Posts Tagged 'tyrannosaurs'

Combat and cannibalism in tyrannosaurs

skull lat7_nIn recent years, it has become clear that at least some large theropods (and notably tyrannosaurs) engaged in some form of intraspecific conflict that can be identified by the numerous injuries inflicted on various skulls. Unlike predation attempts which would expect to strike to areas like the hindlimbs and tail, these are very localised to the face and imply animals stood head-to-head or side-by-side while doing this. Furthermore, at least a couple of records suggest cannibalism of conspecifics and this too has been seen in tyrannosaurs. Wading in myself, I have new paper out with Darren Tanke which describes a series of injuries to what is a fairly battered Daspeltosaurus skull that gives support to both of these areas, since it has both pre- and post-mortem bites on it from other tyrannosaurs.

First off, I must thank a number of people for getting this research to happen at all. The project started while I was unemployed and obviously short of research funding. My trip to Canada to examine the material was supported by a crowd-sourced campaign run through Experiment.com. Numerous people at Experiment and huge numbers of friends and colleagues contributed (and I’m sure, plenty of regular Musings readers) and they need my thanks. First among equals was the palaeoart community with Julius Csotonyi, Luis Rey and especially Brett Booth donating artwork or sales to support the work, but many people are gratefully acknowledged. Don Henderson put me up while I was in Canada, and Darren Tanke obviously invited me to write up the specimen. While naturally a lot of work has gone into this paper, the essentials of the marks and interpretations were things Darren himself had identified years ago so much credit needs to go his way there too.

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Right, onto the paper. It’s freely available through PeerJ and with 17 figures, so there should be more than enough info there for those who want to delve into the details, and thus I’ll try to keep things relatively brief here. The specimen is of something close to a sub-adult animal and there were plenty of the bones in the quarry (importantly these are in superb condition and there’s basically no evidence of transport or wear). There are numerous injuries across the skull (though absent elsewhere) and these consist primarily of healed injuries on the cranium. Not all of these can be directly attributed to bites, and some could have come from a number of sources.

However, a few healed marks can be interpreted as bites. There are some circular marks and punctures on various locations (including on the snout) and damage to bones that appear to represent some heavy impacts (deviated bones, pieces that have broken off and then fused back to the bone slightly out of position) and the like. Quite incredibly, both sides of the occipital region show some serious damage. On the left a piece appears to have been entirely removed (there’s healing round the remaining edge) and on the right, there’s a healed but circular puncture through the bone. In short, at least one and probably two separate bites came in to the back of the skull and snapped through the bones, though the animal survived and the injuries healed.

occiThis animal, despite not even having reached adulthood, clearly got into at least one big dustup and I would imagine, probably several, to have got so many hits to the head. Although there are a number of theropods showing injuries to the head that are interpreted as coming from other conspecifics, this is more extensive and serious than I’ve seen before. As to assigning it to a conspecific, this is tricky as there are other large tyrannosaurs in the formation (Gorgosaurus) and though these animals might well have come into conflict with one another, one can expect that conspecifics would likely come into contact more often (competition for similar niches, living in more similar habitats or direct interactions from being in groups perhaps). Thus it’s reasonable to infer this was a more likely source of such injuries.

Even so, the post-mortem damage is perhaps more interesting still. There’s one series of score marks along the inside and rear of the right dentary that well match similar bite marks from large theropods. A piece of bone has also broken off between two alveoli and been jammed down in between them and the score marks are coincident with some damage to other parts of the posterior mandible, so it looks a lot like there was a big bite here that took apart the back of the jaw. Given the position of this and the lack of healing, it’s reasonable to infer this as being post-mortem, but things get more interesting when you look at the taphonomy.

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When discovered, the dentary was more anterior than would be expected if the specimen had decayed in situ (the skull was lying with the palate uppermost). However, a number of dentary teeth (including those that must have come from the missing right dentary) were lying in the palate below where they should have been if the dentaries were in a natural position. Given the lack of evidence for fluvial action generally, this implies that the jaws were originally in place, decayed sufficiently to shed their teeth, and then the dentaries were moved. One has vanished and the other is in a more anterior position than if the specimen had simply decayed in situ (and the teeth have been dragged along somehow). It’s hard to imagine the tooth ligaments coming apart within hours of death, and the lack of bites to other parts of the specimen that would have been a more obvious target for feeding suggest this was probably scavenging.

