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Ceratosaurus is an iconic dinosaur due to numerous physical attributes that distinguish it from other theropod species: the horn on the end of its nose, the massive teeth, the tiny hands with the four fingers, the wide tail, etc. However, the main focus of this article are its osteoderms – the bony bumps that were on its back. What were they, where exactly on the body were they, and what did they look like?
Despite its instantly recognizeable profile, Ceratosaurus fossils are surprisingly rare. Only a handful of skeletons have been found, and all of them are incomplete. Of these specimens the things which are especially unlikely to be preserved are its osteoderms. These small bony lumps (there’s really no other way to describe them) occured in a row running down the middle of its back, and it is one of this animal’s more distinctive features. It is one of only two theropod species (the other being Carnotaurus) which are known to have possessed body armor. Yet “armor” is hardly the word that I would use to describe this anatomical attribute, as we shall see later.
In order to make an accurate picture of Ceratosaurus, I needed to get as much information as I could about its osteoderms. So far, nobody has done a comprehensive study of Ceratosaurus osteoderm morphology – there’s a paleontology Master’s thesis that’s just begging to be picked up by someone. There wasn’t much information to go on because written descriptions of the osteoderms are rather scant. Only a few mounted specimens of Ceratosaurus include the osteoderms as part of the display, and I’m not aware of any museum having Ceratosaurus osteoderms housed in its collections departments.
Charles W. Gilmore says the following in his description of Ceratosaurus fossils:
“Several dermal ossifications were found with the type specimen of Ceratosaurus nasicornis, and some of these were so retained in the matrix as to indicate their exact position in relation to the internal skeleton of the living animal. Reference is made here to the row of elongate, irregularly shaped, bony ossicles present above the spinous processes of caudals (fig. 1, pl. 22) 4 to 10 inclusive, and above cervicals 4 and 5 (0, pls. 29 and 30). The position of these ossicles would appear to indicate a continuous row of dermal ossifications, extending along the median line of the back from the base of the skull well down on the tail, if not the greater part of its length…The ossifications above the tail are from 25 to 38 mm above the tops of the spinous processes of the vertebrae, evidently indicating the thickness of the skin and muscles between them and the tops of the spines. Those on the neck are much closer to the vertebrae, and in one instance appears to rest on the spine (figs. 1, 2, and 3, pl. 20). That there were other dermal ossifications is shown by the presence of a small skin plate found with the bones of this skeleton. It had been freed from the matrix when it came into my hands, so there is no evidence as to its probable position in the skin. It is a relatively small subquadrangular plate of bone 58 by 70 mm., with a comparatively smooth ventral and a roughened dorsal surface. The under surface is gently concave in the direction of its shortest diameter, with a low longitudinal swelling extending through the middle of its longest diameter. The roughening of the external surface is without definite pattern” (Charles W. Gilmore, Smithsonian Institution-United States National Museum, Bulletin 110 – “Osteology of the Carnivorous Dinosauria of the United States National Museum, with a Special Reference to the genera Antrodemus (Allosaurus) and Ceratosaurus”. Washington: Government Printing Office, 1920. Pages 113-114).
Unable to examine these osteoderms in person, I did the next best thing – I looked at as many pictures of Ceratosaurus osteoderms as I possibly could, and I made the following observations:
- There was only one row of osteoderms running along the middle of its back.
- The osteoderms are all fairly small.
- The osteoderms are irregularly shaped.
- From overhead, the osteoderms appear to be diamond or lozenge-shaped, elongated anteriorally-posteriorally.
- The osteoderms were smooth underneath, but they had a rugose texture on their upper surface.
- Some osteoderms seem to come to a point on their upper surface, while others come to a low ridge, and others don’t have any raised features at all. This might be due to the fossilization process.
The appearance of the osteoderms was somewhat perplexing to me. In numerous examples of paleo-art, these bony knobs were shown as pronounced features, more or less uniform in shape, often being exposed bone or bone covered with a thin scute. However, the physical evidence doesn’t look anything like the commonly-portrayed iconography. If the osteoderms themselves were used for display purposes (as they likely were, since the use of a single row of small pieces of bone as armor would only be minimally protective), then they would have been much larger, much more pronounced, more uniform in appearance, and would have had a more “finished” look to them in order to make them more visually apparent. As they are, these formless bony lumps would have made a poor sight, and they certainly would have been of little use as armor.
The rough texture of the osteoderm’s dorsal surface implies that they had a covering of keratin atop them. Due to the irregular shape of the osteoderms, it is also implied or inferred that the osteoderms themselves were not the visual focus, but rather, what was on top of the osteoderm was. It’s possible that each of these small osteoderms served as the anchor point for a large keratinous scute which extended upwards from the dorsal surface of the osteoderm, possibly for a considerable distance. The image that comes to mind is that of the spines which are seen running along the backs of some lizards like a crest, such as the iguana.
In 1990, a specimen of Diplodocus was discovered with skin impressions, and among these were a series of iguana-like keratinous spines running along the top of the animal’s vertebrae. It’s therefore possible that Ceratosaurus might have had a similar appearance.
With all of this being considered, I decided to revise my Ceratosaurus drawing that I had made in April 2012. In the original drawing, the animal has a single row of osteoderms that form a line of low semi-circular bumps, looking very much like crocodilian armored scutes. You can see that drawing below.
Now, I changed the animal’s appearance by extending the osteoderms with the addition of a keratinous scute, shaped like the spines of a lizard (although my impression was that they actually looked more like theropod teeth). I also took the time to touch up the drawing’s overall color and smoothness. You can see the updated drawing below.
When I decided to alter the shape of the osteoderms with the addition of the erect spines, I noticed two important changes to the animal’s overall appearance. Firstly, it made the animal taller. In real life, the addition of a few inches of height would have made the animal seem bigger and more imposing than it actually was. Secondly, it gave the animal a much more intimidating appearance, like a “razorback” wild boar. This might have been helpful in disputes over carcasses or competition for mates. It is unknown whether both male and female Ceratosaurus possessed this feature because so few fossils have been found that a sexual compare-and-contrast cannot yet be performed. However, it is almost certain that the males were ornamented in this way.
I hope that you found all of this interesting. Keep your pencils sharp.
