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Triceratops
The first specimen of Triceratops - originally named Bison alticornis.
Image from The Ceratopsia (1907) by Hatcher, Marsh, and Lull.
When Triceratops was first discovered, it was mistaken for a gigantic bison, and was given the name Bison alticornis by O.C. Marsh. It wasn't until more complete specimens were uncovered that Marsh realized the horn cores he'd thought were those of a mammal actually belonged to a dinosaur.
The first specimen of Triceratops - originally named Bison alticornis.
Image from The Ceratopsia (1907) by Hatcher, Marsh, and Lull.
As more examples of this animal were described it became increasingly
apparent that Triceratops was amazingly weird by today's standards. Triceratops has become such a well known dinosaur, we sometimes forget just how bizarre it really is. Consider its head: If you take an iguana's head, scale it up to be about a meter long and throw the beak of a parrot onto the front of its face, you're still nowhere near the level of bizarre that Triceratops has in store for you. Take a set of gigantic horns and place one over each of your Iguanaparrot's eyes. Now, just for good measure, throw a smaller horn over the nose. Weird. But wait - Triceratops isn't done yet. Now go to the back of your new friend's head and pull out a shelf of bone to, oh, about 2/3 the length of the rest of the head so that it forms a gigantic frill. Now the whole skull is nearly two meters in length (Triceratops got even larger than this). This isn't bizarre enough, so add some spikes to the border of the frill. And don't stop there, because you need some spikes on the cheeks too. Yes - now, cover pretty much the whole thing in keratin (the material that bird beaks and rhino horns are made of). Stand back and gaze upon what you've done to that poor iguana. That should give you just a glimpse of what Triceratops may have looked like in life.
What was Triceratops doing with all of its bizarre structures? Were epic battles between Triceratops and Tyrannosaurus rex the norm during the Late Cretaceous? Did Triceratops live in herds, like some dinosaurs are thought to have done - or was it a loner? Did male Triceratops use their horns and frills to intimidate each other and establish dominance? Was the frill a giant solar heat panel? What kind of plants did Triceratops eat? Did Triceratops mothers take good care of their babies? What color was Triceratops? If you went back in time and met a Triceratops, what would happen?
These are some of the questions you might ask if you start thinking about Triceratops. We probably won't have all of the answers until we figure out how to travel back to the Cretaceous and avoid being eaten long enough to find a Triceratops and see for ourselves. However, we can look for physical evidence and use it to devise testable hypotheses that will bring us closer and closer to understanding what Triceratops was really like. (That's how science works!)
There is so much variation between Triceratops skulls that, up until just a few years ago, it was thought that there were as many as sixteen different species of Triceratops all living together during the Cretaceous Period. In 1996, Catherine Forster published a paper in which she explained how she'd used morphometrics to determine that there were probably far fewer than sixteen species of Triceratops at the end of the Cretaceous. She found evidence for two species.
In 2006, Jack Horner and Mark Goodwin published a paper in which they describe how they'd compared several Triceratops skulls and discovered that the shape of the horns and the spikes bordering the frill changed as Triceratops grew up. Juvenile Triceratops all have backwards curving horns and triangular spikes around their frills. As Triceratops got older, its horns curved forward and the spikes on its frill became flattened. Based on this, they hypothesized that the horns and spikes were used as display structures which indicated maturity to other Triceratops. This sounds like a pretty good hypothesis to me - but it could be that juvenile trikes had backwards facing horns for some other reason. In science, you have to stick with the principle of parsimony - which basically means that you go with the simplest explanation for the data.
The Triceratops at the American Museum of Natural History. Complete skeletons of Triceratops
are actually very rare while isolated skulls are quite common. This skeleton is made up of
a number of indivduals.
are actually very rare while isolated skulls are quite common. This skeleton is made up of
a number of indivduals.
What was Triceratops doing with all of its bizarre structures? Were epic battles between Triceratops and Tyrannosaurus rex the norm during the Late Cretaceous? Did Triceratops live in herds, like some dinosaurs are thought to have done - or was it a loner? Did male Triceratops use their horns and frills to intimidate each other and establish dominance? Was the frill a giant solar heat panel? What kind of plants did Triceratops eat? Did Triceratops mothers take good care of their babies? What color was Triceratops? If you went back in time and met a Triceratops, what would happen?
