Dr Susie Maidment
Dr Susie Maidment is a palaeontologist and a researcher at the Imperial College London. She is a leading expert in Stegosaurus and its relatives. Her key research work involves using geology to solve paleobiological problems.
T. Rex is actually closer to us in time than it was to Stegosaurus.
On getting interested in science
Well, when I was about, I don’t know, probably five or six, my grandpa said to me, ‘What are you gonna do when you grow up?’ and at that point, you know, it was the real…I was really not sure between being an actress, of course, as every six year old girl is gonna be, or being a scientist and, ah, I went for scientist with some encouragement from my grandpa, and he said, ‘But what sort of scientist do you want to be?’ And, obviously, being six I was really into dinosaurs, so said I’d like to be a dinosaur scientist. And that’s been pretty much it ever since, so it made my career interviews very easy at school, all those decisions I had to make were very easy because I knew what I was gonna do since I was six, so, yeah.
Probably the first thing I did was…when I was doing A level geography I did a project in Charmouth on the Lyme Regis – Dorset coast – which is now the world heritage site, at the time it wasn’t – and I worked as a volunteer in the Charmouth Heritage Coast Centre there, just walking along the beach, helping kinds find fossils and showing them how to find little ammonites, you know the little curly snail like fossils, things like that, in the cliffs there, so that was probably my first job.
On the importance of palaeontology
Well it’s…when we look, when we think of ecology, you know, ecologists talk about what’s going on now, you know, how species are going extinct, rates of extinction, this kind of thing. You know, we’re looking at a really small time slice, we’re just looking at the time slice of what we have recorded, so maybe a hundred years or a couple of hundred years. We’re not able…and that’s only in the context of what the climate’s like at the moment, how the climate’s changed in that relatively short period of time, for example. We’re not…what paleo allows us to do is to go back many hundreds of millions of years in the past to times when the climate was very different, the continents were arranged very differently, um, to look at ecological structures there, to look at environments and we can just get a much, sort of, better perspective on how things work, how the environments work, how the climate system works, rather than just looking at this very narrow snapshot of the world at the moment, which is probably not really a great time to be looking at things like that because we are really in a mass extinction at the moment aren’t we, you know, lots of things are going extinct at the moment, so we’re probably not looking at the best time slice right now.
It allows us to look back in the past and get an idea of what things were like in the past, which can inform us about today’s world.
Yeah, I think…this is something I always find, it blows my mind when I say it, it always makes people go, ‘Wow, that’s amazing’, but the dinosaurs were around for a really long period of time, so they evolved about 235 million years ago and they went extinct 65 million years ago. So you typically see…you might think of the age of the dinosaurs and imagine all these dinosaurs kind of running around together and of course that’s not the case at all because they were around on earth for, you know, 200 million years, or a bit less than that, but the Stegosaurus for example, the dinosaur that I work on, was around about 150 million years ago, T. Rex was around 65 million years ago, so Stegosaurus was already a fossil by the time that T. Rex lived and T. Rex is actually closer to us in time than it was to Stegosaurus. So I think that really emphasises the length of time that we’re talking about and how long the dinosaurs were the dominant animals on this planet.
Yes, there were mammals around before the dinosaurs, actually, and during the dinosaurs, there were mammals, but they just weren’t the dominant…they were kind of small, they were maybe…the largest was about the size of a cat a far as we know, they just weren’t the dominant terrestrial vertebrate; that was, that niche was totally taken by the dinosaurs. And the extinction of the dinosaurs – or at the least the non-birds dinosaurs – perhaps created a vacant ecological place that allowed the mammals to then radiate into.
But just to put into perspective the amount of time were talking for that evolution to occur, we actually have a common ancestor with orangutans around about 12-15 million years ago. So, 65 million years is actually a really long time in evolutionary terms.