The sauropods are the definitive image of the dinosaur. Almost always, whenever one hears the word “dinosaur”, the image of the long-necked long-tailed four-legged behemoth is what immediately springs to mind. The sauropods were the dominant land herbivores during the Jurassic Period of the Mesozoic Era, and some of our best specimens come from western North America.
In the Rocky Mountains, in the states of Utah, Wyoming, and Colorado lies a massive swath of Jurassic-age rock known as the Morrison Formation. Here are found fossils of some of the most well-known and iconic dinosaur species, names that everyone knows, like Allosaurus, Ceratosaurus, Apatosaurus, Brachiosaurus, Stegosaurus, and Diplodocus. The Morrison Formation was home to a myriad of different species, and not just dinosaurs either. Other prehistoric creatures that have been found in this rock layer include pterosaurs, crocodiles, turtles, lizards, frogs, fish, mammals, and even insects.
While there are a few dinosaur names that stick in people’s memories, the Morrison Formation was home to many dinosaur species. One of them, which is largely unknown by the general public, was a sauropod called Haplocanthosaurus. Part of the reason why this animal doesn’t have the same caché to its name as other Jurassic giants is because it is known from only partial remains, its fossils are extremely rare, and because it is found in the oldest layers of the Morrison Formation, far below the fossil-rich layers of the middle and late strata that have yielded thousands of finds. This article will be an overview of this mysterious and curious, but not quite forgotten, sauropod of the Late Jurassic.
Discovery, Localities, and Dating
In the very early 20th Century, the remains of a sauropod dinosaur were found about eight miles north of Cañon City, Colorado, and they were discovered and excavated by one Mr. W. H. Utterback. In early 1903, John Bell Hatcher gave these bones the identification of Haplocanthus priscus, “the ancient simple spine” (1).
However, Hatcher soon learned that the name was already used for a prehistoric fish, and so later that year, he re-classified the dinosaur as Haplocanthosaurus, “simple-spined lizard”:
“Dr. C. R. Eastman has very courteously called my attention to the fact that the generic name Haplocanthus recently proposed by me for a new Sauropod dinosaur from the Jurassic deposits near Canyon City, Colorado, is essentially preoccupied, Agassiz having employed the name Haplocanthus for a genus of fishes. I would therefore propose the name Haplocanthosaurus for this genus of dinosaurs with simple median spines on the anterior dorsals and posterior cervicals” (2).
Later that same year, Hatcher published a lengthy and detailed description of all of the bones assigned to this new genus (3).
In fact, Hatcher was mistaken – the name Haplocanthus wasn’t already occupied after all. According to the rules of the ICZN, the original name would have been the correct one to use, except that nobody had called this creature by that name since its discovery. A proposal was submitted in 1989 to have Haplocanthosaurus as the accepted name of this creature due to its common use and the fact that Haplocanthus was not acknowledged by the paleontological community. The request was approved in 1991, and Haplocanthosaurus became the definite name of this dinosaur genus (4).
In 1954, the Cleveland Museum of Natural History really wanted a large grand dinosaur skeleton to put on display, just like the ones that were on display at the American Museum of Natural History in New York City and the Carnegie Museum in Pittsburgh. So an expedition was sent out west to bring back an attention-grabbing huge dinosaur skeleton. The expedition was led, surprisingly enough, by a college undergraduate student named Edwin Delfs (5).
Their first destination was Dinosaur National Monument, located near the Utah-Colorado border, and they hunted for fossils around that area. Unfortunately, they didn’t find anything. However, the team received a tip from some geology students from Louisiana State University that they ought to check out a site in Garden Park, located near Cañon City, Colorado. (6).
Delfs and his teammates relocated to the suggested location, and on the eastern bank of Four Mile Creek, they hit paydirt. Here were the grandiose fossils that the Cleveland Museum was looking for. However, they couldn’t dig anything up yet. The United States had entered the Atomic Age, and due to the Red Scare of the 1950s, the country was manufacturing hundreds of atomic bombs every year. In order to fuel this doomsday machine, the military needed massive amounts of uranium. Many of the fossils that had been discovered out west during the post-WWII years had been discovered accidentally by people who were prospecting for uranium deposits. Due to all of the uranium deposits in the area, Edwin Delfs first had to file a mining claim on the site before he could dig up any fossils (7).
Over the course of three digging seasons, Delfs and his team chipped away at the stone. Part of the reason why it took so long was due to the extremely hard consistency of the rock that the bones were found in. Another reason was that sudden flash floods would completely flood the excavation site, and unfortunately some of the bones were washed away before they could be saved and prepared. After three years of on-off excavations, the team uncovered a large number of vertebrae and parts of the hip. The specimen, which was substantially bigger than Haplocanthosaurus priscus, was named Haplocanthosaurus delfsi by Dr. Jack McIntosh (who is widely regarded as the greatest sauropod expert EVER) and Dr. Michael Williams who served as the curator of vertebrate paleontology at the Cleveland Museum of Natural History. The jacketed bones were brought back to the Cleveland Museum to be prepared. The skeleton was put on display, and it remains one of the main attractions at the Cleveland Museum of Natural History, where it is affectionately known by the nickname “Happy” (8).
There are currently two species of Haplocanthosaurus known to science: H. priscus and H. delfsi. Both of them are known from comparatively few remains in relation to other late Jurassic sauropods. No complete skeleton has ever been found, and there are numerous bones missing from all known specimens, including the skull; no Haplocanthosaurus skull has ever been found, which makes it difficult to precisely place this species within the dinosaur family tree. So far, we have large chunks of the neck and backbones, a shoulder blade, a few vertebrae from the base of the tail, the hip bones, a few leg bones, and that’s it. Most fossils of this animal have been found in Colorado, but one specimen was found in Montana and was nicknamed “Big Monty”. However, this specimen was found on private property, and it is in the hands of a professional fossil collector and dealer (9).
Fossils of both species of Haplocanthosaurus are found in the early and middle levels of the Morrison Formation, although it is rare within both of those levels. It is completely absent from the late Morrison. It is possible that Haplocanthosaurus lived during the latest part of the Middle Jurassic and therefore straddled the boundary between the Middle and Late divisions. However, there are so few places within North America where Middle Jurassic rocks are exposed, and the number of fossils from those rocks has been aggravatingly miniscule. So, the question of whether or not Haplocanthosaurus was a Middle Jurassic leftover that survived into the earliest parts of the Late Jurassic cannot be answered yet (10).