These are some of the questions you might ask if you start thinking about Triceratops. We probably won't have all of the answers until we figure out how to travel back to the Cretaceous and avoid being eaten long enough to find a Triceratops and see for ourselves. However, we can look for physical evidence and use it to devise testable hypotheses that will bring us closer and closer to understanding what Triceratops was really like. (That's how science works!)
There is so much variation between Triceratops skulls that, up until just a few years ago, it was thought that there were as many as sixteen different species of Triceratops all living together during the Cretaceous Period. In 1996, Catherine Forster published a paper in which she explained how she'd used morphometrics to determine that there were probably far fewer than sixteen species of Triceratops at the end of the Cretaceous. She found evidence for two species.
In 2006, Jack Horner and Mark Goodwin published a paper in which they describe how they'd compared several Triceratops skulls and discovered that the shape of the horns and the spikes bordering the frill changed as Triceratops grew up. Juvenile Triceratops all have backwards curving horns and triangular spikes around their frills. As Triceratops got older, its horns curved forward and the spikes on its frill became flattened. Based on this, they hypothesized that the horns and spikes were used as display structures which indicated maturity to other Triceratops. This sounds like a pretty good hypothesis to me - but it could be that juvenile trikes had backwards facing horns for some other reason. In science, you have to stick with the principle of parsimony - which basically means that you go with the simplest explanation for the data.
A juvenile Triceratops skull at the Museum
of the Rockies. Juveniles all have backwards
curving horns and triangular spikes on their frills.
of the Rockies. Juveniles all have backwards
curving horns and triangular spikes on their frills.
Even though Triceratops has been known to science for 120 years, that doesn't mean that it has nothing left to teach us about the history of life on this planet. We are constantly learning new things about Triceratops and its closest relatives, the other horned dinosaurs. In early 2009, a paper in the Journal of Vertebrate Paleontology called attention to the discovery of a Triceratops bone bed - that is, a number of Triceratops all found at the same place. Many horned dinosaur species have been found in huge bone beds, suggesting that they may have lived and traveled in gigantic herds. Triceratops, on the other hand, had not been found in massive bone beds and so it was proposed that Triceratops may have lived a more solitary life. The authors of the 2009 bone bed paper hypothesized that the discovery of several Triceratops in the same area suggested that it too may have lived in herds. On top of that, based on the fact that all of the Triceratops that they had found in the bone bed were not fully mature, they speculated that Triceratops may have traveled in groups of animals of all roughly the same age.
Also in 2009, Andrew Farke, Ewan Wolff, and Darren Tanke published the results of a study on apparent pathologies (the results of disease or injury) on the skulls of Triceratops. The paper suggests that since these marks are found in consistent locations on the frills of Triceratops that it may mean that the horns and frill were not just for visual display, but may have also been used for head to head combat.
Also in 2009, Andrew Farke, Ewan Wolff, and Darren Tanke published the results of a study on apparent pathologies (the results of disease or injury) on the skulls of Triceratops. The paper suggests that since these marks are found in consistent locations on the frills of Triceratops that it may mean that the horns and frill were not just for visual display, but may have also been used for head to head combat.
Two Triceratops engaged in combat - perhaps over territory. Was this a common sight in the Late Cretaceous of North America? (artwork copyright Lukas Panzarin, used with permission).
Two years after O.C. Marsh named Triceratops, he named another large horned dinosaur that had lived at the same time: Torosaurus latus. While somewhat resembling Triceratops, Torosaurus was distinguished by its greatly expanded cranial frill. Unlike the frill of Triceratops, which was solid, Torosaurus had two large openings in the central bone of its frill (the parietal).
A Triceratops skull viewed from above. The frill of Triceratops is composed of three bones - the parietal (in red) and two squamosals (in green). Image modified from Hatcher et al. 1907.
Torosaurus skull viewed from above. The frill of Torosaurus is noticeably different from that of Triceratops. The squamosals (green) are very elongate and the parietal has two large holes (called 'fenestrae'). Image modified from Marsh 1892.