This may or may not have been cannibalistic as it is not possible to tell apart Gorgosaurus from Daspletosaurus based on the bite marks alone. Still, it is very much a record of a scavenging interaction between two large tyrannosaurs and that is a nice addition to the available information on interactions between large theropods. Getting an idea of how these kinds of things worked in past environments really is a case of building up data from the rare occasions when such interactions are preserved, so while interesting in its own right, this really does help produce a more rounded picture of interactions between large carnivores both before and after their deaths.

 

Hone, D.W.E., & Tanke, D.H. 2015. Pre- and postmortem tyrannosaurid bite marks on the remains of Daspletosaurus (Tyrannosaurinae: Theropoda) from Dinosaur Provincial Park, Alberta, Canada. PeerJ, 3 e885.

 

Finally, while I’m talking about crowdfunding stuff, do check out David Orr’s appeal for his kids book on palaeontology. David designed the snazzy logo that I used for this project as modeled by myself and Darren above, so you can see how good his stuff is. Oh yes, and here’s an interview with myself and Darren Tanke on the new paper.

Near perfection with Gorgosaurus

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This is the famous Gorgosaurus specimen at the Tyrrell that is pretty much perfection when it comes to tyrannosaurs. It’s as complete a skeleton as you are every likely to see, in wonderful condition, articulated pretty much perfectly and in an iconic posture. I loved simply looking at it, and it’s a hell of a thing.

I did not however love taking a photo of it, the position it has been put it, combined with the lighting in the hall makes it extremely hard to photograph. Now while museums can’t cater to the requirements or demands of every single visitor (some want it light, some dark, some want things high up, others low down, some want chairs, some want spaces etc.) it is frustrating that what is possibly their best specimen on display is annoyingly hard to photograph and hence this single decent shot which really doesn’t show off the feet properly, or indeed the complete (yes, actually really complete) tail.

Even so, it’s a magnificent specimen and I think the photo does it a decent amount of justice and at least lets you see the real quality of the preservation and indeed the preparation to get it out like this. Enjoy.

Extra final bonus Gorgosaurus preparation post

Well, it has been a while since the last post where we finally rounded up and summarised Darren’s massive series of posts on preparing a Gorgosaurus specimen. Here Darren summarises the prep work done since and provides new photos of the skull now seen from the others side.

After a long hiatus, I update the Gorgosaurus preparation series, with this, the final installment. Since the last posting, the entire specimen, and select parts thereof were moulded in a high-quality silicone rubber compound so detailed casts of the specimen can be made in the future. After the moulds were removed, the entire specimen was covered in a separating layer of wet tissue paper, and then plastered over and flipped over.

The side now facing up is that which faced up in the field. As this is the upward-facing side, and there was only low rock overburden in the field, this side of the skeleton was more exposed to the effects of rain, frost, rock fracturing and rock expansion/contraction from summer heat (up to +40C) and cold winter temperatures (down to – 40C). Because of this, this side of the specimen is less well preserved, in fact I’d say in many places it is poorly preserved- in some areas the bone is like the consistency compressed hot chocolate powder. Bones are also badly crushed in many places. If I can remove the equivalent of a sugar-cube sized piece of rock per day, that is pretty good going as I super detail the many bones preserved. The skull, being better ossified, was in better shape, but the bone quite splintery in places. This means the work has proceeded very, very slowly. The tools and techniques were much the same as in earlier postings, though much of the work is being done with a head-mounted magnifying lens and later, probably microscope work. Also the work has to go much slowly. It can be seen that the posterior right side of the face is missing. This is because as the carcass rotted, the side of the head, exposed to water currents, was disarticulated and piece by piece the bones were washed away. We have a couple of them, but are missing 6-7 to make a full skull. However, we get a beautiful side view of the braincase which is important for researchers. We had the whole skull CT scanned recently and really nice images resulted for study by one of the Royal Tyrrell Museum scientists.

Preparation work on this side has also revealed some anatomical details that are important to future scientific study and eventual publication(s) that cannot be shared here or at this time and therefore, this series must end with this posting. I have been happy to share the preparation of this gorgeous little specimen with you all and hope you learned something about the intricacies of fossil preparation.