Haplocanthosaurus is distinctive for vertebrae that have only a single dorsal neural spine as opposed to the double-pronged V-shaped dorsal neural spines found in the diplodocid sauropods like Apatosaurus and Diplodocus. It is this anatomical feature that earned it its name “simple-spined lizard”. The neck vertebrae of Haplocanthosaurus have proportionally small centrum disks, high neural arches, a tall dorsal neural spine, and transverse spines that stick out directly sideways. Haplocanthosaurus is also noted for having femur bones that are substantially longer than the shin bones. This hints that Haplocanthosaurus was a very slow-moving animal (11).
Size measurements are difficult to pin down, because paleontologists currently recognize two species of Haplocanthosautrus: H. delfsi and H. priscus. It appears that Haplocanthosaurus priscus measured only 50 feet long, making it the smallest sauropod yet found in North America, while Haplocanthosaurus delfsi measured 70 feet long. This distinction was not known until 1988. John Foster states that H. priscus likely weighed around 23,000 pounds (10,500 kilograms) while H. delfsi weighed 46,200 pounds (21,000 kilograms). The aforementioned size measurements mean that Haplocanthosaurus priscus was one of the smallest – if not the smallest – sauropod found within the Morrison Formation (12).
Haplocanthosaurus is a bit of an oddball as far as sauropods go because paleontologists haven’t quite made up their minds as to how to classify it. Because Haplocanthosaurus is known only from partial skeletons, deciding where it fits within the sauropod cladogram has proved problematic and aggravating, and paleontologists have repeatedly shuffled this genus around according to their own perceptions.
Due to the shape of its vertebrae, which were unlike those of more advanced sauropods, John Bell Hatcher surmised that Haplocanthosaurus must be a quite primitive. In his initial research paper, he described Haplocanthosaurus as most closely resembling Morosaurus, a name that is now recognized as a junior synonym of Camarasaurus. Since we now classify Camarasaurus as a member of the sauropod group Macronaria, a group which contains species known for having boxy heads and large nostrils, it can be inferred that Hatcher would have placed Haplocanthosaurus in that group as well (13).
Except that Haplocanthosaurus wasn’t included in Macronaria alongside Camarasaurus and Brachiosaurus. It was, instead, included in the family Cetiosauridae. The cetiosaurs were a group of sauropods that are associated with the Middle Jurassic, especially in England, India, and China. One reason why Haplocanthosaurus’ designation as a cetiosaur stuck around for so long was because of the shape and size of the leg bones. Cetiosaurs are characteristic for having femurs that are noticeably longer than their fibulae and tibiae. However, some members of other sauropod groups also have unusually long femurs, so this anatomical feature is not 100% diagnostic towards cetiosaurs (14).
From its discovery until the middle 1990s, the established convention was that Haplocanthosaurus was a cetiosaurid. And then, things began to change. During the middle 1990s, paleontologists began to take a new look at sauropod phylogeny, and many felt that Haplocanthosaurus had been misplaced on the sauropod tree. In 1998, Jeffrey Wilson and Paul Sereno proposed that Haplocanthosaurus might indeed be a primitive member of Macronaria, which is closer to what John B. Hatcher was hinting at in 1903. In 1999, Jose Bonaparte proposed that Haplocanthosaurus was unique enough to warrant a family of its own, which he named Haplocanthosauridae, but this idea was not accepted by the majority of paleontologists. In the early 2000s, it was suspected that Haplocanthosaurus might actually be a very primitive member of the super family Diplodocoidea. A survey conducted in 2005 by Mike Taylor and Darren Naish failed to definitely establish where this genus ought to be placed. John Foster, the author of Jurassic West, postulated in his 2007 book that Haplocanthosaurus was either a cetiosaur or a primitive macronarian. As the 2000s transitioned to the 2010s, the idea that Haplocanthosaurus was likely a primitive diplodocoidean began to gain acceptance within the paleontological community, and this is what most paleontologists now consider Haplocanthosaurus to be (15).
Because Haplocanthosaurus possesses anatomical features found in both sauropod families, it’s possible that it is a transitional species, a “missing link”, between the cetiosaurs of the middle Jurassic and the diplodocids of the late Jurassic. However, proving such a statement is problematic because of the rarity of finds attributed to this genus. Haplocanthosaurus is known from several partial skeletons, but no skull has ever been found. That’s too bad, because a complete skull would probably settle the argument of where this genus fits on the sauropod tree.
Below is a drawing that I made of Haplocanthosaurus. Because no skull has ever been found, I decided to make a sort of half-cetiosaur half-diplodocid design. The short keratinous scutes that run along the middle of its spine are a reference to such spines (longer ones at that) being found in association with diplodocid sauropods; if this was a primitive member of that family, I’m guessing that such spines would be shorter, if it possessed any at all. The tail is somewhat shorter than what you might expect, more in keeping with a cetiosaurid than a diplodocid. The drawing was made on printer paper with a No. 2 pencil.
Haplocanthosaurus delfsi. © Jason R. Abdale. June 21, 2020.
Due to the scarcity of remains, theories about Haplocanthosaurus’ appearance and phylogenic relationship to other sauropods are largely conjectural. Museum mounts depicting Haplocanthosaurus, such as the one in Cleveland, are composites of known finds and educated guesswork. In terms of cladistics, the in-vogue assessment is that Haplocanthosaurus is a very archaic member of the super family Diplodocoidea. However, this might change in the future depending on any new finds that are uncovered. All that we can hope for is that we keep looking, and hopefully we’ll be able to uncover some more specimens of this mysterious and intriguing North American dinosaur in the years to come.
- John Bell Hatcher (February 21, 1903). “A New Sauropod Dinosaur from the Jurassic of Colorado”. Proceedings of the Biological Society of Washington, 16 (1): 1-2).
- John Bell Hatcher (1903). “A new name for the dinosaur Haplocanthus Hatcher”. Proceedings of the Biological Society of Washington, 16 (1): 100).
- John Bell Hatcher (1903). “Osteology of Haplocanthosaurus, with description of a new species, and remarks on the probable habits of the Sauropoda and the age and origin of the Atlantosaurus beds. Memoirs of the Carnegie Museum, 2: 1–72).
