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Stegosaurus

Introduction

There are over a thousand species of dinosaurs that are known to science today. Kids, it seems, are more disposed to remember these names than adults, and I have encountered several examples of children trying to impress people by rattling off as many dinosaur names as possible. In fact, it embarrasses me to state that I used to be one of these pint-sized paleontological know-it-alls. Of all of these names, there are about twenty or so that nearly everybody knows straight off the top of their heads, and Stegosaurus is unquestionably one of them.

Stegosaurus is one of the most well-known and easily-recognized dinosaurs out there. It is the definitive Jurassic armored plant-eater that everybody knows and loves. It has been consistently featured in nearly every children’s dinosaur book going back as far as the 1950s and it is a favorite subject of paleo-artists. Ask practically anybody what a Stegosaurus is, and they can describe what one looks like for you: four legs, plates on its back, spikes on its tail, and a brain the size of a walnut.

However, there are a lot of misconceptions about this iconic Jurassic armored tank, not only regarding its intelligence but also its appearance. Paleo-artists have regularly portrayed Stegosaurus as a massive hulking brute, but new science suggests that this animal was much slimmer and elegant than how it’s commonly portrayed.

 

Discovery

The first Stegosaurus fossils were discovered in Colorado during the 1870s as part of the “Bone Wars”, an intense scientific feud between Prof. Edward D. Cope of the Philadelphia Academy of Natural Sciences and Prof. Othniel Charles Marsh of Yale University in their quest to become THE paleontologist of the late 19th Century by discovering and naming more species than the other guy. When the fossils were first uncovered, Marsh looked at the large back plates and thought that they were pieces of an enormous turtle shell; it wasn’t until later that he realized that they actually came from a dinosaur. In 1877, the fossils were officially given the name Stegosaurus armatus “the armed roof lizard”, because the back plates reminded Marsh of roof shingles.

As the Bone Wars continued, more specimens of Stegosaurus were discovered. However, O. C. Marsh was not working with complete specimens – only with partial skeletons or fragments. Therefore, whenever he found a specimen that did not look EXACTLY like something that he had already seen, he automatically assumed that it was a different species. Consequently, numerous species were ascribed to Stegosaurus such as S. armatus, S. affinis, S. duplex, S. laticeps, S. sulcatus, S. ungulatus, and probably the most well-known of all of them, S. stenops. A few of these were later determined to by synonymous. However, after a long and thorough examination of the finds, it appears that there were indeed three or maybe four distinct species.

Of all of the species that have been named, Stegosaurus stenops is probably the most widely recognized simply because more skeletons have been found of this particular species than any other. Stegosaurus stenops, therefore, might have been the most common species of its genus. However, prehistoric population percentages are extremely difficult to determine because the studies tend to be very subjective rather than objective. There might also be preservation biases in fossilization which would lead to some species being more likely to fossilize than others. The number of fossils, therefore, should not always be automatically correlated to population numbers.

Illustration of the skull of Stegosaurus stenops. Illustration from The Dinosaurs of North America by Othniel Charles Marsh. Washington D.C.: U.S. Government Printing Office, 1896.

Stegosaurus stenops might be the most well-known Stegosaurus species due to the sheer number of fossil specimens that have been found, but it wasn’t the largest member of its kind. Stegosaurus stenops reached about 25 feet long, while another species named Stegosaurus ungulatus was slightly larger, reaching 30 feet long. In fact, S. ungulatus is the largest stegosaur species that we know of in the entire world. However, a stegosaur from Europe named Dacentrurus may challenge that title. The problem is that this animal is known only from partial remains, so its total length is difficult to determine. Most sources that I have seen identify it as a medium-sized animal measuring 15 to 20 feet long, and there are only a handful of finds which hint that it might have grown larger. So, for the time being, S. ungulatus still holds the world record of “biggest stegosaur ever”.

 

Anatomy

Stegosaurus has been intensely studied ever since its discovery, partly due to its novel appearance. Even so, there are a lot of misconceptions about how this animal looked which have been perpetuated over the years.

Previous restorations have shown Stegosaurus as having a short compressed body with a highly arched back, short front legs, freakishly tall back legs, and a tail that’s substantially shorter than what you would expect. This image has been copied for decades and it has become so engrained into our consciousness that we automatically assume that this is how a Stegosaurus is supposed to look. One of the things that needs to be considered is that this image was completely contrary to the majority of other stegosaur species found elsewhere in Europe, Africa, India, and China, which had longer necks, shorter legs, smoothly-curving backs, and long tails. However, we just assumed that Stegosaurus was weird and didn’t fit with the majority of stegosaur anatomy, until some new discoveries were made in the 2000s.

