum gen. et sp. nov., a Boldly Audacious New Chasmosaurine Ceratopsid (Dinosauria: Ornithischia) from the Judith River Formation (Upper Cretaceous: Campanian) of Montana, USA”. PLOS One, volume 11, issue 5: e0154218 (May 18, 2016).
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0154218.

Mallon, Jordan C.; Holmes, Robert B.; Bamforth, Emily L.; Schumann, Dirk (2022). “The record of Torosaurus (Ornithischia: Ceratopsidae) in Canada and its taxonomic implications”. Zoological Journal of the Linnean Society, volume 195, issue 1 (May 2022). Pages 157-171.
https://academic.oup.com/zoolinnean/article/195/1/157/6540273.

Marsh, Othniel Charles (1891). “Notice of new vertebrate fossils”. The American Journal of Science, volume 42, issue 249 (September 1, 1891). Pages 265-269.
https://ajsonline.org/article/63106-notice-of-new-vertebrate-fossils.

McDonald, Andrew T.; Campbell, Carl E.; Brian Thomas (2016). “A New Specimen of the Controversial Chasmosaurine Torosaurus latus (Dinosauria: Ceratopsidae) from the Upper Cretaceous Hell Creek Formation of Montana”. PLOS One, volume 11, issue 3: e0151453 (March 14, 2016).
https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0151453.

Sampson, Scott D.; Loewen, Mark A.; Farke, Andrew A.; Roberts, Eric M.; Forster, Catherine A.; Smith, Joshua A.; Titus, Alan A. (2010). “New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endimism”. PLOS One, volume 5, issue 9: e12292 (September 22, 2010).
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0012292.

Scannella, John B.; Horner, John R. (2010). “Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): Synonymy through ontogeny”. Journal of Vertebrate Paleontology, volume 30, issue 4 (2010). Pages 1,157-1,168.
https://www.tandfonline.com/doi/full/10.1080/02724634.2010.483632.

Sullivan, Robert M.; Boere, Arjan C.; Lucas, Spencer G. (2005). “Redescription of the ceratopsid dinosaur Torosaurus utahensis (Gilmore, 1946) and a revision of the genus”. Journal of Paleontology, volume 79 (2005). Pages 564-582.
https://www.researchgate.net/publication/250070864_REDESCRIPTION_OF_THE_CERATOPSID_DINOSAUR_TOROSAURUS_UTAHENSIS_GILMORE_1946_AND_A_REVISION_OF_THE_GENUS.

Tokaryk, Tim T. (1986). “Ceratopsian dinosaurs from the Frenchman Formation (Upper Cretaceous) of Saskatchewan”. Canadian Field-Naturalist, volume 100, issue 2 (1986). Pages 192-196.
https://www.academia.edu/1113523/Ceratopsian_dinosaurs_from_the_Frenchman_Formation_Upper_Cretaceous_Saskatchewan.

Websites

ARCGIS. “Tiny, Thornton’s Torosaurus”, by Valorie Plesha (September 18, 2018).
https://storymaps.arcgis.com/stories/16a3e0c919564b018285ed3e29127fad.

Museum of Evolution. “This Torosaurus skeleton is the largest horned dinosaur ever discovered in the world”.
https://www.museumofevolution.com/the-dinosaur-era/torosaurus.

Videos

YouTube. Tate Geological Museum. “Late Cretaceous Dinosaurs and Their World by Russell J. Hawley” (March 5, 2026).
https://www.youtube.com/watch?v=0cXOH2PAA4k

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