- John R. Foster and Mathew J. Wedel (2014). “Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass, Colorado”. Volumina Jurassica, 12 (2): 197).
- “Haplocanthosaurus: The Ghost of the Morrison Formation by Dr. Cary Woodruff CMNH Dinofest 2017”.
- “Haplocanthosaurus: The Ghost of the Morrison Formation by Dr. Cary Woodruff CMNH Dinofest 2017”.
- “Haplocanthosaurus: The Ghost of the Morrison Formation by Dr. Cary Woodruff CMNH Dinofest 2017”.
- “Haplocanthosaurus: The Ghost of the Morrison Formation by Dr. Cary Woodruff CMNH Dinofest 2017”.
- “Haplocanthosaurus: The Ghost of the Morrison Formation by Dr. Cary Woodruff CMNH Dinofest 2017”; “Is Nate Murphy Holding a Dinosaur for Ransom?”.
- John Foster, Jurassic West: The Dinosaurs of the Morrison Formation and their World. Indianapolis: Indiana University Press, 2007. Page 200.
- John Bell Hatcher (February 21, 1903). “A New Sauropod Dinosaur from the Jurassic of Colorado”. Proceedings of the Biological Society of Washington, 16 (1): 1-2; John Foster, Jurassic West: The Dinosaurs of the Morrison Formation and their World. Indianapolis: Indiana University Press, 2007. Page 200; “Haplocanthosaurus: The Ghost of the Morrison Formation by Dr. Cary Woodruff CMNH Dinofest 2017”.
- John Foster, Jurassic West: The Dinosaurs of the Morrison Formation and their World. Indianapolis: Indiana University Press, 2007. Pages 200-201.
- John Bell Hatcher (February 21, 1903). “A New Sauropod Dinosaur from the Jurassic of Colorado”. Proceedings of the Biological Society of Washington, 16 (1): 2.
- David Lambert, The Dinosaur Data Book: Facts and Fictions about the World’s Largest Creatures. New York: Avon Books, 1990. Page 65; Don Lessem and Donald F. Glut, The Dinosaur Society Dinosaur Encyclopedia. New York: Random House, Inc., 1993. Page 208; Gregory S. Paul, The Princeton Field Guide to Dinosaurs, 1st Edition. Princeton: Princeton University Press, 2010. Pages 173-177.
- Jeffrey A. Wilson and Paul C. Sereno (June 15, 1998). “Early Evolution and Higher-Level Phylogeny of Sauropod Dinosaurs”. Memoir (Society of Vertebrate Paleontology), 5: 1-68; Jose F. Bonaparte (1999). “An armoured sauropod from the Aptian of northern Patagonia, Argentina”. In Proceedings of the Second Gondwanan Dinosaur Symposium, National Science Museum Monographs #15. Y. Tomida, T. H. Rich, and P. Vickers-Rich, eds. Tokyo. Pages 1-12; Mike P. Taylor and Darren Naish (2005). “The phylogenetic taxonomy of Diplodocoidea (Dinosauria: Sauropoda)”. PaleoBios, 25 (2): 1–7; John Foster, Jurassic West: The Dinosaurs of the Morrison Formation and their World. Indianapolis: Indiana University Press, 2007. Page 188; John A. Whitlock (April 2011). “A phylogenetic analysis of Diplodocoidea (Saurischia: Sauropoda)”. Zoological Journal of the Linnean Society, 161 (4): 872–915; Emanuel Tschopp, Octávio Mateus, and Roger B. J. Benson (2015). “A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)”. PeerJ. 2015; 3: e857; “Haplocanthosaurus: The Ghost of the Morrison Formation by Dr. Cary Woodruff CMNH Dinofest 2017”.
Bonaparte Jose F. (1999). “An armoured sauropod from the Aptian of northern Patagonia, Argentina”. In Proceedings of the Second Gondwanan Dinosaur Symposium, National Science Museum Monographs #15. Y. Tomida, T. H. Rich, and P. Vickers-Rich, eds. Tokyo: 1-12.
Foster, John. Jurassic West: The Dinosaurs of the Morrison Formation and their World. Indianapolis: Indiana University Press, 2007.
John R. Foster and Mathew J. Wedel (2014). “Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison
Formation (Upper Jurassic) near Snowmass, Colorado”. Volumina Jurassica, 12 (2): 197–210. https://sauroposeidon.files.wordpress.com/2010/04/foster-and-wedel-2014-haplocanthosaurus-from-snowmass-colorado.pdf.
Hatcher, John Bell (February 21, 1903). “A New Sauropod Dinosaur from the Jurassic of Colorado”. Proceedings of the Biological Society of Washington, 16 (1): 1-2. https://www.biodiversitylibrary.org/page/2345230#page/118/mode/1up.
Hatcher, John Bell (February 21, 1903). “A new name for the dinosaur Haplocanthus Hatcher”. Proceedings of the Biological Society of Washington, 16: 100. https://www.biodiversitylibrary.org/page/2345230#page/118/mode/1up.
Lambert, David. The Dinosaur Data Book: Facts and Fictions about the World’s Largest Creatures. New York: Avon Books, 1990.
Lessem Don; Glut, Donald F. The Dinosaur Society Dinosaur Encyclopedia. New York: Random House, Inc., 1993.
Paul, Gregory S. The Princeton Field Guide to Dinosaurs, 1st Edition. Princeton: Princeton University Press, 2010.
Taylor Mike P.; Naish, Darren (2005). “The phylogenetic taxonomy of Diplodocoidea (Dinosauria: Sauropoda)”. PaleoBios, 25 (2): 1–7
Tschopp, Emanuel; Mateus, Octávio; Benson, Roger B. J. (2015). “A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)”. PeerJ. 2015; 3: e857. Published online on April 7, 2015. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4393826/.
Whitlock, John A. (April 2011). “A phylogenetic analysis of Diplodocoidea (Saurischia: Sauropoda)”. Zoological Journal of the Linnean Society, 161 (4): 872–915. Published online on January 12, 2011. https://academic.oup.com/zoolinnean/article/161/4/872/2732063
Wilson Jeffrey A.; Sereno Paul C. (June 15, 1998). “Early Evolution and Higher-Level Phylogeny of Sauropod Dinosaurs”. Memoir (Society of Vertebrate Paleontology), 5: 1-68.