While a complete specimen of Stegosaurus has never been found, a skeleton of a sub-adult Stegosaurus which was discovered in 2003 in Wyoming helped to substantially change our perceptions of this animal. Named “Sophie”, this 18-foot-long skeleton was 80% complete, making it the most complete Stegosaurus skeleton ever found. It took many years to clean the skeleton up, measure it, and mount it for public display in 2014. When all of the work was done, Sophie had some noteworthy aspects to her anatomy which did not fit with the traditional image, and this compelled scientists to update their reconstructions of how Stegosaurus was supposed to look. The revised image showed this animal as having much shorter back legs, a lower back, a longer stretched-out neck, and a longer tail. The resulting image is much more sinuous and streamlined than the previous image of the brooding bruising hulk that’s been around for ages.

Below is a rough sketch that I had made sometime during the late 2000s of Stegosaurus stenops based upon the information that I had at the time. This shows how Stegosaurus was believed to appear since at least the 1980s, with its conspicuously high-arched hump back, very long rear legs, and a rather short tail.

Now, here is an updated version of how Stegosaurus stenops would have looked based upon our current understanding of this animal’s anatomy. The neck is slightly longer because this creature had more cervical vertebrae than we had previously thought. The back legs aren’t as tall as we once thought they were, and this makes the back much lower and less strongly arched. Finally, the tail is noticeably longer. The resulting image is much more in-line with what we know about other stegosaur species and doesn’t make Stegosaurus appear as freakish as it once was. This drawing was made with No.2 pencil on printer paper and was made in 1:20 scale. From the tip of its nose to the tip of its tail, this drawing measures precisely 15 inches long, which would make it 25 feet long in real life.

Stegosaurus is instantly recognizable due to its back plates and tail spikes. These physical features are, anatomically-speaking, highly transformed osteoderms. The word “osteoderm” literally means “skin bone”, and it refers to any bone object which is embedded within the skin or is visible on the body’s exterior rather than forming a part of the structural skeleton. Technically, a stegosaur’s plates and spikes are osteoderms because they are attached onto the body rather than being incorporated as part of its skeleton.

While the plates and spikes may be the most obvious features to Stegosaurus’ anatomy, there were other, more subtle aspects that provided it with a certain measure of protection. Notably, there existed a series of marble-like osteoderms covering the underside of the neck where the neck connects to the skull and extending backwards for about half of the neck’s length. This almost certainly evolved as a means to protect the carotid artery and jugular vein from being torn open by a predator, yet it’s perplexing that it would only extend halfway down the neck rather than covering the entire neck. This pebbly structure forms the equivalent of a chain-mail pixane, a type of armored throat protector which was worn by Medieval knights. My gracious thanks to Mr. Ian LaSpina for his wonderful video series on Medieval armor which let me know of the existence of such an object. Please check out his website on Medieval clothing, armor, and weapons here or his YouTube channel here.

Medieval armor researcher Ian LaSpina wearing a pixane (also called a pisan or a standard), a chain-mail collar meant to protect the throat. Image courtesy of Ian LaSpina (2014), used with permission.

As stated earlier, Stegosaurus was a genus composed of three or four species, and each of them had a slightly different appearance not only in terms of their overall size but also in their body proportions, including the size and shape of the dorsal plates. The plates of Stegosaurus ungulatus are much smaller and narrower than those of Stegosaurus stenops, and they come to a pronounced sharp point at the tip. By contrast, the plates of Stegosaurus stenops were large, wide-based, and they have somewhat rounded ends.

The number of plates that Stegosaurus possessed is difficult to determine. Various sources give numbers ranging from seventeen to twenty-two plates in total. This probably has to do with the fact that most sources lump all species of Stegosaurus together, not taking into account that different species have different appearances, including different numbers of plates running along the back. It also might be partially to do with the fact that a 100% complete specimen of Stegosaurus has never been found, and therefore we cannot be entirely certain of how many plates it indeed had. The finished drawing of Stegosaurus stenops which you see above has a total of nineteen plates.

One of the topics which has generated a sizeable amount of academic debate is how the plates were arranged on the back. The earliest reconstruction of this animal shows the plates lying down on the back like overlapping fish scales. Some artists depicted this animal as having a double row of plates with the plates arranged in pairs. For much of the late 1800s and into the early 1900s, Stegosaurus was shown with the plates arranged in a single line running down the middle of the back. However, the most common arrangement that you will see nowadays is a double line of staggered alternating plates. How far apart were these two rows from each other? That, also, is a subject of conjecture. Some reconstructions show them butted up against each other along the top of the animal’s spine, forming a V-shape when seen from the front. Other artists put a gap in between the two rows, with the wideness being largely personal interpretation.

