The Ancients - Stegosaurus: Titan of the Jurassic

Episode Date: December 14, 2025

Few dinosaurs are as instantly recognisable as the plated titan Stegosaurus - it's the Jurassic giant with a brain the size of a walnut and a tail that could kill.In this episode of The Ancients, Tristan Hughes is joined by Dr Susannah Maidment of London’s Natural History Museum to uncover the secrets of its incredible armour, explore the latest theories behind its bizarre anatomy, and journey back to the Jurassic World it dominated to understand how this unique giant truly lived and fought. Join us to dive into the latest research and discover the surprising truth behind one of prehistory’s most beloved dinosaurs.MORETyrannosaurus RexListen on AppleListen on SpotifyThe Rise of the DinosaursListen on AppleListen on Spotify Watch this episode on our NEW YouTube channel: @TheAncientsPodcastPresented by Tristan Hughes. Audio editor is Aidan Lonergan. The producer is Joseph Knight. The senior producer is Anne-Marie Luff.All music courtesy of Epidemic SoundsThe Ancients is a History Hit podcast.Sign up to History Hit for hundreds of hours of original documentaries, with a new release every week. Sign up at https://www.historyhit.com/subscribe. You can take part in our listener survey here:https://insights.historyhit.com/history-hit-podcast-always-on Hosted on Acast. See acast.com/privacy for more information.

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Just visit historyhit.com slash subscribe. Hello and welcome to our latest ancients episode. Today we're going to the time of the dinosaurs, but just before that, I wanted to do a quick shout-out because a couple of weeks ago, I got a message from one of our fellow ancients listeners, Hugo. And it was a video message, and it featured Hugo and the youngest listener of the ancients. Two-month-old Aurelia, Hugo and his wife's newborn daughter. Now, Hugo sent me a wonderful message to let me know about Aurelia and how she's already been delving deep into the ancients archive. Her favourite episodes already being the Permian extinction and the fall of the Sumerians.

So Hugo, well done. You've already got already hooked on global prehistoric catastrophes and the falls of civilisation. So keep it up. Anyways, on to today's episode, we're going back to the age of the dinosaurs to talk through the story of what is for many of us our favourite dinosaurs. than iconic, plated, armoured dinosaur Stegosaurus. And to talk through it all, we've got one of the leading experts on armoured dinosaurs, none other than Dr. Susanna Maidement from the Natural History Museum. Now, Susie, she came into our studio, so we filmed it as well.

You can watch it on the YouTube channel, also featuring a fluffy Stegasaurus toy. Steggy, it is my own, I must confess. And I really do hope you enjoy. Let's go. The Stegosaurus, one of paleontology's greatest icons. It was built like a tank, with hind legs like tree trunks, but its head held a brain no bigger than a walnut. It carried one of the most terrifying defensive weapons in history, in prehistory, four razor-sharp spikes swinging from a powerful tail, the legendary so-called Thagamizer.

Today we're delving deep into the world of Stegosaurus. We'll uncover the secrets of its incredible armour, explore the latest theories behind its bizarre anatomy, and journey back to the Jurassic to understand how this unique giant truly lived and fought. And I'm joined by the one and only Dr. Susie Maidman, paleontologist at London's Natural History Museum, which is home to Sophie, one of the most complete Stegosaurus fossil skeletons on display in Europe and indeed the world. Susie, it is great to have you on the show. Thanks very much for having me. It's pleasure to be here.

And we're talking about Stegosaurus today, and this feels like for so many people, it is their favourite dinosaur. It is iconic today. It absolutely is. And every seven-year-old knows what Stegosaurus is. And I give talks about Stegosaurus and I ask in the audience first, you know, who's heard of Stegasaurus? Because this talk's going to go badly if you don't know what I'm talking about, right? And, you know, almost everyone puts their hand up. Everyone knows what Stegosaurus is. I guess we're quite fortunate to be in the UK with the study of Stegasaurus

because we've got one of the best preserved specimens at the Natural History Museum. Is it Sophie? Yeah, we have the world's most complete Stegosaurus on display at the NHM. But actually, there are also two different species of Stegasaur known from the UK, including the first one ever discovered, which was found in Swindon. In Swindon. It was. The Swindon Stegasaurus.

The Swindon Stegasaurus. It's called Dacentreras, Armitas. It's one of my favourite dinosaurs, actually. It's on display also in the Natural History Museum, but it's in a kind of a cabinet, like a slab mount, and people just walk past it, they don't notice it, but it's the first stagosaur ever found anywhere in the world. Justice for the Swindon Stegasaurus, that needs to get more. So maybe we'll talk about it a bit more as this episode goes along. But I feel we need to address this first off. You mentioned the word Stegosaurs there. We've already said Stegosaurus. So can you tell us the difference between the two words? Yeah, so Stegosaurus is one type of stegasaur. Stegasors are a group of dinosaurs.

So it's a bit like having antelope as a kind of, you know, group of animals that kind of look the same, evolved from a common ancestor and are quite diverse today. But then there's individual species within that that you can recognise. And it's the same with stegasors. So we have a whole range of them. They lived all around the world. And of course, Stegosaurus is the one that everybody knows, but there are loads of others, actually. Does it have a particular scientific name?