As part of my PhD research, I've been studying Triceratops ontogeny (development from an embryo to an adult) with Jack Horner at the Museum of the Rockies. In 2010 we published a paper in the Journal of Vertebrate Paleontology proposing that Torosaurus actually represents the adult form of Triceratops. In other words, the frill of Triceratops changed shape as the animal got older and eventually became very expanded, thin, and fenestrated (it developed the characteristic holes of Torosaurus). This hypothesis is supported by multiple lines of evidence including comparative morphological studies of over a hundred Triceratops specimens ranging in size from small babies to animals with skulls the size of small cars and analyses of the microstructure of Triceratops and Torosaurus bones. If you look at the parietal of a Triceratops, beyond a certain growth stage there are thin regions which eventually developed into fenestrae as the frill expanded. Analysis of these areas under a microscope reveals that they were actively eroding in life. All of this evidence suggests that Torosaurus actually is Triceratops - so, our classic image of an adult Triceratops needs an update.
Our classic image of Triceratops (left) and the new adult face of Triceratops, previously called Torosaurus (right). Image copyright Holly Woodward, used with permission.
We are learning that some dinosaur skulls changed radically as the animals matured. In Triceratops, the horns completely changed orientation, the spikes bordering the frill became flattened, and the frill expanded and developed holes. In 2009, Jack Horner and Mark Goodwin found evidence of extreme ontogenetic change in the 'dome-headed' dinosaur Pachycephalosaurus. Throughout growth, Pachycephalosaurus developed a huge dome on its skull and at the same time it grew long spikes at the back of its skull and then these spikes eroded away to nearly nothing. Weird. In 1975, Peter Dodson discovered that some duck-billed dinosaurs developed elaborate crests on their skulls very late in ontogeny. He noted that given the transformation that some dinosaurs underwent throughout growth, different growth stages could easily be mistaken for distinct species. This appears to be what happened with Triceratops and Torosaurus and with three species of pachycephalosaur which are now recognized as growth stages of Pachycephalosaurus. It is likely that many of the dinosaur species recognized today actually represent growth stages of other dinosaurs.
Dodson, P. 1975. Taxonomic implications of relative growth in lambeosaurine hadrosaurs. Systematic Zoology 24: 37-54.
Farke AA, Wolff EDS, Tanke DH. 2009. Evidence of Combat in Triceratops. PLoS ONE 4(1): e4252. doi:10.1371/journal.pone.0004252
Forster, C.A. 1996. Species resolution in Triceratops: cladistic and morphometric approaches. Journal of Vertebrate Paleontology 16:259-270.
Horner, J.R. and M.B. Goodwin. 2009. Extreme cranial ontogeny in the Upper Cretaceous dinosaur Pachycephalosaurus. PLoS ONE 4(10): e7626.
Hatcher, J.B., O.C. Marsh, and R.S. Lull. 1907. The Ceratopsia. US Geological Survey Monograph 49:1-300.
Horner, J.R., and M.B. Goodwin. 2006. Major cranial changes during Triceratops ontogeny. Proceedings of the Royal Society of London B. 273: 2757-2761.
Marsh, O.C. 1892. The skull of Torosaurus. American Journal of Science 43: 81-84.
Mathews, J.C., Brusatte, S.L., Williams, S.A., and Henderson, M.D. 2009. The first Triceratops bonebed and its implications for gregarious behavior. Journal of Vertebrate Paleontology 29: 286-290.
Scannella, J.B. and J.R. Horner. 2010. Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny. Journal of Vertebrate Paleontology 30 (4): 1157-1168.
Two years after O.C. Marsh named Triceratops, he named another large horned dinosaur that had lived at the same time: Torosaurus latus. While somewhat resembling Triceratops, Torosaurus was distinguished by its greatly expanded cranial frill. Unlike the frill of Triceratops, which was solid, Torosaurus had two large openings in the central bone of its frill (the parietal).
Torosaurus skull viewed from above. The frill of Torosaurus is noticeably different from that of Triceratops. The squamosals (green) are very elongate and the parietal has two large holes (called 'fenestrae'). Image modified from Marsh 1892.