Inverse. “Is Nate Murphy Holding a Dinosaur for Ransom?”, by Jacqueline Ronson (July 5, 2016). https://www.inverse.com/article/17806-sauropod-dinosaur-discovery-montana-fossil-hunter-paleontology-nate-murphy.
YouTube. ExtermCentral. “Haplocanthosaurus: The Ghost of the Morrison Formation by Dr. Cary Woodruff CMNH Dinofest 2017” (November 12, 2017). https://www.youtube.com/watch?v=-NWL7pjrPbI.
The image of Nature “red in tooth and claw” is a compelling vision which appeals to the popular imagination. Time and again, paleo-art illustrations depict dinosaurs and other prehistoric animals actively engaged in fighting, hunting, and killing. It’s a well-known fact that violence sells, and it’s also a well-known fact that the animal kingdom can sometimes be very brutal. But was the Mesozoic world really a landscape of perpetual violence and bloodshed with animals constantly engaged in the savage business of survival?
Most naturalists, biologists, and animal behaviorists today would say “probably not”. Animals do not engage in a perpetual brawl-fest with each other. Even so, animals do have violent interactions, not only among different species (inter-species combat), but also within the same species (intra-species combat). The dinosaurs were no exception to this, and we have many pieces of evidence that individuals within certain dinosaur species engaged in violent behavior towards each other.
Before I get into the particulars of the paleontological evidence, it’s important to establish some ground rules as to the sort of intra-species combat that animals engage in today, and what the dinosaurs likely engaged in during the past. Physical combat between individuals or at least physical harm inflicted by one individual upon another is typically rooted in either social or environmental causes. Animals hurt each other for a variety of reasons, but seldom is it done purely for the hell of it – only people do that. Social reasons for intra-species combat include violence associated with mating and with mate selection. Bighorn sheep rival males cranially collide with each other until one contestant or another gives up. Other individuals within numerous animal species fight each other in order to assert their right to mate. Mating-based violence can also include some very rough love – some males within certain shark species will actually bite the females in order to assert their power over the female. Speaking of this, asserting dominance is also one of the main causes for intra-species violence, regardless of whether or not mating is involved. This involves dominance within a hierarchy system, such as a lion pride or a wolf pack. Other reasons for intra-species combat are environmental, and are usually tied to the availability of food and other resources. Territorial defense in a strong motivator in this behavior, and this is strongly tied to yet another reason, which is competition of food.
Now that we have established some of the motivating factors behind why modern animals hurt each other, let’s examine the sort of intra-species combat that dinosaurs would have engaged in. For instance, many animals will kick either out of aggression, self-defense, or purely to express annoyance. One dinosaur that possibly engaged in combative kicking was the late Cretaceous ornithopod Parksosaurus. This small speedy herbivore possessed unusually long scythe-like claws on its feet. One may hypothesize that Parksosaurus engaged in kicking contests like in cockfights, or like the modern-day Australian cassowary bird. Then again, Parksosaurus could have also used these long claws for better traction when running, like the cleats on a runner’s shoes, or could have used them like digging tools to scratch into the dirt to search for food or water.
Of course, when people imagine kicking dinosaurs, the first thing that likely pops into their minds are the “raptor” dinosaurs, such as Deinonychus, Velociraptor, and Troodon. Did raptor dinosaurs, with their killing claws, do the same? The large hook-shaped toe claws were certainly used for a specific function, either ripping prey open or pinning it to the ground. I can easily imagine two bird-like raptors squabbling with each other and kicking out with their feet, like a pair of roosters, but this is purely speculative as there is no hard evidence for raptors engaging in kicking each other.
Acheroraptor. © Jason R. Abdale. July 16, 2014.
Years ago, it was proposed that another meat-eater, the late Jurassic carnivore Ceratosaurus, could momentarily balance itself on its thick tail like a kangaroo and kick out. However, this idea has since been disproven. In order for this kicking behavior to work, the tail has to be very thick and muscular and at the same time be very flexible. Ceratosaurus’ tail was deep, but thin in cross-section, more like a crocodile’s tail than a kangaroo’s. Furthermore, it only had limited up-down flexibility. For the most part, the tail was held stiff for balance, and its range of flexibility was largely confined to side-to-side motion, not up-and-down.
Ceratosaurus. © Jason R. Abdale. April 23, 2012.
Ceratosaurus is famous for having a prominent horn on the end of its nose, hence its name. However, the horn was very thin and blade-like in form, and was certainly used for display rather than offensive action. However, there were dinosaurs and other animals in the past that likely used their heads as weapons. “Head-butting”, when animals engage in combat by using their heads as hammers, possibly occurred in earlier animals, such as the dinocephalians of the Permian Period. They had thick flattened skulls, and either pressed and shoved against one another or might have collided cranium against cranium. The dinosaurs which are most associated with head-butting are the marginocephalians, “the wide skulls”, the group that includes pachycephalosaurs and ceratopsians. At first glance, their skulls seem to have been specially designed for head-on physical combat. The eponymous Pachycephalosaurus had a rounded skull that was a solid foot thick, and many scientists have automatically assumed that such skulls were used in head-butting contests, like with modern-day bighorn sheep. A recent study by the University of Wisconsin has found that 20% of pachycephalosaur skulls exhibit head trauma, suggesting with some certainty that the pachycephalosaurs did indeed engage in head-butting behavior.
Pachycephalosaurus. © Jason R. Abdale. October 19, 2013.
But what about the other members of the marginocephalians? The ceratopsians, “the horned faces”, which include the likes of Triceratops and Styracosaurus, have also been assumed to have been highly combative animals, with their spikes, horns, and frills. In recent years, the idea of these horned behemoths duking it out with each other or impaling predators on their sharpened horns has come under intense criticism. Many of their frills are dominated by wide holes which served to lighten the weight but also made them practically useless for protection. Some scientists think that the frills and horns were primarily there for display and species recognition, and their use in defense was only an afterthought.
Chasmosaurus. © Jason R. Abdale. March 31, 2016.
