The number one rule of the Taphonomy Club is don’t talk about marks on bones … without placing them in context. Many marks on bones could have multiple causes, such as putative cut marks caused by stone tools on animal bones found on early hominid sites. In that case, hard sharp stony objects in the ground can cause marks that are hard to tell apart from stone tool marks. But when you find almost all the possible stone tool marks in the exact locations they would be if a hominid was butchering or defleshing the animal, then you can assert that that butchery or defleshing with stone tools was highly likely to have happened.
A similar logic has been applied by paleontologists DWE Hone and DH Tanke in their study of the fossil remains of a dinosaur from Dinosaur Provincial Park in Alberta, Canada. The dinosaur exhibits numerous bite marks, and apparently (unlike stone tool cut marks) identification of these marks as caused by carnivorous dinosaur teeth is not in question. But the location of the marks and other features allowed these scientists to argue that some sort of combat regularly occurred between members of members of the same species, or similar species, during the animal’s life. Given what is known about animal behavior and the kinds of dinosaurs around at the time, they claim that it is most likely combat between members of the same species.
The dinosaur in question is a juvenile Daspletosaurus. This is a genus of dinosaur extant in western North America between 77 and 74 million years ago (Late Cretaceous).
Since everyone knows all about Tyrannosaurus, it is helpful to compare Daspletosaurus to Tyrannosaurus. Daspletosaurus was smaller and older. Daspletosaurus ranged around 8 or 9 meters long and 2.5 tonnes, while Tyrannosaurus could be over 12 meters long and 10 tonnes. Tyrannosaurus also lived later (68 million years ago up to about the time of the great extinction). Both had short arms but Daspletosaurus’s arms were longer. Note that this kind of dinosaur, suborder Theropoda, gave rise to birds.
This particular juvenile Daspletosaurus was well preserved. Many of the bones are present, and their position in the matrix that bore them is not too far off from anatomical location. A good number of the missing bones may have actually eroded away after this part of the bone bed was exposed by erosion. There are marks on some of the bones that indicate post-death scavenging. But, most of the tooth marks are of the kind one would expect if a theropod dinosaur was biting it, and most interestingly, most of these marks show evidence of healing, and all but one mark indicating damage is on the head. Normally, theropod inflicted bite marks are found on various different bones of their prey. It appears that this individual was engaged in combat with other individuals of the same sort … other theropods. And, since this is probably the only theropod of this size at the time in the area, it is reasonable to conclude that this is evidence of infraspecific combat or competition.
From the study’s abstract:
Trace marks on the bones of non-avian dinosaurs may relate to feeding by large carnivores or as a result of combat. Here the cranium and mandible of a specimen of Daspletosaurus are described that show numerous premortem injuries with evidence of healing and these are inferred to relate primarily to intraspecific combat. In addition, postmortem damage to the mandible is indicative of late stage carcass consumption and the taphonomic context suggests that this was scavenging. These postmortem bites were delivered by a large bodied tyrannosaurid theropod and may have been a second Daspletosaurus, and thus this would be an additional record of tyrannosaurid cannibalism.
I contacted lead study author Dave Hone with a few questions and he was kind enough to give me answers.
I asked him if he had any guess as to the sex of this individual. While it is possible to sex some dinosaurs, he told me that this was not possible in this case.
I asked Dr. Hone to comment further on the suggestions that the most likely species to have inflicted the pre-mortum wounds was another Daspletosaurus, even though another similar dinosaur, Gorgosaurus, was around at the time. He told me, “We favour Daspleto for the premortem as we think (and based on previous papers) this is a more likely case with more intra than interspecifc aggression leading to these kinds of interactions,” similar to what we see in modern animals that exhibit this behavior. I also wondered if the size of the teeth could indicate the size of the offending beast, and thus confirm the species. He told me they did not look at this too closely because there are various problems with that approach. “We did look at the patterns of tooth distribution briefly but between different sizes of animals (juveniles vs adults) different sizes of teeth within the jaws (front vs back) and then things like missing teeth etc. there’s no way of separating them out. There’s just way too many variables and they are only leaving limited marks. It’s mostly hard to tell even very different animals apart from bite marks let alone two similar and close relatives like this.”
I asked how common Daspletosaurus is in the fossil record and if this was one of the more common tyrannosaurids. He told me that “Actually it’s not that common. The Albertan Tyrannosaurs are generally pretty common but we do for example have more Gorgosaurus and Albertosaurus than Daspleto,” though Daspletosaurus is well represented.
