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Origins of Triceratops and other Ceratopsid Dinosaurs

The Ceratopsids - Origins and Distribution
The Ceratopsidae Dinosaur family encompasses the quadrupedal herbivores with distinguishing facial horns and large frills. This Dinosaur family includes the well known Triceratops, which is the first Ceratopsid discovered back in 1887. There are numerous subfamilies and genera of Ceratopsid. They are classified by the shape and size of their horns, beaks, and frills.

Ceratopsids are restricted to North America and Asia (Triceratops is only found in Western North America). Primitive Ceratopsids have been found in Asia, indicating they first appeared there and then crossed over to North America on a land bridge. Once in North America, they rapidly diversified until their extinction at the end of the Cretaceous. Approximately 37 genera of Ceratopsids have been classified. Below is an image of a few genera of Ceratopsid skulls, showing the distinctly different horn and frill shapes and sizes.

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Variation in Frills and Horns of the same species

When Ceratopsids were being discovered in the early 1900's, the fragmentary remains were classified based on their frill, beak, and horn shapes. No consideration was given to juvenile vs. adult appearance and sexual dimorphism. As a result, countless species were erected.

Later as more and more fossil evidence was discovered, paleontologists realized the skull changes shape as the animal enters different stages of development. Horns and frills did not fully developed until adulthood (Farlow 327).

A great example of this is from the baby chasmosaurine ceratopsid dinosaur discovered in 2013. Currie et al, in 2016, published a paper on this baby dinosaur and compared it to adult chasmosarus specimens (Currie et al, 2016). The baby chasmosarus' frill looks completely different than the adult frill.

The Triceratops Saga... The Great Species Roundup: From 16 species to 2.

A good example of reducing the number of Ceratopsids is the Triceratops genera. Triceratops is the most commonly found Dinosaur in the Hell Creek Formation of the western United States. The Triceratops genus once had up to 16 species assigned to it based on all the different skull variations found. Once paleontologists realized the frills changed during development, Triceratops was reanalyzed. In 1986 Ostrom and Wellnhofer reduced Triceratops down to just 1 species, T. horridus. They figured all the skull differences were due to different stages of development and sexual dimorphism, and there couldn't be numerous similar large animals all living in the same area.

A little later, Catherine Forester in 1996 researched the Triceratops species and concluded since T. horridus greatly outnumbered T. prorsus, they were two distinct species. Finally, in 2009 Scannella and Fowler supported this view and the saga was over. There were two Triceratops species... sort of... There's that whole Torosaurus issue...

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Triceratops vs. Torosaurus - Triceratops is not Torosaurs

Torosaurus is a large ceratopsid found in the same formation as Triceratops. It is larger and the frill is distinctly different, being longer, with large holes near the top. In 2010 Scannella and Horner published a paper demonstrating that Torosaurus was actually a late, rapid, growth stage of Triceratops. This stirred all kinds of controversy. Paleontologists were taking sides, some agreed and some disagreed. Personally, I always had trouble with how two large holes could simply erode in the frill bone. That would really transform the entire muscle attachment structures. Within the last few years, many papers have been published refuting Scannella and Horner's results. In 2011 the ceratopsid dinosaur expert Dr. Andy Farke published a paper showing Torosaurus is "a genus distinct from Triceratops and Nedoceratops." Recent papers tend to support the separate genus, including a paper by Longrich and Field in 2012. They studied various Torosaurus and Triceratops skulls and did a clustering analysis to arrange them in growth series. They found immature and mature individuals of both Torosaurus and Triceratops. Therefore, they could be the same animal. Triceratops and Torosaurus are different Dinosaurs.
The image above is from Longrich and Field (2012). It shows an adult and a subadult Torosoarus.

Horns and Frills - They Weren't Made For Ramming!

Most of the Ceratopsids had huge frills with the exceptions of Diceratops and Triceratops. These two genera had frills that were comparatively reduced in size (Fastovsky p. 180). Increases in frill size during life directly affected jaw muscle strength (the larger the frill, the larger/stronger the jaw muscle) (Fastovsky p. 186). The big holes seen in some of the frills were probably filled with muscle attachments and/or cartilage.

As for the horns, many people forget when they see a fossil Triceratops or other Ceratopsid Dinosaurs, the horns on the skull are the bone cores. These bone cores would have been covered by the actual horns, which would have been much longer in life.