As you’ve probably seen by now, most of the animals which have physical features that can be used in combat are herbivores. Why? Because they sometimes have to physically fight in order to stay alive and avoid being eaten by carnivores. Aside from teeth and claws, the meat-eating theropod dinosaurs don’t seem to have much in the way of special features that would be involved in fighting, not just eating. Ceratosaurus’ nasal horn was too thin and flimsy for attacking something, and so too were the eyebrow horns of its larger contemporary Allosaurus. However, another carnivore did possess eyebrow horns which very well might have been used in fighting – Carnotaurus, one of my personal favorites. Ever since its discovery in the 1970s, paleontologists and paleo-artists have imagined this dinosaurian toro engaged in head-butting clashes with other members of its kind. However, based upon the build of the skull, it seems more likely that it was engaged in cranial “shoving matches”, in which both competitors would press their skulls against one another (hence the Velcro-like arrangement of bumps and nodules on the top of their heads in between the horns) and proceed to push and shove in a demonstration of pure muscular strength until one side or another decided that their opponent was too strong, and retreated.
While predators might not necessarily have physically struck each other with their skulls, they could have used their heads in another way that is far more common among carnivorous animals of all sorts today – face-biting. Face-biting is a way to assert dominance among individuals, especially in communal or pack-hunting societies. Several modern carnivorous animals, such as lions, foxes, and wolves, engage in this behavior. The infamous creature known as “Jane”, who might be either a Nanotyrannus or a juvenile Tyrannosaurus (to this day, nobody is exactly sure), has evidence of face-biting. Since many animals today who engage in face biting do so in order to assert their position of dominance in a pack society, this could be further evidence that this animal was itself a pack hunter, at least as a juvenile. At least one specimen of a juvenile Daspletosaurus also has evidence of face-biting. Sue the T. rex possesses marks on the jaw which were previously thought to have been the result of bites, but were later proven to have actually been caused by a bone infection.
Predators aren’t the only animals today that engage in face-biting, so there may have been herbivorous dinosaurs that engaged in the same behavior. The most likely candidate for this is the small African herbivore Heterodontosaurus. The tusks on this creature could have been wielded in actual biting, or they could have been used for fang-bearing contests like modern baboons. Many animals bear their fangs or canines when aggressive, and Heterodontosaurus possibly did this to intimidate rivals and scare off predators. Another animal that can be compared with Heterodontosaurus is the musk deer. However, their long saber-like canine teeth are grown for display, not combat. Musk deer grow huge teeth instead of growing antlers in order to over-awe rival males and to impress females.
Another possibility for serious dinosaur fights was among the sauropods. With their massive builds, any hit, no matter how light, likely would have caused some kind of damage. One modern long-necked animal that uses its body in sheer brute force is the giraffe – a rather placid-looking animal, but don’t make it angry. During the mating season, male giraffes will proceed to whack each other, swinging their long stiffened necks around like baseball bats, with the short stumpy horns on the tops of their heads inflicting some serious pounds-per-square-inch. Some sauropods, like Apatosaurus, had very massive thick necks in proportion with their body size. This leads some to speculate that Apatosaurus and its ilk used their bruiser builds to inflict bruises on others.
Apatosaurus louisae. © Jason R. Abdale. May 11, 2020.
But what about the opposite end of a sauropod? For many of them, the tail was just as long, or longer, than the neck. Tails can be effective weapons. Crocodilians and monitor lizards engage in tail whacking as a way to ward off threats. Many sauropods had thick tails, but others, like Diplodocus, have very long thin tails, and some believe that these long whip-like tails were indeed used like whips. A sharp crack across the side would make any Allosaurus wary.
Diplodocus carnegii. © Jason R. Abdale. May 11, 2020.
Of course, there are dinosaurs that almost certainly used their tails specifically for combat: the stegosaurs and the ankylosaurs. Evidence has been found for injuries inflicted by these animals upon predators, but I’m not certain if any evidence exists for stegosaur spikes or ankylosaur clubs being used upon members of their own kind. However, I can’t imagine it NOT happening.
Well, if you don’t have any biological weaponry on your side, like fangs, horns, spikes, clubs, or whatever, then raw physical force is your go-to option. There is evidence that predator species tangled with prey. The famous fossil find of a Velociraptor and a Protoceratops perpetually locked in a mutual mortal combat proves this. But this is likely an example of an attack-gone-wrong. Did dinosaurs of the same species physically grab onto and grapple with each other? Did dinosaurs wrestle, the way that some lizard species do today? Monitor lizards are a prime example of this, when two males will attack each other by essentially doing reptilian ju jitsu. Did dinosaurs wrestle? I’m not sure, but I’m leaning towards no, especially for the larger ones. Many small dinosaurs had thin delicate bones that could be easily broken, and many of the larger dinosaurs simply did not have the arm dexterity to do rough-and-tumble wrestling maneuvers the way that you see monitor lizards doing today. Furthermore, with their large size, being body-slammed to the ground would have done a lot of damage. As they say, the bigger they are, the harder they fall. Many dinosaurs show signs of physical trauma, including broken bones. Many led a very brutal life, with some skeletons being covered with injuries. For those reasons, I would say that most dinosaurs wanted to avoid intense physical combat.
Sometimes, the violence goes to its absolute extreme, and animals deliberately kill each other. Like intra-species fighting, intra-species killing has several motivating factors, both environmental and social. Animals kill each other to either reduce or totally eliminate competition over limited resources. Animals will also kill rivals to increase their own chances for mating, as well as killing the offspring of rivals to increase their own offspring’s chances for survival. As an example, new male lions that take over an existing pride will often kill all of the pride’s cubs in order to completely eliminate the legacy of the preceding male leader.
The most extreme form of intra-species combat is killing followed by cannibalism. Although it is largely taken for granted that prehistoric carnivorous animals ate their own kind under certain circumstances, there is little evidence to support this hypothesis. Some animals will kill and eat the young of other individuals in order to improve the chances of survival for their own young. Others may kill and eat their own kind out of starvation. Still others, like alligators, may view other members of their own kind as a legitimate food source, no different than any other prey item, and actively hunt, kill, and eat each other.