 

Depiction of Stegosaurus ungulatus made in 1896 showing it with eight tail spikes and a single line of back plates. Public domain image, Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Stego-marsh-1896-US_geological_survey.png.

 

Depiction of Stegosaurus ungulatus by Charles Knight (1901) showing it with a double row of paired plates. Public domain image, Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Stego.jpg

 

Depiction of Stegosaurus ungulatus by G. E. Roberts (1901) showing it with a double row of alternating plates. Public domain image, Wikimedia Commons.
https://commons.wikimedia.org/wiki/File:Stegosaurus_ungulatus_Roberts_1901.png

 

One of the things that you’ll notice in my drawing is that the plates are non-symmetrical. Not only are they arranged in a staggered formation along the back instead of being arranged in pairs, but also the plates on one side are of a different size and shape to the plates on the opposite side; no two plates on any Stegosaurus’ back look exactly alike to each other.

While some older sources on dinosaurs claimed that Stegosaurus’ plates were used in defense, this idea is false. Defensive armament would be better served if the plates were lying flat upon the body like overlapping armor plates, and being substantially thickened. However, the plates stand erect upon the animal’s back, leaving the sides completely unprotected. The plates are also very thin in cross-section and they would have been easily broken if they were impacted by something. Rather, the plates were almost certainly used for display. The plates extending upwards from the animal’s spine also would have made the animal look far larger than it actually was, likely as a means to deter predators.

In life, the back plates would not have been exposed bone. Instead, they would have been covered with a protective layer of keratin – the same stuff that your fingernails are made out of. Based upon the texture of the plate’s surface, it seems highly probable that these plates were not covered in scaly skin.

In addition to the dorsal plates, another distinctive feature of Stegosaurus are the four spikes on the end of its tail. While there is no official anatomical term for this feature, this weaponized tail is nowadays commonly referred to as a “thagomizer”. The name is based upon a 1982 comic from The Far Side by Gary Larson in which the tail was named in honor of a caveman named Thag Simmons who met his maker by it. Since then, it has gained popularity within the scientific community and is now an unofficial anatomical vocabulary term. It was even referenced in the fourth episode of the 2011 BBC documentary series Planet Dinosaur.

Similar to the academic debate concerning the placement and arrangement of Stegosaurus’ dorsal plates, there has likewise been an argument concerning the placement of the tail spikes. Based upon the shape of the base of these spikes, nearly all people can agree that they were angled backwards, pointing towards the tip of the tail rather than pointing forwards or directly sideways. Unfortunately, there’s not much else that we know about the spikes’ position on the body, and this has led to a lot of varying interpretations over the years. Some reconstructions and paleo-art show the spikes sticking virtually straight up, while others show them positioned outwards horizontally; this latter position has become somewhat trendy recently. However, the vast majority of 2D and 3D reconstructions show the left and right spikes positioned in a V-shape at varying degrees, with the angle being either narrower or wider depending upon the supervising museum curator, fossil preparator, or artist. So far, nobody has been able to definitively say how the tail spikes ought to be positioned. Perhaps the only way in which this debate may be settled is if a mummy is found or if a Stegosaurus specimen is found preserved in three dimensions similar to the infamous “Dueling Dinos” find.

While no skin impressions have been found in association with Stegosaurus fossils, they have been found with a related species called Hesperosaurus. It’s based upon this find that we can make inferences about what the skin of Stegosaurus would have looked like.

In 1985, the remains of a stegosaur skeleton were discovered in north-central Wyoming in rocks dated to approximately 156 MYA, in a rock layer that marks the lowest and oldest layer of the Morrison Formation. Upon careful examination of the skeleton, it was determined that this did not belong to any known species of Stegosaurus, but was instead a previously unknown genus. In 2001, it was named Hesperosaurus, “the western lizard”. Hesperosaurus differed from Stegosaurus in that it was slightly smaller (20 feet long instead of 25-30 feet) and its plates were smaller and a bit more rounded in shape. Hesperosaurus might have been the direct ancestor of the more famous Stegosaurus, but more evidence is needed before this claim can be definitively proven.

In 1995, another stegosaur skeleton was discovered in northern Wyoming in rocks dated to approximately 155-150 MYA. This skeleton was remarkable not only due to the fact that it was nearly complete, but it also contained one spot on its body with preserved skin, located on the animal’s right side in between its front right and back right legs. It wasn’t until September of 2010, fifteen years after the skeleton was discovered, that a description of this specimen was published. It was identified as belonging to Hesperosaurus.

