Of all the herbivorous dinosaurs, Triceratops is perhaps the most famous.
And for good reason! Triceratops is not only one of the first dinosaurs discovered in North America, but also one of the most famous and recognizable. With two massive, meter-long horns located above each eye, and a neck frill adorned with smaller horns across its edges, there’s no mistaking Triceratops for any other dinosaur.
Today’s article will examine Triceratops and discuss what paleontologists know about it. First, a little background information is in order. Triceratops was discovered during the bone wars of paleontology and, at first, wasn’t even considered to be a dinosaur. To say a giant set of horns found in the Denver area in 1887 stumped paleontologist Othniel Charles Marsh would be inaccurate, as O.C. believed they belonged to a massive bison. After two years and the discovery of a more complete skull, Marsh’s “Bison alticornis” would be replaced by Triceratops horridus – the horrid three horned face[i].
Triceratops is the most famous member of the Ceratopsian family of horned dinosaurs. The Ceratopsians first appeared in the Jurassic and reached their evolutionary peak during the Campanian Age of the Late Cretaceous (83-72 million years ago), where dozens of species roamed across North America and Asia. By the time Triceratops appeared at the end of the Cretaceous Period (68 million years ago), the Ceratopsians had dipped in diversity, with Triceratops being amongst the last known genera.
Triceratops fossils are found in the American states of Colorado, Wyoming, Montana, and the Dakota’s, as well as the Canadian provinces Alberta and Saskatchewan. Triceratops is amongst the most common dinosaurs known to science, with hundreds of skulls and specimens identified by paleontologists.
Though many subspecies have been named throughout the years, only two are currently valid: T. horridus and T. prorsus. The two can be differentiated based on two factors. First, T. horridus fossils are found in older deposits than T. prorsus, which may indicate that prorsus directly evolved from horridus[ii]. The second is that horridus had a smaller nasal horn and longer beak than prorsus. As dinosaurs neared their end, Triceratops horridus and prorsus dominated the landscapes of central North America.
An Absolute Tank of a Dinosaur
Triceratops was massive. At nine meters long and three meters tall, Triceratops was one of the biggest known Ceratopsians[iii]. Their skulls alone are often over three meters long, which is amongst the largest recorded sizes for terrestrial organisms. More impressive was its weight; with estimations ranging between 6 to 12 tonnes, Triceratops was bulky beyond belief. To put that into perspective, the African Elephant – the largest land mammal today – weighs between 3 to 7 tonnes. Look no further than a Triceratops femur placed next to an Elephant femur:
Life in Hell… Creek
Though Triceratops fossils are found in plenty of rock formations in North America, one location stands out. The Hell Creek formation of Montana is perhaps the most infamous in paleontology. After all, Hell Creek is the location that numerous famous dinosaurs – most notably Triceratops, Ankylosaurus, and Tyrannosaurus – called home. Triceratops fossils are particularly common, with paleontologist John Scannella noting that “it is hard to walk out into the Hell Creek Formation and not stumble upon a Triceratops weathering out of a hillside”[iv].
Does this demonstrate herding behaviours? Probably not. Though many Triceratops specimens have been discovered, very few have been found together. One of two exceptions is a bonebed of juvenile Triceratops discovered in 2009, which contained only three individuals[v]. While this still may show that juveniles Triceratops lived together, perhaps as familial units for protection, it doesn’t mean adults did. Other Ceratopsians, most notably Centrosaurus, are known from numerous bonebeds that can contain hundreds of individuals. To say the evidence of herding in Triceratops pales in comparison is putting it lightly!
What is more likely is that Triceratops lived in small groups, perhaps like modern rhinos. Though rhinos prefer to be solitary, they can occasionally be found living in ‘crashes,’ small groups that typically consist of a mother and her calves or a few females living together. This parallels a separate Triceratops bonebed from Wyoming that contains two adults and a juvenile[vi]. Instead of living in herds like other Ceratopsians, Triceratops mostly lived the way of the loner.
