What can CT imaging reveal about dinosaur skulls?

If our hunt and excavation have been successful, we should now have a prime dinosaur specimen to examine. But given the age of some of these fossils, surely there’s only so much we can learn? Well, perhaps not. Thanks to advances in imaging techniques we can now look inside fossils without so much as lifting a chisel. These scans reveal the internal structures of creatures that lived hundreds of millions of years ago, offering insights we never thought possible. I went to Christ’s College, Cambridge to meet Annabel Hunt…

Annabel - So as part of my PhD research here at Cambridge, I've been examining a wide selection of different dinosaur fossils. So I've mostly been focusing on theropod dinosaurs, such as Velociraptor and the formidable T-Rex, which I'm sure many listeners, if not everyone, will be very familiar with. As well as these theropod dinosaurs, I've also been observing some sauropod dinosaurs, such as Diplodocus, and also some Ornithischian dinosaurs, such as Triceratops. I actually examine the skull specifically because I'm interested in looking at aspects of the brain case and looking at features of the brain case and comparing it across different dinosaur species.

Will - A brain case, even if it was alive today, sounds pretty brittle and pretty delicate. We're talking about brain cases that are hundreds of millions of years old. How do you possibly literally get inside the minds of that sort of thing?

Annabel - Exactly. So they're incredibly fragile. And I myself have actually examined some of these brain cases in person with a fossil. And I have to say, it's very scary actually trying to manipulate these. And this is where a technique called CT scanning really comes in, because it's a way that we can digitally visualise this brain case material, which means that you can examine it without the risk of breakage. So I'm sure you're all very familiar with what an X-ray looks like that's taken at a hospital. So you can imagine if an X-ray is taken of your hand, that represents a single cross-section taken through your hand. The white of the bone is really distinct against the black air that surrounds it. You can really clearly see that bone. Because I'm interested in studying the whole skull, it's no good to me if I just have a single cross-section, a single X-ray taken through a skull, is it? Because then that's just one cross-section. I'm not able to visualize the whole skull. So if you imagine that one X-ray taken of your hand, I'm going to take multiple X-rays through that dinosaur skull. What that allows me to do is to stack up all of those individual X-rays, and I can make the complete dinosaur skull, and I can recreate that in digital. So I can then examine and manipulate that dinosaur skull however I want to.

Will - So CTs offer a great resolution without having to break the fossil itself, which is always good. But in terms of you've now created this image, this file, that sounds like a lot easier to share among the wider fossil community.

Annabel - Yeah, definitely. This is one of the things that's fantastic actually about CT scanning is because once someone has done a CT scan, and you've kind of produced this replica of the skull essentially, it means then that that can be really easily shared with anyone around the world. So rather than someone who's interested, say in a T-Rex, having to travel all the way across the world to examine that specimen in person, it means you can literally just transfer the file to someone. So it's much better in terms of data availability, and it means you can get access to specimens from all around the world.

Will - And what have you found out now that you've had a poke around in a few dinosaur skulls? What have you found out about the internal structure?

Annabel - So essentially what we're seeing is that a particular feature of the brain case I'm really interested in is seeing how that shape is really variable actually, even within groups of dinosaurs that are quite similar to each other. So like say the dromaeosaur is like your velociraptor and other similar dinosaurs. But even though they're in that same group, there can be a lot of variation in this brain case structure. And that's something that I'm really interested in to work out kind of why that is, why there's so much variation within that level. And there's of course a lot of variation even across dinosaurs as well, and some similarities. These are all things that I'm very interested in working out why we're seeing that.

Will - If you were to speculate, why do you think there might be that variation? Different shaped brains do different things, I guess? Do you anticipate that this could be a response to a need to change in behaviour, or maybe a change in environment? Do you have any theories on that?

Annabel - I think it's quite likely that it is kind of functional. There's a reason why we're seeing these changes in shape. Maybe it could be related to different diets potentially. So I do think there's a functional reason for this variation we're seeing. And that's something that I'm really trying to work out why we're seeing that. And I think it's really exciting, kind of why we're seeing this. And I do think there's a functional reason, yes.

Will - CT scanning, I wouldn't want to downplay it at all, but it is almost commonplace now, as you say, in many medical settings, and it seems to be fairly commonplace in imaging settings as well. Are there any other interesting techs coming down the pipeline that you think are really going to revolutionise the way that we view fossil structures?

Annabel - I mean, I think for me, I mean, CT scanning, although like you say, it is very common, and like particularly with medical CT scanners, and some of the dinosaur scars I've looked at were scanned actually with medical CT scanners rather than specialist ones. And the funniest thing was when I opened up a scan, and it kind of said patient name as part of the files. That was quite funny to see. But I think what is good is that some places now are kind of having their own specialist CT scanners just really for scanning fossils, and these can scan at a higher resolution. So we can see more than we can see with these medical CT scanners. Synchrotron CT scanning is something that is very exciting for me to think that if that becomes, comes into more widespread use, that can reveal so much information about dinosaurs, dinosaur skulls and features of bones. And I think that's something for me, the more widespread usage of synchrotron scanning is something that really excites me.

Will - Yeah, it does sound like from what I've read synchrotron is almost like CT's bigger brother, is just able to absolutely power through with even stronger x-rays.

Annabel - Yeah, and you can find out so much more, or the resolution of things, you can see even smaller features that you wouldn't be able to see, which I think is, and to see bone texture in even more detail. So that's kind of exciting for studies focusing specifically on looking at how bone kind of grows in these dinosaurs and kind of looking like tree rings, essentially how dinosaurs can show their growth essentially in these distinct kind of bands. And I think it's just really exciting to see where this is going to go with improvements in technology.

Will - I guess as a final question, and this is pure speculation, but do you anticipate that our imaging ever gets so good that we could almost fill in the gaps of all that soft tissue? And if we could get a good enough idea of what a brain casing looked like, do you think we could ever anticipate working out what an actual dinosaur brain could look like?

Annabel - Yeah, so that's actually what's really interesting because some people actually do work with reconstructing dinosaur brains, okay. So this isn't something that I actually work with, but some people are doing that. They're able to kind of reconstruct this soft tissue based on the hard kind of bone material that surrounds it. So this is what's so fantastic. We can understand the hard bone anatomy in so much detail that people can then reconstruct the soft tissue. So people have been writing about what certain dinosaur brains would have looked like, which I think is incredibly cool.

Will - So Jurassic Park might not come from amber, it might come from a 3D printer instead.

Annabel - Maybe!