The skin impression from Hesperosaurus consists of small non-overlapping scales which are either round, oval, or polygonal in shape. The further up the back you go, the larger the animal’s scales become, with some of the scales becoming large, oval-shaped, and surrounded by a ring of smaller scales. Most of the body’s hexagonal scales measured 2-7mm in diameter, but the oval scales higher up on the flanks are much larger than that. One rosette measured 8x10mm in area, and another further up on the back measured 10x20mm in area. These larger scales are noticeably more rounded in texture, forming distinctive “lumps”, arranged in rows lengthwise down the body. Technically these are not true osteoderms because they do not have a bony core. Instead, they could be considered as “dermal scutes”, which are nothing more than scales, like other body scales, which just happen to be unusually large and thick compared with other scales on the body. Although it cannot be proven, it’s possible that Stegosaurus had a similar skin texture to its relative Hesperosaurus.

 

Color Patterns

While skin texture can be speculated upon with a certain degree of accuracy, skin color is something that falls entirely into the realm of guesswork. To date, no preserved pigment cells have been discovered in any stegosaur fossil. Traditionally, Stegosaurus has been depicted as being green with the back plates colored in red, orange, or pink. This color scheme has been around since the 1950s, and it has been copied so many times that many people automatically think of this image whenever they hear the word “Stegosaurus”. This contrasting color scheme of green plus some color on the red end of the spectrum is visually striking and appealing to the eye, and may be the reason why it is so commonly seen to the point of it being considered a “paleo meme” to use Darren Naish’s term. But how probable is it that Stegosaurus was colored in this way? There’s really no way to tell.

Below is a colorized rendition of my updated Stegosaurus drawing showing it garbed in a traditional color scheme consisting of a mottled green with reddish plates.

One argument can be made that Stegosaurus was probably colored in more muted tones given it lived in an environment which was dry and arid for much of the year. Such a color scheme can be seen in Fred Wierum’s artwork in which he gives his Stegosaurus a distinctly desert-themed coloration of tan and brown. Unfortunately, I was not able to gain permission to use his work on this website; you can see his painting here.

Paleo-artist and children’s author Patricia Bujard has also liveried her Stegosaurus in various desert-themed color patterns. Below are a series of Stegosaurus illustrations that she has made dated, left to right: November 9, 2016. August 2, 2017. January 4, 2018. All images © Patricia Bujard. All images are used with permission. Please check out her wonderful website, Pete’s Paleo Petshop, to view more of her lovely illustrations.

steggySteggy_update2Steggy_update3

It has also been proposed by Patricia Bujard that Stegosaurus, and possibly all stegosaurs, might have been decked out with bright color patterns that are similar to venomous snakes, poison arrow frogs, or poisonous insects. Such colors would loudly advertise that it is a dangerous animal and it would serve as a warning to potential predators to back off. A color scheme which evokes this idea is a painting of Tuojiangosaurus, a stegosaur from China, made by Brian Franczak during either the late 1980s or early 1990s. In this painting, the animal is vividly portrayed in contrasting colors of black and yellowish-orange.

Here is another colorized version of my Stegosaurus drawing portraying it in a much more un-orthodox color scheme of bright black and orange stripes with a bold yellow underside, and with plates that are patterned with red, a black edge, and bright yellow “eye spots” in the center, and with black-and-yellow striped tail spikes. The message here – Stay away from me! The stripes on the body are formed by the lines of dermal scutes that are arranged on the animal’s sides. Since we only have a small patch of preserved skin from one Hesperosaurus specimen, we cannot know how extensive these scutes were on the animal’s body or if they were arranged in any kind of pattern. However, if they were arranged in a series of horizontal lines, or at least lines that more-or-less followed the body’s contours in a front-to-back arrangement, then it’s possible that these lines of scutes might have demarcated different color areas on the body. It’s just a thought. The resulting coloration is remarkably reminiscent of Brian Franczak’s painting, even though it wasn’t intended to be.  My gracious thanks to Madame Bujard for helping me with this.

Finally, here is a colorized rendition of a Stegosaurus showing a combination of the two color patterns which you see above. It has the stereotypical mottled green body, but it has the more vibrantly-colored plates seen in the second drawing. Personally, I like this one the best.

It has come to my attention that I have quite a few illustrations portraying dinosaurs patterned in broad longitudinal black stripes, including Dryosaurus and Camptosaurus. Hmmm. I don’t like making my dinosaurs look too similar to each other, but honestly, I cannot imagine these two species looking any other way. After all, both Dryosaurus and Camptosaurus are supposed to be related to each other, being primitive iguanodonts. However, the similarity of the stripes on Stegosaurus with the previously-mentioned species was entirely coincidental.

I hope you enjoyed this article. Please like, comment, and subscribe, and as always, keep your pencils sharp.

 

Head-Butting, Face-Biting, and Tail-Whacking: Dinosaur Intra-Species Combat

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.