Frills & Horns: Love, War, or Both?
What did Triceratops use its big old horns and frill for anyways? The most famous theory is that Triceratops evolved these for protection from the biggest carnivore on the block: Tyrannosaurus rex. As I will discuss later, there is some validity to this theory. However, another popular theory proposes that Triceratops’ formidable defences were developed to combat another formidable adversary: other Triceratops.
Evidence of Triceratops using their horns to battle other members of its own species has been discovered. In 2009, injuries found on Triceratops skulls– including fractures, punctures, and overgrowth of bone – were analysed by Andrew Farke to see if they fit any sort of pattern. It turns out they did fit a pattern associated with intraspecific (single species) combat in modern animals with horns and antlers[vii]. Wounds were found mostly on the squamosal bone – the lowest section of Triceratops’ frill – which is where the horns of opposing Triceratops would have been located during headlocks.
So, it seems that Triceratops used its massive skull as a battering ram to ward off rivals. Encounters with opposing Triceratops may have had a sociosexual function, with males duking it out to secure the right to mate or hold territory[viii]. The massive frill of Triceratops wasn’t large enough to fully protect it from predation but could have been used either as display to attract females or to protect them from catastrophic wounds inflicted by another Triceratops. Who knows? Maybe their frills could have been brightly coloured to attract mates, though this theory has not yet been validated.
Smashing your skull for combat, the container of the body’s most important organ, may seem… unwise. But Triceratops is not the only herbivore to demonstrate such behaviours. The Pachycephalosaurids, or “bone-headed dinosaurs,” used their domed skulls for similar purposes. Animals like deer and rhinos do so in the present. Additionally, the first four vertebrae of Triceratops were fused together to offer extra support, meaning that they would have done well engaging in prehistoric jousting matches.
There is another piece of evidence that points towards Triceratops’ frills and horns having a role in reproduction…
Growing Up (and Into a Different Species?)
Since there are hundreds of Triceratops specimens, it shouldn’t come as a surprise that individuals of all ages have been discovered. The development of frills and horns from infant to adult is astounding and has been charted at numerous growth stages in Triceratops’ life. Whereas infants and juveniles have small frills, those of adults are massive. The development of their horns are even more spectacular, as tiny stubs hollow out, change shape, and become massive once maturity hit[ix].
The dramatic growth of Triceratops led paleontologist Jack Horner to hypothesize that fossils of another Late Cretaceous Ceratopsian, Torosaurus, are actually older Triceratops. Horner’s theory is centred on two factors. First, Torosaurus lived in the same locations at the same time as Triceratops but was significantly larger. Second, the frill of Torosaurus has two pronounced holes, which is a trait common to other Ceratopsians but not found in Triceratops[x]. Could Triceratops have developed this trait later in life?
Unfortunately for Horner, the evidence doesn’t support his theory. A 2012 study examined almost three dozen Triceratops and Torosaurus skulls to examine their ages. What researchers found was that many older skulls identified as Triceratops were found without frill holes, while some Torosaurus specimens were found to be less mature[xi]. This would be impossible under Horner’s theory, as older specimens would always be in the Torosaurus mold. Another fact working against Horner is that Chasmosaurus, a large Ceratopsian that lived slightly before Triceratops, had frill holes in both adolescence and adulthood[xii]. In other words, Torosaurus and Triceratops can both rest easy as distinct species.
Prehistoric Rivalry: Triceratops vs Tyrannosaurus rex
It is impossible to profile Triceratops without discussing its, um, “relationship” to Tyrannosaurus rex. It is common knowledge that these two titans of the Cretaceous lived alongside each other throughout North America. They must have fought each other at some point, right?
The answer is yes.
Although plenty of evidence exists of Tyrannosaurus scavenging Triceratops[xiii], one spectacular Triceratops specimen demonstrates an active conflict. Described in 2008, this unlucky Triceratops had part of its frill bitten and its left horn bitten off[xiv]. What’s incredible is that this Triceratops survived its encounter with Tyrannosaurus, demonstrating that the two had an active predator-prey relationship with each other.