As part of my PhD research, I've been studying Triceratops ontogeny (development from an embryo to an adult) with Jack Horner at the Museum of the Rockies. In 2010 we published a paper in the Journal of Vertebrate Paleontology proposing that Torosaurus actually represents the adult form of Triceratops. In other words, the frill of Triceratops changed shape as the animal got older and eventually became very expanded, thin, and fenestrated (it developed the characteristic holes of Torosaurus). This hypothesis is supported by multiple lines of evidence including comparative morphological studies of over a hundred Triceratops specimens ranging in size from small babies to animals with skulls the size of small cars and analyses of the microstructure of Triceratops and Torosaurus bones. If you look at the parietal of a Triceratops, beyond a certain growth stage there are thin regions which eventually developed into fenestrae as the frill expanded. Analysis of these areas under a microscope reveals that they were actively eroding in life. All of this evidence suggests that Torosaurus actually is Triceratops - so, our classic image of an adult Triceratops needs an update.
Our classic image of Triceratops (left) and the new adult face of Triceratops, previously called Torosaurus (right). Image copyright Holly Woodward, used with permission.
We are learning that some dinosaur skulls changed radically as the animals matured. In Triceratops, the horns completely changed orientation, the spikes bordering the frill became flattened, and the frill expanded and developed holes. In 2009, Jack Horner and Mark Goodwin found evidence of extreme ontogenetic change in the 'dome-headed' dinosaur Pachycephalosaurus. Throughout growth, Pachycephalosaurus developed a huge dome on its skull and at the same time it grew long spikes at the back of its skull and then these spikes eroded away to nearly nothing. Weird. In 1975, Peter Dodson discovered that some duck-billed dinosaurs developed elaborate crests on their skulls very late in ontogeny. He noted that given the transformation that some dinosaurs underwent throughout growth, different growth stages could easily be mistaken for distinct species. This appears to be what happened with Triceratops and Torosaurus and with three species of pachycephalosaur which are now recognized as growth stages of Pachycephalosaurus. It is likely that many of the dinosaur species recognized today actually represent growth stages of other dinosaurs.
References:
Dodson, P. 1975. Taxonomic implications of relative growth in lambeosaurine hadrosaurs. Systematic Zoology 24: 37-54.
Farke AA, Wolff EDS, Tanke DH. 2009. Evidence of Combat in Triceratops. PLoS ONE 4(1): e4252. doi:10.1371/journal.pone.0004252
Forster, C.A. 1996. Species resolution in Triceratops: cladistic and morphometric approaches. Journal of Vertebrate Paleontology 16:259-270.
Horner, J.R. and M.B. Goodwin. 2009. Extreme cranial ontogeny in the Upper Cretaceous dinosaur Pachycephalosaurus. PLoS ONE 4(10): e7626.
Hatcher, J.B., O.C. Marsh, and R.S. Lull. 1907. The Ceratopsia. US Geological Survey Monograph 49:1-300.
Horner, J.R., and M.B. Goodwin. 2006. Major cranial changes during Triceratops ontogeny. Proceedings of the Royal Society of London B. 273: 2757-2761.
Marsh, O.C. 1892. The skull of Torosaurus. American Journal of Science 43: 81-84.
Mathews, J.C., Brusatte, S.L., Williams, S.A., and Henderson, M.D. 2009. The first Triceratops bonebed and its implications for gregarious behavior. Journal of Vertebrate Paleontology 29: 286-290.
Scannella, J.B. and J.R. Horner. 2010. Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny. Journal of Vertebrate Paleontology 30 (4): 1157-1168.
e-mail: jscannella (at) gmail dot com
Copyright John Scannella
JohnScannella.com: Where Triceratops Lives.
Content of this site does not necessarily reflect the views of people or organizations to whom I link.
This site is currently under construction - please bear with me.
Copyright John Scannella
JohnScannella.com: Where Triceratops Lives.
Content of this site does not necessarily reflect the views of people or organizations to whom I link.
This site is currently under construction - please bear with me.