Best, Darren Tanke, Senior Technician II, Royal Tyrrell Museum, Drumheller, Alberta, Canada.

As usual all images are copyright to Darren / the Tyrrell Museum.

Guanlong

This is the skull of the Middle Jurassic tyrannosauroid Guanlong, the crested dragon. Or more specifically it’s the skull of the referred specimen, a near complete juvenile animal that’s in nearly as good condition as the adult. One thing it lacks though is the famous crest of the genus. While this could be put down to ontogeny, a look at the skull in dorsal view shows obvious signs of damage and there was most likely some form of crest here originally, though probably rather less well developed than the adult.

Carnegie Tyrannosaurus pt 2: a second adult rex

In yesterday’s post I was deliberately using photos that showed off the holotype Tyrannosaurus alone. However, the exhibit has a second, adult rex, mounted with the first. The two are challenging each other over the dead hadrosaur in a wonderfully dramatic and evocative pose. This great, not just because it’s so evocative – two huge carnivores facing off, but simply because there are tow of them. I suspect the average museum patron tends to think of a given skeleton as the species almost, so having a pair, with some (admittedly subtle) differences, shows that there are multiple specimens, with all the differences that come in a  natural population. Of course it also allows them to have different poses, suggesting ranges of motion and capabilities. All probably lost on most, but the kind of thing that can make people think, or will be remember another time, and simply great to see if nothing else. After all, this is a major expenditure to put up a second large mount for a species that is already represented (and that’s the type!). Great stuff.



Carnegie Tyrannosaurus pt 1

Yes this is only part 1 because there is quite simply so much Carnegie Tyrannosaurus material on display to cover. And here’s the first and most important – the holotype of T. rex, what is, in effect the very definition of what Tyrannosaurus actually is. It’s a superb mount and sits over the carcass of an Edmontosaurus and with the head rather dipped which makes it easy to get to see this up close which is nice. Three more posts to come, so stay tuned.

Guest Post: Love the Tyrant, Not the Hype

Tom and, shock!, *not* Tyrannosaurus....

Today Tom Holtz brings his piece to the table. Well, I say piece, Tom has promised me three (though he also originally promised to do a guest post about 2 1/2 years ago…) and this is a pretty big first one. Although he’s not a blogger, Tom is renowned for spending a lot of time online and handling questions from the public and getting involved in debates, so he’s very active on the outreach side of things. His recent dinosaur book featuring Luis Rey’s art really is an instant classic (and Tom maintains a great online species list for this). Anyone who knows Tom’s work knows about his fondness and affiliation for tyrannosaurs, so having just covered this little critter, it’s great timing for him to dive into tyrannosaurs for us:

Continue reading ‘Guest Post: Love the Tyrant, Not the Hype’

Raptorex

I am quite sure that this is something people have really been waiting to see following the controversy over the material, and certainly it seems to have been the subject of much discussion on the web as well as between palaeontologists. I’m not going to wade into that here, not least when I’ve been told there’s at least one more manuscript in preparation about this and it’s ontogenetic status etc. and I don’t want to interfere with or jeopardise anyone’s work with my thoughts. But the thing was on public display so a few photos seem in order. Suffice to say though, it looks pretty young to me, though I could only see it in a display case and not all of the material was there (the skull was represented by just a cast for example).

Anyway, here are some photos of the beast and there’ll be a bit more tomorrow too. These piccies are a combination of the mounted cast, and the combined holotype-cast in the display cast so the lighting, angles and elements vary a lot between photos.

Tiny Tarbosaurus

By now I’m sure most readers will have picked up on the new paper describing the skull of a tiny Tarbosaurus. It’s estimated to have been just 2 years old when it died and was around 2 m in length – that’s rather smaller than the 10-12m long adults! A few images of this hit the news when the specimen was first announced around three years ago and can be hunted down if you look. There is one above of me with a cast of the specimen as it was when discovered (it’s now been fully prepared out) which gives you a pretty good idea of just how small it was.

While above is just the cast, I was lucky enough to see some of the material while it was undergoing preparation. Even better I was allowed to take some pictures for my own research and have been told I can show off a couple of them here now that the paper is finally out. My thanks for this to Mahito Watabe and his team for this generosity. Though perhaps inevitably with Larry Witmer on the team, there are even better pictures and 3D animated scans of the skull out there too!