For a long time, it was believed with the firmest dogmatic conviction that the late Triassic dinosaur Coelophysis practiced cannibalism. However, this long-held belief has come into question upon closer examination of the famous Ghost Ranch specimens. It now appears that many of the bones which were previously believed to be inside the ribcages of others were actually lying underneath the ribcages. Furthermore, some of the bones previously identified as juvenile specimens have recently been re-identified as belonging to other reptile species. For the record, I am not stating that Coelophysis never engaged in cannibalism. I am stating that the evidence for cannibalism in this species is not as clear-cut as once believed and needs to be taken with a certain degree of doubt. If the study of paleontology has taught me anything, it’s that there is no such thing as dogma.
Coelophysis. © Jason R. Abdale. April 26, 2015.
Although there’s questionable evidence for cannibalism in Coelophysis, there is more compelling evidence in another dinosaur from the opposite end of the Mesozoic spectrum – Majungasaurus, an abelisaurid from Madagascar who lived at the very end of the Cretaceous Period. In 2007, scientists published findings that tooth marks discovered on some Majungasaurus bones matched the teeth in Majungasaurus’ jaws. So far, this is the only conclusive proof that a theropod species killed and/or ate the flesh of its own kind. I would like to say one thing, though: just because there’s evidence that an animal was cannibalized, that doesn’t necessarily mean that this individual was killed by the animal feeding off of it. As said before, scavengers will sometimes eat the dead bodies of their own kind. To them, meat is meat, no matter where it comes from. Others will not usually eat their own kind, but will do it if they’re desperate enough and cannot find other sources of food. As an example, most humans who have engaged in cannibalism do it out of necessity, not out of habit.
In conclusion, animals will hurt each other and kill each other for a variety of reasons, not only between species but also within species. Competition for mates, competition for food and territory, and establishing your position within the social hierarchy are all seen within the modern animal kingdom, and it’s highly likely that dinosaurs did the same.
Greetings all. Every child with a rough grasp of what life was like in Late Jurassic North America probably knows the Morrison Formation’s main characters. If such a child were to be asked to name the meat-eaters from that formation, the name Ornitholestes would definitely pop up, likely somewhere around third or fourth place.
Ornitholestes was a 6-foot long coelurosaurid theropod dinosaur that lived in western North America during the late Jurassic Period, 155-145 MYA. It is commonly depicted scampering about in the forest, or along the edge of the forest, or sneakily hiding in the shadows out of sight of the larger predators. With the likes of Allosaurus and Torvosaurus stomping around, it’s easy to see why paleo-artists have relegated little Ornitholestes to a bit-part on the Jurassic stage.
But I like to think that Ornitholestes‘ part was much bigger in the never-ending drama of Mesozoic life. Let’s look at its body. I’ve already stated that it was 6 feet long and was therefore about 2 feet tall – large enough to bite you on the knee. It likely weighed a hundred pounds or a smidge less than that – certainly not more. Its skull is worth looking at. Contrary to what has been commonly portrayed, it DID NOT have a little Ceratosaurus-like crest on the end of its nose. That mistake was made when a dislocated bone was mis-identified as a nasal crest. The skull was thin and deep, like a battle axe, and based upon its structure and that of its neck, it likely had a very strong bite. The teeth are small, but they are rather thick in cross-section. A powerful bite and thick teeth? This makes Ornitholestes sound like a precursor to the tyrannosaurs, and no wonder, because the tyrannosaurs are, in fact, highly-evolved coelurosaurs – the same group that Ornitholestes belonged to. The eye sockets on this baby were huge, so it is likely that Ornitholestes was a nocturnal hunter. As for its body, it was a bit on the muscular stocky side, so it was physically strong. It was equipped with long arms ending in three hook-like claws on each hand, and it had a long tail. We can also be fairly sure that Ornitholestes had a coat of thin whispy fur-like feathers on its body since other coelurosaurids that were more primitive and more advanced that Ornitholestes had feathers.
So what can we determine? It was strong for its size, its jaws could crack through eggshells and small bones, it could run, and it could grapple. In short, Ornitholestes was the hyena of the Jurassic savannah.
Hyenas are nothing to laugh at (I’m sorry, that was bad). Hyenas have a reputation for being scavengers, likely because they are commonly seen picking at the leftovers of the lions’ dinner, and because their jaws are the strongest jaws pound-for-pound of any meat-eating animal on the African plains – good for cracking through thick bones of carcasses. But in reality, hyenas are effective hunters as well. They are pack hunters, like lions or wolves, and it’s not unusual to see a gaggle of them, panting and bare-teethed, running down a zebra or a wildebeest.
Was Ornitholestes the same way? Unfortunately, fossils rarely provide evidence for animal behavior. The fact that Ornitholestes fossils are so rare doesn’t help matters. But I dare say that these carnivorous critters were a serious threat to dinosaur mothers who had eggs to protect, they likely did significant damage to hatchlings, they preyed upon smaller animals like thick-boned mammals, and assuredly were seen scavenging carcasses left by other larger meat-eating dinosaurs.
A while back, I drew a picture of Ornitholestes and posted it to this blog. However, it was an “old school” picture portraying Ornitholestes covered in scales. I have recently made an updated version, and I’m posting that image below.
In addition to the feathers, I’ve also slightly altered the shape of the skull to be a little more accurate. I always try to improve my work, and I dare say that a few years from now after my skills have improved further, I’ll make a drawing of this guy that’s even better than the one you see here.
Keep your pencils sharp, people.
Ceratosaurus nasicornis was a 20-foot theropod dinosaur which lived in western North America during the late Jurassic Period, about 155-145 million years ago. It is one of the more famous Jurassic meat-eating dinosaurs, along with Allosaurus and Ornitholestes. It is the second-most-common theropod found within the Morrison Formation.
There are several anatomical features which make this animal distinct. Firstly, and most obviously, it has a small flat horn shaped like half of a dinner plate on the end of its nose, as well as a pair of horns over the eyes. These features are almost certainly visual in nature and were not designed for combat. Many paleo-artists, notably Gregory Paul, like to show the horn as being very large and triangular. I might be wrong, but I instead decided to portray the horn as it appears on the skull – low and rounded, not tall and pointy.
This animal also has a single row of scutes or osteoderms – small knobs of bone – running down the middle of its back, extending from the back of the head all the way to the tip of the tail. Many examples of paleo-art show Ceratosaurus with multiple rows of osteoderms, like the South American abelisaurid theropod Carnotaurus. This, however, is not true – Ceratosaurus just had one row of these bony bumps.