Daspletosaurus is distinct in part because of various extra bony bits in the face and around the eyes, which could be for any of a number of functions. I asked if it is possible that Daspletosaurus was more involved with usually-but-not-always non-lethal infraspecific combat than other tyrannosaurids, if these features are related to what might have been extra protection (or signaling features that might arise from sexual selection). If so, would this indicate something about social structure? He told me, “I’m very wary of making these kinds of extrapolations as some things that look like certain classic signals turn out not to be. My personal opinion is that these hornlets in various Tyrannosaurs likely did function in sociosexual signaling (at the very least I suspect they wouldn’t do much to protect the eyes since that would be tricky place to bite) but it’s hard to say much. Sociality is misleading here as some things can be very social and fight lots and others almost never and vice versa for solitary animals.”
I also wondered about how infraspecific combat square with the individual being relatively young. Would this imply it was fighting off adults intent on cannibalism? Or, were juveniles fighting it out like hyenas do (new born hyena males from the same litter engage in deadly combat)? Or fighting over food? Or engaged in ritual fighting behavior that precedes, as preparation/practice, adult fighting behavior? I wondered if this would say anything about life history development of behaviors in this dinosaur. Dr Hone told me that “it is really hard to say. This isn’t an adult, but then nor is it really a juvenile. We know that some dinosaurs at least can reproduce before they are fully grown (so they are sexually mature when they are not osteologically mature – actually rather like humans, though obviously rather unlike most mammals, and certainly birds). So things get complex fast. This animals was certainly old enough to have been fully independent (though of course they may or may not have been gregarious / social etc.). I doubt cannibalism was normal, I’m sure there were the odd fights that resulted in deaths or adults killed the odd small juvenile (just like crocs do) but it’s a rare behaviour to go after other big carnivores for food – they are rare and dangerous, so stick to baby herbivores. After that it gets even harder so I’d prefer not to speculate too much, though I’d guess that IF solitary, smaller individuals would probably not be holding territories, since they are not big enough to defend them, and obviously immature animals would not be competing for mates or breeding sites or IF in a group to be an alpha of some kind (though that’s not to rule out some aggression to maintain even a lower rank), but it’s not much to go on – just too many unknowns.
What we need, obviously, is some way to bring these creatures back to life so we can observe them alive!
Caption for the figure at the top of the post: Figure 1: Skull in right lateral view showing numerous injuries indicated with black arrows and the relevant code letter (see the text for details).
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Interesting. One question (I probably should know the answer, but don’t):
What are the estimates for lifespan for Tyrannosaurs? For sauropods?
Or is that too broad a question?
How can this be proven scientifically? The bones in the soil could have undergone several changes.
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Was the Daspletosaurus a creature that stayed alone and maybe encountered other dinosaurs of the same species and fought with them? Or did this species stay together in herds?
If some dinosaurs reach reproductive capability before osteological maturity maybe the wounds were inflicted in combat over a mate by an older, more capable opponent.
If the extra bony parts on the face served a sexual display purpose, maybe the other Daspletosaurus was trying to damage them to make the juvenile seem less attractive (like male sharp-tailed grouse (Tympanuchus phasianellus) trying to damage each other’s yellow feathers).
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One can imagine a younger male Daspleto attempting some sexual poaching in the harem of a larger male and barely escaping an encounter with the “herd bull” tyrannosaur, lucky to get away with just some facial bites.
Or was the specimen a female? Could Daspletosaurus have been given to the kind of rough sex seen in sharks, wherein females frequently receive bite injuries?
the juvenile Daspletosaurus was well preserved. Many of the bones were present but how was their position in relation with the anatomical location?Why were there missing bones because erosion seems not an answer to me. the marks on some of the bones that indicate post-death scavenging. But, how do we know that most of the teeth marks are of the kind one would expect if a theropod dinosaur was biting it, for it shares its dental formula with many.
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I agree that there needs to be more research and it needs to be proven. Love the ideas about them beating each other up over a girl though! Do you really think the damage could go beyond just the flesh though and do actual bone damage?
Would it be possible that the bite marks were actually much smaller than they appear. Perhaps the grooves made by the teeth were eroded by the sand over time and in so doing, increasing the size of the bite mark?
Dinosaurs, such fascinating creatures!
As much as the information provided about these injuries is very convincing. I still find it difficult to agree that we can assume how they happened and who inflicted them on the Daspletosaurus. There are so many possibilities as to how the dinosaurs could have been injured, for example it could have suffered a server fall in its lifetime.
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Wow,this is fascinating but since this is science how true is this statement because the dinosaurs could have been tramped while on the soil decomposing resulting to alterations on the facial shape.