On studying Stegosaurus
Well Stegosaurus has always been my favourite dinosaur, when I was a kid I had a Stegosaurus money box and a blowup Stegosaurus and all that sort of thing. But, actually, quite often when you’re an undergraduate and you’re going forward and you’re doing a PhD you don’t get to choose your own topic, you don’t get to choose your own project and, um, that’s primarily because you don’t necessarily know what needs to be done in the area, you know, I was coming from being a geology student to going into palaeontology which was not an area that I was an expert in by any means. And my supervisor suggested to me, you know, would you like to look at the relationships between the stegosaurs because it’s an area that really needs to be sorted out, no one’s looked at it since the seventies, we haven’t applied any modern techniques to it. And I thought, stegosaurs, brilliant, yeah, ‘cause it’s my favourite dinosaur as well, so what a great coincidence.
That’s amazing because Stegosaurus is one of the most iconic dinosaurs, you know, you say to any seven year old child, ‘What’s Stegosaurus?’ and they’ll be able to describe you the plates on its back, but actually we know not that much about it at all. But there’s also a whole load of other stegosaurs, closely related animals to Stegosaurus but we don’t call them Stegosaurus, so there’s…I think there’s twelve different genera of stegosaur and my PhD was focused on working out the relationships between them. So nobody had really looked in a sort of modern context…had really looked at the way that all these dinosaurs were related: who evolved from whom or who was the most closely related to whom and so that was what my work was based on. But also, no one had really gone through the whole lot systematically and looked at their anatomy, looked at how they varied, how they differed from one another and things like that, so really it was their anatomy and their relationships that was the bulk of my work on them.
On the colour of dinosaurs
Well that’s a really interesting question because probably four or five years ago if you’d asked me, you know, do we know anything about colour in dinosaurs, I’d say no, we don’t and we never will. However, over the past five years, maybe particularly in the last three years, there’ve been a number of discoveries of very, very well preserved ‘dinobirds’, so these are the dinosaurs that are very closely related to the origin of birds, because birds are of course dinosaurs, and they have their feathers preserved, and so all of these dinosaurs have feathers. So feathers are not a unique characteristic of birds, they’re actually distributed in these meat eating dinosaurs that are related to birds. And what people have found in those feathers when you go down to a very microscopic scale are structures that, um, you can also see in modern day bird feathers that actually give the feathers their colour. And people have discovered that the different shapes of these structures code for different colours. And what they’ve been able to do is zoom into the fossils, find these structures and figure out what colour the feathers were which is really amazing, you know, to be able to do that on something that’s a 100 million years old – or 65 million years old even – is just incredible.
So they have successfully managed to identify black, white and red, I believe sort of greyish colours and also kind of iridescent-y black colour in a number of different dinobirds which have feathers. So far, to my knowledge, nobody’s been able to do this with just skin, so if the dinosaurs…things like the Stegosaurus, we have no evidence that they were covered in feathers, they might be quite strange to look at if they were covered in feathers, I don’t know, I can’t imagine a Stegosaur covered in feathers but, presumably they had scaly skin. In fact, we’ve got some preserved dinosaur skin with big scales on it, but nobody’s found the structures, to my knowledge nobody’s found the structures that code for colour in those so at the moment we don’t know what those colours would’ve been, so those collages that you’re talking about, those sort of drawings that you see [of dinosaurs] is a total guess.
On dinosaur extinction
I think it’s pretty much accepted by almost everybody that the straw that broke the camel’s back for the dinosaurs was the meteor. So this meteor hit the Earth just off the coast of Mexico, the Yucatan Peninsula, and it hit carbonate sediment which would’ve caused the sediments to sort of evaporate and then rain down acid…very acidic rain onto the Earth. It caused localised tsunamis, it would’ve caused probably a large ash cloud that would’ve encircled the Earth and may have covered the Earth for some time and blocked out a lot of sunlight so you lose your primary producers, your plants are unable to grow anymore because the sunlight’s been blocked out, so then your herbivores die, so then your carnivores die. And I guess that’s…almost everybody accepts that to be what killed the dinosaurs.