Ceratosaurus had unusually large teeth in its upper jaw in proportion to the rest of its head. This is a clue that this particular animal engaged in what is called “hatchet-style” biting and feeding, where the animal opens its jaws as wide as it possibly can, and then forcibly slams its head downward on its prey like a guillotine.
It possessed four fingers on each hand, which indicates that it was of a much more primitive stock than contemporary theropods, which were more advanced and had only three fingers on each hand. Its primitiveness also means that Ceratosaurus was probably less intelligent than other theropods. Granted, big bad Al was no genius either.
Finally, its tail was unusually wide, and some have suggested that because of this, Ceratosaurus might have been a good swimmer.
This drawing was made with a combination of Crayola and Prismacolor colored pencils. No.2 pencil was used for shading.
Many times, paleo-artists take a feature that was found in a few species and ascribe it to entire groups. One of these trends is to portray osteoderms on the bodies of dinosaurs in their artwork. The word osteoderm literally means “skin bone”. These are small pieces of bone which are embedded in the skin, and sometimes protrude out of it so that they look like bony bumps on the dinosaur’s body. Evidence suggests that they were often covered with a keratinous scute. The most prevalent example of dinosaurs possessing osteoderms is a group called the thyreophorans, meaning “shield-bearers”, which includes the stegosaurs and ankylosaurs, but other dinosaurs have them too. At least one titanosaurid sauropod, Saltasaurus, has been found with osteoderms, and it is believed that possibly all titanosaurs had osteoderms as well.
One contentious issue regarding osteoderms is their presence in theropods, or rather, in artwork depicting theropods. There is a tendency among paleo-artists to adorn the bodies of theropod dinosaurs with rows of small osteoderms along their neck, back, and tail, and I too have been guilty of this practice. However, as far as I am aware, only two theropod dinosaurs have been found with osteoderms: Ceratosaurus (western USA and possibly Africa, Late Jurassic) and Carnotaurus (Argentina, Late Cretaceous). Both of these dinosaurs were, cladistically-speaking, primitive, and were probably closer both in appearance and genetics (and almost assuredly intelligence) to early primitive archosaurs than to later theropod groups.
In terms of appearance, Ceratosaurus was found with a single row of small osteoderms running down the middle of its back (NOT multiple parallel rows, as is often shown in some works of paleo-art), extending from the back of the skull and running all the way down to the tip of the tail. Carnotaurus was found with excellent skin impressions on portions of the body, and these showed that the body was covered in non-overlapping reptilian scales, not feathers. The scales themselves were irregular in pattern and arrangement, with some being larger and more pronounced than others. Also, on the back were arranged several parallel rows of osteoderms, spaced at regular intervals. The osteoderms became larger the closer they were to the middle of the body (medially).
In terms of cladistics, Ceratosaurus and Carnotaurus belong to the same group of theropod dinosaurs, Ceratosauria. Specifically, Ceratosaurus is a ceratosaurid and Carnotaurus is an abelisaurid, which is a slightly more advanced line. It may be possible that all theropods within Ceratosauria were adorned with osteoderms, but we cannot be 100% certain of this. However, as I said earlier, some paleo-artists have a tendency of taking a feature found in one or a few specific animals and ascribing this feature to the entire sub-group of dinosaurs. For example, a few paleontologists and paleo-artists believe that many and perhaps all sauropods had a row of keratinous spines running down the neck, back, and tail just because ONE specimen of Diplodocus was found with them. While this proves that this particular species and possibly the genus had this feature, it does not mean that all diplodocid sauropods had these keratinous spines, and it certainly doesn’t prove that all sauropods in general had this feature. The same goes for theropods. Many paleo-artists place osteoderms on their meat-eating dinosaur’s bodies simply because osteoderms have been found in association with two carnivores, and they decided to put them on virtually every theropod that they drew or sculpted.
Extrapolation is no sin. There’s nothing wrong about making an observation about something and suggesting that something else which was similar may have had identical properties. Writers and researchers do it all the time. However, I should warn people out there that there are varying degrees of extrapolation. It’s one thing to make an observation based upon the fossils of these two dinosaurs, which, as I stated before, came from the same theropod sub-division, and assume or hypothesize that other species within this particular group may have had this feature as well. It is quite another thing to take that feature and apply it to every theropod genus from Eoraptor to Velociraptor.
But what about “scutes” on dinosaurs? The term “scute” has two definitions: either it is the scale-like covering over an osteoderm, or it’s simply an unusually large thick scale. Preserved skin impressions from multiple species have shown that some dinosaurs had rows of large, thick, texturally-pronounced scutes arranged on their bodies, but these scutes did not have a bony core – therefore they can’t be classified as “osteoderms”. Examples of animals that have this feature are the stegosaur Hesperosaurus and the ceratopsian Chasmosaurus.
I may sound like I’m being self-righteous and pontificating, but I too am guilty of making wild extrapolations and assumptions when it comes to my prehistoric illustrations. A few years ago, I did an anatomical study of Tyrannosaurus rex in a running pose, and I had it with osteoderms, for no other reason other than so many other paleo-artists had pictured T. rex with osteoderms in the past. I followed the crowd and illustrated my T. rex accordingly. However, later on when I read about tyrannosaur skin impressions, I learned that these large tyrannosaurs had small pebbly skin with no osteoderms. Consequently, I revised my drawing, which you can see here.
Another example of where I might have made a mistake is in my drawing “Giganotosaurus head study”, which was showcased in an earlier post on my blog; you can see it here. The reason why I had put those rows of bony bumps on its neck and a few on its jaw was because at the time I thought that Giganotosaurus was an abelisaurid, which is a sub-division of Ceratosauria. I later learned that it wasn’t, but I didn’t want to change the picture – I think it looks nice as it is. However, I’ll be sure to learn all of the information that I can about a certain subject in the future before I draw it.
What I’m trying to do here is caution paleo-artists and aspiring paleo-artists about the dangers of making wild assumptions and extrapolations. Do your homework, do your research, and illustrate your creations as best as current science allows, and don’t do anything that you aren’t able to back up with researched facts and/or persuasive arguments.
Keep your pencils sharp.