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Can this be proven scientifically? The bones could have undergone several changes in the soil over the massive time period.
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I would suggest that if daspletosaurus occurred in herds or packs and because of the fact that they were carnivorous, they will have bite marks on their heads because of the competition that occurs in their feeding frenzies.
The theories that came up are really fascinating.! I agree that the most logical seems to be Dinosaurs of the same species fighting over food or a mate. However, what possibilities might there be if this dinosaur was a female?
Folks almost all of these questions are answered or at least addressed in the paper, which is published in a journal with free public access. It’s not terribly long and Greg posted a link to it.
The theories considered are really fascinating. The most logical one’s seem to be the dinosaurs of similar species fighting over food or a suitable mate. However, if this dinosaur was female, would the possibilities also have been food fights, or territorial struggles, or would environmental factors have played a bigger role?
Astounding Theories!
Just to be out of topic for a bit,the skeletal arrangement of ancient dinosaurs I understand how they must have discovered it.But for conclusion on how they roared,I find it difficult to perceive how one discovered how this organism sounded since there was no trace of humankind at that time.
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My question how one can bring back these creatures to live? and Out of all possibility why do you really think that these dinosaurs were biting each other because there are possibilities that they were injured by other things?
wow. i am normally not fascinated by any facts about dinosaurs, but this has clearly caught my attention. is the bite marks representing territory? or maybe mate marks? or is it a simple fight between two high tempered males? (15079059)
The fight for food poses as a logical theory considering that this competitive behaviour can be witnessed in present day (15090478)
Since we do not know much about these ancient creatures we can not really determine why this species are doing this and what their true intention is. We can only assume these things.
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Interesting theories on what caused the conflict between the dinosaurs .The theory on dinosaurs fighting over their mates is quite fascinating but there is the possibility of the bite marks being caused because of competition for food and their territories. According to Charles Darwin and his theory of Natural Selection , competition between the species is normal. I noticed that you did mention inter-specific and intra-specific competition and I agree.
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I totally agree with you Shayuri
It’s true what he said about how the only way we will know for sure what caused the bite marks is for us to observe live speciments and their behavior in their prehistoric habitat…
Sadly that’s not possible so I think the next best guess could be made by observing present reptile species with similar marks on the face
In order to get the best understanding of the behavioral patterns of dinosaurs under circumstances , we need to study the behavior of modern day reptiles. Further we can study fossils, but the evidence may not be precisely accurate. Unfortunately we will never truly know the exact behavioral patterns and day to day lifestyle of these dinosaurs .
If the damage did manage to penetrate through the flesh and damage the bone of the dinosaur then the dinosaur would have surely had enough damage after the fight to die of its wounds. But scavenging is still a possible answer to the bite marks.
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Did dinosaurs not die out before early hominids came to existance? If so, how could they have ‘butchered’ them for food ,seeing as this is one of the explanations for the marks on the bones?
Did dinosaurs not die out before early hominids came to existance? If so, how could they have ‘butchered’ them for food ,seeing as this is one of the explanations for the marks on the bones?
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Did dinosaurs not die out before early hominids came to existance? If so, how could they have ‘butchered’ them for food ,seeing as this is one of the explanations for the marks on the bones?
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It has been very long since the last dinosaur so how can we know for sure that these bones belong to these creatures?
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can we prove this using science? because some of the thing cannot be proven scientifically
This article is extremely interesting; it is fascinating how much we seem to know about these ancient creatures. I wonder how much of this knowledge is still out there waiting to be discovered? And how much of this information is fact or assumption?
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If they are from the same specie, why would they eat each other? The theory is quite amazing nonetheless
If they are from the same specie, why would they eat each other? The theory is quite amazing nonetheless
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These bones are from a very long time ago, how do we know for sure the bite marks are from other dinosaurs or caused by the wearing of the bones
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The world’s oldest stone tools were found in Kenya. These tools are dated to 3.3 million years ago. According to this blog the Daspletosaurus lived approximately 74-77 million years ago, thus making the possibility of the damage to the skull, due to stone tools, highly unlikely. From present day knowledge we can conclude that dinosaurs were mostly aggressive, territorial animals. Therefore the marks on the fossil are most likely due to a power struggle, where two of the same species were battling over territory. If the sex of this specific case could be identified as a male, it would make this possibility even bigger.
Sources:
http://news.sciencemag.org/africa/2015/04/world-s-oldest-stone-tools-discovered-kenya#
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I have a question: Why are the holes in the dinosaur’s skull so small compared to the size of the teeth of the dinosaur that is bitten? Or could it be that a tiny dinosaur have bitten this big dinosaur after it died?