Triceratops and Tyrannosaurus are the culmination of an evolutionary arms race that had been developing since the Jurassic. Everywhere the Ceratopsians went, the Tyrannosaurids weren’t far behind. As the Tyrannosaurids grew bigger and became sophisticated killing machines, the Ceratopsians evolved to become equally well defended. After almost 100 million years, a conflict which had started with dog sized dinosaurs turned into a rivalry between two of the most formidable animals the world has ever seen.
The Darling of the Ceratopsians
Triceratops is one of a handful of dinosaurs that everyone knows about. With remarkable horns and a spectacular frill, Triceratops is easily one of the most famous and recognizable dinosaurs in existence. Though it’s most striking features may not have evolved for the purposes you imagined they did, it doesn’t take away from the beauty – and power – of Triceratops.
Thank you for reading today’s article! If you’d like to know more about the ceratopsians and their most underrated and common member, I suggest you read about Psittacosaurus, “The Dinosaur That Keeps on Giving,” Here at Max’s Blogosaurus!
I do not take credit for any image found in this article.
Header image courtesy of Mark Witton.
[i] Black, Riley. “When Triceratops Was a Giant Bison.” Smithsonian.com, Smithsonian Institution, 27 May 2011, https://www.smithsonianmag.com/science-nature/when-triceratops-was-a-giant-bison-179449725/.
[iii] Prothero, Donald R. The Story of Evolution in 25 Discoveries: The Evidence and the People Who Found It. Columbia University Press, 2020.
[iv] Prothero, Donald R. The Story of Evolution in 25 Discoveries: The Evidence and the People Who Found It. Columbia University Press, 2020.
[v] Mathews, Joshua C., et al. “The First Triceratops Bonebed and Its Implications for Gregarious Behavior.” Journal of Vertebrate Paleontology, vol. 29, no. 1, 2009, pp. 286–290., https://doi.org/10.1080/02724634.2009.10010382.
[vi] Smith, Matt. “Triceratops Trio Unearthed in Wyoming.” CNN, Cable News Network, 4 June 2013, https://www.cnn.com/2013/06/03/us/triceratops-found/index.html.
[viii] Witton, Mark P., and Charles Robert Knight. Life through the Ages II: Twenty-First Century Visions of Prehistory. Indiana University Press, 2020.
[ix] Prothero, Donald R. The Story of Evolution in 25 Discoveries: The Evidence and the People Who Found It. Columbia University Press, 2020.
[x] Wong, Kate. “Are Torosaurus and Triceratops One and the Same?” Scientific American Blog Network, Scientific American, 28 Sept. 2009, https://blogs.scientificamerican.com/observations/are-torosaurus-and-triceratops-one-and-the-same/.
[xi] Longrich, Nicholas R., and Daniel J. Field. “Torosaurus Is Not Triceratops: Ontogeny in Chasmosaurine Ceratopsids as a Case Study in Dinosaur Taxonomy.” PLoS ONE, vol. 7, no. 2, 2012, https://doi.org/10.1371/journal.pone.0032623.
[xii] Currie, Philip J., et al. “A Juvenile Chasmosaurine Ceratopsid (Dinosauria, Ornithischia) from the Dinosaur Park Formation, Alberta, Canada.” Journal of Vertebrate Paleontology, vol. 36, no. 2, 2016, https://doi.org/10.1080/02724634.2015.1048348.
[xiii] Magazine, Smithsonian. “Did Tyrannosaurus Ever Battle Triceratops?” Smithsonian.com, Smithsonian Institution, 26 Oct. 2012, https://www.smithsonianmag.com/science-nature/did-tyrannosaurus-ever-battle-triceratops-95464192/.
[xiv] Brusatte, Stephen. Dinosaur Paleobiology. Wiley-Blackwell, 2012.