Unfortunately, it's impossible to verify what horns and frills were actually used for. However, using modern herding animals as an analogy, it's likey they were used for dominance, defense, and display. Ceratopsids may have used their horns within their own species for territorialism and mating rights. This matches the fossil evidence, as puncture wounds have been commonly found in skulls and frills of Triceratops from other Triceratops, indicating some form of intraspecies combat (Farke, et al, 2009).

A study showed that if two adult Triceratops rammed each other head on, their skulls would shatter! However, Ceratopsid horns were shaped different than any mammilian counterpart. Instead of ramming, they may have simply locked horns and fought. A study using models found it was physically possible for triceratops to engage in horn locking behavior (Farke, Andrew, A. 2004). They found 3 possible horn locking arrangements. Instead of ramming each other, they would lock horns and fight, sort of like how moose will lock horns when fighting.

It is interesting to note, that there is one exception. A different genera, Centrosaurus, a ceratopsid with only 1 large nasal horn, was studied by Farke (Farke, et al, 2009) and was found to be absent of injuries. This means Centrosaurs probably did not use their horns and frills for mating or territorial combat, but instead for display purposes, like a peacock. A firgure from Farke's paper is shown below. It shows incidence rates of showing incidence rates of lesions in (A) Triceratops and (B) Centrosaurus.

Moral of the story, if Triceratops used them for mating behavior and Centrosaurus used them for display, horns and frills were probably used in a variety of different ways by different types of ceratopsids.

One use of the horns and frills by many ceratopsids was probably to ward off predators. Some ceratopsid fossils have even been found with healed T-rex bite marks, these are specimens that have successfully staved off a T-Rex attack. While many others have been found with unhealed bite marks, meaning they were T-Rex food. Because of these fossil finds, it is not unreasunable to assume the frill and horns were also used to fend off the mighty T-Rex that lived in the Western U.S. in the late Cretaceous.

Whether horns and frills were used for horn locking, head bunting, display, defence, or all of the above, one thing is for certain. They came in all shapes and sizes, just look at the image below!

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Triceratops Behavior: Herding and Diet

Herding Behavior

Large bone beds of 100's of Centrosaur fossils have been found in the Midwest, indicating they traveled in large herds. No large bone beds of Triceratops have been found, but groups of individuals have been found together, so they may have traveled in large herds or at least smaller groups. This is consistent with the fact that horn usage is more prevalent in herding animals, such as deer, gazelle, and buffalo.

Teeth and Diet

Like all herding animals, Ceratopsids were herbivores. Their mouths were ideally suited for eating tough vegetation. These Dinosaurs had double rooted teeth that were arranged in groups called dental batteries. A dental battery is a unique tooth set-up where adjacent teeth were locked together in longitudinal rows and in vertical columns. With at least 3 teeth in each column, 1 was functional and 2 were "replacements." The teeth, which were continually replaced throughout Dinosaurs' lives, were positioned so vertically and were so sharp (self-sharpening in fact) that they could shear like scissors. During chewing, these dinosaurs' teeth really did not touch at all like humans' do; instead they slid past each other, in a slicing motion (Fastovsky 183). Because of these razor sharp teeth and very strong jaw muscles, they are often referred to as "Nature's first Cuisinarts!!" (Farlow 85). They could slice through the toughest material.
On a side note, the other common herbivores, the Hadrosaurs, had similar dental batteries.

Scientists are somewhat unsure of their exact plant diet. They suspect, due to their relatively low browsing height, they may have eaten low growing plants such as angiosperms, ferns, and small conifers growing at that height. Due to their large and heavy skulls, they could not rise up on their hind legs, but these lawnmowers of the American west may have been able to bulldoze over trees in order to gain access to the leaves.

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How fast could Triceratops Dinosaur Run?
Triceratops and Ceratopsid Locomotion

Many people assume Triceratops was a very slow and lumbersome animal. Evidence shows this is not the case.

Skeletal reconstructions of Ceratopsid Dinosaurs in many museums (including the ones pictured in this article show Triceratops with a sprawling lizard like posture. Research shows these dinosaurs should have a more mammal like posture, with the front legs underneath the animal, not splayed out to the side. The lizard like posture comes from errors when mounting the rib and vertebra of Ceratopsids.

Evidence supporting the above statements come from analysis of Triceratops and other Ceratopsian trackways. Paul and Christiansen published a paper in 2000 in which they studied the pedal impressions in trackways and analyzed the placement and angles of the hands and feet. From this information, they determined Ceratopsids have an elephant like forelimb posture. A mammal like posture enables Ceratopsids to run MUCH faster than a reptile posture. Paul and Christiansen then indicate the maximum running speed of the largest Ceratopsids to be "broadly similar to that of rhinos." By the way, The Black Rhinoceros can run at speeds around 55 km/hr, or 34 miles per hour! That's pretty darn fast!