This is post is (a little) more than just a couple of photos though as the paper itself has some interesting things to say about tyrannosaur ontogeny. This is the smallest / youngest tyrannosaur we have and coming from an especially big genus makes the size discrepancy even greater. This is pretty handy as there are a variety of problematic tyrannosaurs specimens out there that may or may not represent distinct taxa but being known only from juveniles make this hard to work out. However, if you have a really good handle on how some characters do (or do not) change as individuals get older and bigger then you know what you can and cannot rely on when looking for unique characters in other juveniles.

For me the most interesting characteristic was that of the number of teeth. While there is a little intraspecific variation in tooth numbers, there are also some discreet differences between taxa too – the big tyrannosaurines like Tarbosaurs and Tyrannosaurus have fewer teeth than do smaller ones like Daspletosaurs or Alioramus. In the past it’s been suggested that this number actually changed during ontogeny with the number starting relatively high and the number of teeth reducing as the animal got bigger. However this little guy has exactly the same number of teeth as an adult Tarbosaurus. While this doesn’t exactly disprove the hypothesis, it does at least show that at best it’s not always true, and so a smaller tyrannosaurine skull with lots of teeth could grow into a big adult with lots too.

All in all a very revealing paper (and superbly illustrated I should add) and with more to come on the postcranium, this is going to be an important specimen for many a long year. Sadly, it’s parent institution may not be able to say the same as I will talk about tomorrow.

OK, so I’m just milking it now – final Zhuchengtyrannus roundup

Yeah, this is still creeping along. I’m trying to stop honest and while I’m sure I’ve lost most people by now, this is more or less the end of it. (More or less because there are ZT related things to come but which won’t actually really mention the damned beast itself so from here you’re basically safe). This has, understandably, been a hectic week and I’ve still got bits of work to do related to this so I’m not quite done, even if the blog is.

Going all the way back to the Eeeek! post, I want to again thank people for being helpful and not jumping me with ZT appearing all over the web before we were ready. It is much appreciated and helped us get maximum impact with the media. On that note, I’ve yet to put up this link to the University College Dublin page where there are links to a great many of the online media about Zhuchengtyrannus including a video of me talking about it. If you’re not interested in hearing me say things you’ve already heard or read 50 times over on here then you can try and identify all the various dinosaur and pterosaur books on the shelf behind me. Fun for all the family (possibly).

And while I’m here, here’s links to all the previous posts on here introducing this guy, notes on the taxonomy, ecology, size, and artwork. And if really like this, go do a Google image search for ‘Zhuchengtyrannus’, it’s quite startling.

 

So just how big was Zhuchengtyrannus?

After all these posts, I’d understand if you were sick of this thing by now, but there is still (sadly for you) some more to discuss. One thing that has been left untreated until now on the blog is the size of Zhuchengtyrannus. Knowing the media would immediately want to know*, we did suggest that this was an 11 m long, 4 m tall and 6 ton animal, but really, how accurate are these? And where does that place it among other theropods?

*Indeed, despite including this in our press pack, I was still regularly asked about this, and was asked for ‘real life’ examples as well.

Well first off the easy stuff – we can measure the bones we do have and that gives us a 64 cm maxilla and a 78 cm dentary, though the latter would probably have been a bit longer in life. These obviously make up a significant part of the skull, but it would have been much longer when complete. As noted before, tyrannosaurines are generally pretty conservative so we can compare the sizes of these bones to their equivalents in other specimens for comparison. There are two adult Tryannosaurus specimens with maxillae just 1 and 2 cm longer than that of ZT with one having a bigger and the other a smaller dentary, so it’s immediately fair to call this about T. rex sized. However, the specimen known as ‘Sue’ is a real monster of a rex with a maxilla some 79 cm long, which is a fair bit bigger bigger. There are several Tarbosaurus specimens in the low 60s for maxilla length, with one (I can only imagine is a juvenile) at 49 and a pretty big one at 73. Several other more basal tyrannosaurid and tyrannosaurine taxa get close, but are not quite as big as ZT.

Obviously we just have one specimen and it’s impossible to know if it was a big or small or very average specimen. Assuming the latter, it’s very slightly bigger than most specimens of Tarbosaurus and slightly smaller than most Tyrannosaurus ones. That means it’s basically about the same size as these two, and lying in between on average.