Informative, but is this not a common behaviour in animals, especially when researching the same species. Fighting for dominance and food in some species is the order of the day and face biting and facial damage do occur during such altercations. Just a pity that such magnificent animals such as dinosaurs cannot be studied live anymore!
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its bing long time without dinosaurs in this world it has been 365million years without them so how do we know that this bne belong to dinosaurs and if it is bone of dinosaurs how do we that the are fighting for food 15198309
I agree mentioned that probably the dinosaurs under went some sort of changes since they were just fossils. This is so new to me and fascinating.
Dinosaur behavior is difficult for paleontologists to study since much of paleontology is dependent solely on the physical remains of ancient life. So how much evidence do they have do you have that shows that this dinosaurs were biting each other.
Dinosaur behavior is difficult for paleontologists to study since much of paleontology is dependent solely on the physical remains of ancient life. So how much evidence do they have do you have that shows that this dinosaurs were biting each other 12288269.
Reptiles are derivatives of dinosaurs. Studying the pattern of modern day reptiles could give us insight as to how dinosaurs behaved. Even though stone tools were only created millions of years after people from the stone ages could still be responsible for skull damage.
Reptiles are derivatives of dinosaurs. Studying the pattern of modern day reptiles could give us insight as to how dinosaurs behaved. Even though stone tools were only created millions of years after, people from the stone ages could still be responsible for skull damage. (15106277)
The Dasplestosaurus had extra cadaverous bits on it’s face and nasal bones on the top of its head blended for strength. I just assumed since its built in such a manner it was only inevitable for that particular dinosaur to meet it’s maker. I mean with that structure it ‘allows’ it to be aggressive and cheeky
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I also wanted to ask did these beasts hunt in packs or just meet to feast on prey
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I wanted to ask did these large beasts hunt in packs or meet up together to feast on a prey
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I wanted to ask if these giants beasts hunted in packs or only came together to feed on a prey
i wanted to ask did these giant beasts hunt in packs or did they only come together when they went to feed
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I Totally agree with Angela, how is it that we make such assumptions regarding this, cannot we just assume that they were playing in a hostile manner
i completely agree with Angela, why assume such. why cant we just assume that it could be them playing in a hostile manner
its not like they were driven by starvation there was enough food at the time, why settle for cannibalsim
the dinosaurs of similar species fighting over, would the possibilities also have been food fights, or territorial struggles, or would environmental factors have played a bigger role?
Very interesting to see that even millions of years ago animals had some of the same behavior that animals nowadays. It’s amazing how science has advanced so people are able to determine these things. Just sad that we can’t determine exactly what the cause for these marks are and that we have to speculate.
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I found this very interesting. I am really fascinated by dinosaurs. Could this behaviour be similar to animals like the Bison for example? In combat for territorial possession and mates?
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Even though paleontologist have a lot of research to do, I like the fact that they give new information on the discoveries. 15202829
This article provides some insight into the behaviour of dinosaurs and possible theories as to how bite marks were found on the head of the juvenile Daspletosaurus. However, there is much speculation regarding the marks and what could have caused them.
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Interesting that they can tell whether injuries were made before or after death according to the bones
I find this article very interesting especially the fact that technology has become so advanced that we can now make these kind of assumptions scientifically. I do wonder though if it is completely accurate since there was no evidence considering the possibility of erosion on the skeletal impurities . Could it have been effected by erosion and possibly give a different assumed outcome?
I find this article very interesting especially the fact that technology has become so advanced that we can now make these kind of assumptions scientifically. I do wonder though if it is completely accurate since there was no evidence considering the possibility of erosion on the skeletal impurities . Could it have been effected by erosion and possibly give a different assumed outcome?
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This is really very fascinating. It so amazing how they can determine whether the marks on the bone were made pre or post-mortem just by looking at the fact that there was a certain degree of healing. Where these marks also found on other dinosaur bones or was it just this one?
Modern male birds partake in mating rituals consisting of aerial and plumage displays and dances – there are very few instances of direct physical confrontation or pitched battle for mating rights. This is characteristic across almost all genii and is not restricted by diet. This in turn implies that the size and proximity may play a role in encouraging direct physical confrontation for mating rights.
I wonder how they new that it was caused by oter dinosaurs
Dinosaurs roamed the planet before early hominids were around so how could they be responsible for the marks on the bones? The fight for food or territory between dinosaurs would be a more likely explanation for the marks found on the bones.
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It is amazing to read this but it never came into my mind to think that dinosaurs where able to bite one another.
It is amazing to read about this and who thought dinosaurs used to bite one another?