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Triceratops Dinosaur Skin - Scales, Scutes, and Quills??

Fossilized Dinosaur skin impressions are VERY rare to find. They often dub Dinosaur fossils with skin as "Dino Mummies" although they are not mummified. The actual skin is not preserved, but impressions of the skin in the once soft mud that surrounded the animal fossilize.

Fortunately, for Triceratops lovers, a few "Ceratopsid Mummies" have been found. One of the original, shown above, AMNH 5427, is a Centrosaurus with a large patch of skin preserved.

A more recent "Triceratops Mummy" named Lane was discovered in Wyoming in 2002. The Black Hills Institute of Geological Research carefully and painstakingly excavated the T. horridus specimen. It is now on display at their museum with another almost completely intact T. horridus skeleton called Kelsey.

The Triceratops Lane has the most preserved skin than any other Dinosaur fossil found. There are areas where several feet of skin are preserved.

The skin is very different than what many paleontologists thought. The underside of the animal is covered in scutes, similar to a crocodile. The rest of the dinosaur is covered in small scales. However, there are also irregular scale like shapes. Some are fist shaped hexagons and have small pore-like holes in the center.

Some people have speculated that quills may have protruded from these holes. This "Quill" hypothesis stems from a relative of the Triceratops, Psittacosaurus from Asia. It is a distant relative that has quill like structures on the top of its tail. It is important to note that Psittacosaurur is a distant Triceratops relative, so it does not mean Triceratops would have had quills also. The "Quill" hypothesis currently lies in the realm of speculation, and we will need to wait for further studies and publications shed light on the exact nature of Triceratops skin. Below is an image of a section of skin from th Triceratops Lane.

Recommended Dinosaur Books and Educational Items:

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High quality Dinosaur teeth by Fossilera

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Currie Philip J., Holmes Robert B., J. Ryan Michael, Coy Clive. (2016) A juvenile chasmosaurine ceratopsid (Dinosauria, Ornithischia) from the Dinosaur Park Formation, Alberta, Canada. Journal of Vertebrate Paleontology, 2016; e1048348 DOI: 10.1080/02724634.2015.1048348

Farlow, O. James, Brett-Surman, M.K., Editors (1997). The Complete Dinosaur. IN: Indiana University Press.

Fastovsky, E. David, Weishampel, B. David (1996). The Evolution And Extinction Of The Dinosaurs. NY: Cambridge University Press.

Farke A.A. (2011) Anatomy and Taxonomic Status of the Chasmosaurine Ceratopsid Nedoceratops hatcheri from the Upper Cretaceous Lance Formation of Wyoming, U.S.A. PLoS ONE 6(1): e16196. doi: 10.1371/journal.pone.0016196

Farke AA, Wolff EDS, Tanke DH. (2009) Evidence of Combat in Triceratops. PLoS ONE 4(1): e4252. doi: 10.1371/journal.pone.0004252

Farke, A.A. 2004. Horn use in Triceratops (Dinosauria: Ceratopsidae): Testing behavioral hypotheses using scale models. Palaeontologia Electronica 7(1):10 pp. (PDF)

Forster Catherine A. (1996) Species resolution in Triceratops: cladistic and morphometric approaches. Journal of Vertebrate Paleontology, 16:259-270.

Longrich NR, Field DJ. (2012) Torosaurus Is Not Triceratops: Ontogeny in Chasmosaurine Ceratopsids as a Case Study in Dinosaur Taxonomy. PLoS ONE 7(2): e32623. doi:10.1371/journal.pone.0032623

Ostrom J.H, Wellnhofer P. (1986) The Munich specimen of Triceratops with a revision of the genus. Zitteliana. 14, 111-158.

Scannella J, Horner JR. (2010) Torosaurus is Triceratops, synonymy through ontogeny. Journal of Vertebrate Paleontology 30: 1157-1168.

Scannella, J.B. and D.W. Fowler. (2009) Anagenesis in Triceratops: evidence from a newly resolved stratigraphic framework for the Hell Creek Formation. North American Paleontological Convention , abstracts volume: 148-9.

Gregory S. Paul, Per Christiansen. (2000) Forelimb posture in neoceratopsian dinosaurs: implications for gait and locomotion Paleobiology Summer, v. 26 no. 3 p. 450-465

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