From that of course we take our other estimates of size – while Sue is about 13m long, the others are more like 11 and so in the paper we suggest that ZT was between 10 and 12 m long (or more simply, 11 m to the press). In hindsight the 4m tall might be a bit much, but not by a huge amount, and as ever with measures like this, vary a lot with what the animal is or could do. If it stretched or tilted the head up (OK, perhaps straw grasping a bit) it would probably be over 4. So onto the mass, which is inevitably the most contentious, if only because it’s the hardest to determine.

Long time readers will be aware of the huge range of masses that have been posited for all manner of dinosaurs over the years. While the ranges have been narrowing and the values converging there is still quite a lot of disagreement. Add to that the natural levels of variation between individuals and even the fluctuations of individuals (sometimes they’re fat, other times, thin) and it should be obvious that even if our calculations were 100% accurate, you would still need a range of figures for a given species and even a single individual. For an animal this size that could easily mean that a single specimen could vary by as much as a few hundred kilos and as a species perhaps the biggest and smallest were well over a ton apart or even two. As such any reasonable number is going to be ‘about’ right and with estimates for T.rex typically being around 6 tons (though up to 8 have been suggested) then 6 is a perfectly reasonable number for ZT, and though we really are extrapolating from less than half a skull, the group as a whole is conservative enough that I’d be surprised if we were much out with any of these numbers.

So where does this put this critter in the pantheon of predatory theropods? Well obviously Tyrannosaurus is bigger and Tarbosaurus is pretty much the same. I don’t think anyone would argue that (in terms of length at least) that Spinosaurus, Giganotosaurus and Mapusaurus are not bigger (and here’s a good chance to link to this old image of mine). After that, well, I’m kinda out of bigger ones. While admittedly ZT is in the same position as some possible other rivals (i.e. we have enough o make a good guess but not enough to be certain) I don’t think it unreasonable to suggest that Zhuchengtyrannus sits in the all time top half dozen.

The ecological implications of Zhuchengtyrannus

OK, I admit there’s not actually too much to say about this, but what little there is, is quite important. Zhuchengtyrannus is really rather big – a little smaller than Tyrannosaurus, about the same size as Tarbosaurus and thus as a theropod perhaps bigger than anything except these two, Spinosaurus, Mapusaurus and Giganotosaurus (and more coming on that tomorrow). It was certainly a serious customer.

More boringly, in a way, Zhuchengtyrannus is really quite a normal large tyrannosaurine –the anatomical differences are sufficient for taxonomic purposes but would probably make no real difference to the overall appearance of the animal – that is, as far as we can tell it would look in life very much like Tarbosaurus and Tyrannosaurus. While there isn’t that much of it, what we have is quite normal and it’s reasonable to infer that this animal was occupying a similar niche to the other giant tyrannosaurines (and that means predation and scavenging).

That is in itself a bit of a novelty. As I’ve noted before when discussing spinosaurs, it’s actually quite common to find multiple, similarly-sized large theropods in the better-known dinosaurian faunas. We find Allosaurus, Torvosaurus and Ceratosaurus together, Sinraptor and Monolophosaurus, Charcarodontosaurus and Spinosaurs and so on. Even when it comes to tyrannosaurines we find the smaller Daspletosaurus and Albertosaurus together (not to mention our old favourite Gorgosaurus). However, Tyrannosaurus seems to have lived alone as it were (and you can argue Nanotyrannus, but it’s quite a bit smaller) and Tarbosaurus may not have been really troubled by Alioramus. While we have no direct evidence that Tarbosaurus and Zhuchengtyrannus overlapped directly their fossils are being recovered from very similar times and only a few hundred kilometers apart. It’s really quite likely that they met and of course ZT is itself accompanied by another large tyrannosaur from the same quarry so there could have been quite a party going down.

To employ a much overused phrase, this does rather leave T. rex as the exception that proves the rule – it’s increasingly looking like the only big theropod which doesn’t come with at least one accompanying near-equally sized alternate carnivorous theropod. Despite the ever increasing similarities between the Late Cretaceous faunas of North America and Asia, T. rex does still seem to be, in at least one way, still the undisputed king of his own backyard.


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