However, there is a debate about whether the dinosaurs were already in decline up to that point and it seems that the evidence suggests that the environment was probably quite stressed, there were lots of volcanic eruptions going on, there was probably already a lot of sort of noxious gases in the atmosphere so there was a large greenhouse effect and it seems like the number of dinosaurs, of individuals, was quite high, the number of species, so the diversity, was actually decreasing, or so some studies suggest. So it seems like the dinosaurs were kind of declining and then the meteor finished them off.
On creationists and dinosaurs
Yeah, I’ve done some digging, in Wyoming actually, both dinosaurs and also I was working as a research assistant for my friend who is digging fossil fish and we…where they find these fish is in a formation in the rocks called the Green River Formation: beautiful, beautifully preserved fish, mammals, plants, everything, wonderful place to dig. But they also quarry this stone as a sort of building stone, that you can have laid in your shower or your work surface kind of thing. And we were digging these fish in these commercial quarries and they…they quarry this by hand, and the guys that were working in these quarries were generally, um, poorly educated, relatively poorly educated, you know, not, um, as you say…Mormon, actually, most of them were Mormons. And we were sheltering from a thunderstorm one day and chatting with these guys and they were kind of a bit, they were like, why are these two girls here digging up in this quarry, what are they doing, why are they interested in these fish, so they were very interested in what we were doing. And so they said, right, you know, what are you doing, how did the fish get there, so we explained the fossilisation process, you know, they fell to the bottom of the lake, and then the sediments covered them and over millions of years they got compacted etc. etc. and the guy goes, ‘Huh, what about when the Earth was all covered in water?’ And I thought, wow, that’s really clever, he’s talking about the time when all the continents were a mass and there was one ocean and one continent, and then I thought, no, he’s not, he’s talking about the flood, he’s talking about Noah’s flood. And we got talking about God, and he said…and I think I said, well I don’t believe in God and his jaw just hit the floor and he said, ‘I have never heard anyone say that before’. And the quarry manager sort of was going [gesture to stop talking] to me and, yeah, it never occurred to me that that was something that you just don’t say in Wyoming, it’s just not done. So that was…that was kind of a big learning curve, I was like, right, we don’t express our religious beliefs round here then, OK.
On career highlights
I’ve been on some amazing digs where, in the Morrison Formation where we have…we dug up four Stegosauruses which was quite exciting, or four parts of Stegosauruses I should say, and one Sauropod, again, it’s probably Camarasaurus although I’m not sure it’s been officially, um, decided what that animal was yet. But when we were digging that, we were digging the neck and we were, yep, as I say, you get one neck bone out and you think, is there gonna be another one connected, and there was and there was and the neck was there and we got to the end of the neck and we’re like, where’s the skull, because the skull’s the really important bit and there’s hardly any of them known and it’s very fragile and usually falls apart, and we got to the end of the neck and we dug and we dug and there wasn’t a skull. And then we were all sitting around a clearing in the area and one of the volunteers said, ‘Huh, that looks kinda weird’, and I went over and had a look and it was the tooth row, the upper tooth, upper jaw and it was lying…and the skull was lying upside down with the jaw facing upwards and then we excavated round and found the whole skull so that was very exciting. So that was probably the highlight.
On the great remaining questions of paleontology
Oh, that’s a really difficult question. I think…oh, there are so many…I think probably colour would be a really interesting one, so what, you know, what are the colours of the dinosaurs that we don’t know. I think probably the origin of flight is something that’s really very interesting and quite a hot topic at the moment so, as I say, birds evolved from dinosaurs. Pinpointing that position where a dinosaur becomes a bird is proving increasingly difficult because all the features that we associate with birds keep turning up in dinosaurs. So where did dinosaurs stop and birds begin I guess is a big question, but also how did flight evolve, and there seems to be now some evidence that flight evolved on multiple occasions within dinosaurs, so there were flying dinosaurs as well as birds around at the same time. So that is an area that I think really needs to be, you know, it is being worked on actively and it is really exciting.