It's Stegasaurus. Is it just stegosaurus? For most dinosaurs, we don't have kind of popular names. They are just the names that they're given. But, of course, our one at the Natural History Museum, Sophie, has a nickname. But, yeah, no, it's Stegosaurus, yeah. Well, we'll cover like Stegasaurus at large as well in this chat, because it feels like the others.

We can shine the spotlight on them at the same time. But when about in the age of dinosaurs do Stegasors live? Yeah, so they first evolved in the middle Jurassic. So that's about maybe 167 million years ago, something like that. And they really get going in the late Jurassic. So that's when they're most diverse and we know the most different types of stegasaur from. And then they really decline after that and actually go totally extinct by the end of the early Cretaceous about 100 million years ago. So what types of dinosaurs should we be imagining living alongside them?

Because sometimes you'll see pictures of a stegosaurus defending against a Tyrannosaurus rex or something like that. But that feels like a misnomer. Yeah, it's a really common misconception that all the dinosaurs were kind of, you know, mooching along together in the same ecosystem. and actually, of course, they weren't at all. I mean, aside from the fact they're living on different continents, although Stegosaurus and T-Rex did live on the same continent, they were actually separated in time by millions of years. So Stegosaurus was already a fossil when T-Rex lived.

T-Rex lived 66 million years ago. Stegosaurus lived 150 million years ago. So T-Rex is actually closer to us in time than it is to Stegasaurus. You stole the line. You stole the line exactly. I love that fact, the fact that T-Rex lives closer to us than Stegasaurus does. Okay, well, you mentioned location in the world. where do Stegosaurus's live in the Jurassic?

In the world, as it looks like at that time. Yeah, at that time. So we've really got two continents. We've got a northern continent who's called La Raysia and a southern continent that's called Gondwana. Is it just after Panche is split up at the end of the Triassic? That's right. And so we've got a big seaway between the two,

but the Atlantic's only just beginning to open. So there is some separation between North America and Europe, but they're not fully separated. There's probably still kind of routes across and through Greenland and the top up there. And so we have Stegosaurs living in North America, in what is now the Western US, most famously, of course, things like Stegosaurus. But then we have Stegosaurs all across Europe. We have tons of stagosaurs in China, we've got them in Africa and South America as well.

So, in fact, the only continents where we don't have Stegasors at the moment are Australia and Antarctica. And I reckon they were probably there. It's just that we haven't got a really good sample of the fossil record from those continents. Do we have many fossil sites for Stegasaur surviving? of all the dinosaur species, are we quite blessed when it comes to stegosaurs? Yeah, no, not really, actually. Despite the fact they're very iconic and very well known.

They're actually really quite rare as fossils. Now, Stegosaurus in North America is relatively well known, although we don't have very many complete animals, in fact, almost no complete skeletons at all, we do find lots of evidence that they were living there. They're much rarer at other times and in other places, so much less common. I mean, we only have a couple from Europe, for example,

And they're quite common in China, but China's a massive place with a long rock record. So, yeah. And also, last question before we delve into, I guess, head to tail of a stegosaurus. We mentioned already how, like, T-Rex is not living alongside stegosaurus. But in this period, like the late Jurassic, let's say, what are the key dinosaurs that would have been living alongside a stegosaurus? The other dinosaurs that we see are long, neck, long-tailed dinosaurs primarily. So these are things like diplodocus and brontosaurus and brachiosaurus and sort of one.

Yeah, the giants that you're very familiar with from, you know, when you're a kid, basically. And these, again, are all living in the Western US alongside Stegosaurus. In fact, I think currently there's about 26 different types, different species of these sauropod, long-nate-long-nale dinosaurs living alongside Stegasaurus. So they were the real kind of dominant herbivores in these ecosystems. Stegosaurs seem to be, you know, slightly more rare, not quite as common. And then we have predators, things like Allosaurus in North America. Very well known from that time period. And it's really interesting because then we go into the, into the Cretaceous period, and these

ecosystems completely change. And we don't have Stegasaur and sauropod-dominated ecosystems anymore. You know, that herbivorous kind of niche changes, and we get ankylosaurs and Iguanodontian dinosaurs occupying that instead. And also that shift from Jurassic to Cretaceous. It's not like a big world-ending cataclysm event that marks that shift, is it? Well, no, there's a faunal turnover. So the animals that characterize the ecosystems change. And this is what early geologists and paleontologists recognize, this is why they drew that line because they recognized that both in the sea, in the marine realm and on land, we actually see a kind of turnover of animals. But what caused that turnover is a little bit unclear. And some people have suggested there might have been some

sort of extinction event, but it's not really clear what might have caused it and whether this was true everywhere. And stegosaurs are one of those creatures that do die out with the turning of that, with that ecological change or gradually declined. Well, it's a bit weird because in North America, we don't see any evidence of stagosols after the Jurassic. And we do have good terrestrial ecosystems from the Cretaceous. We have good Cretaceous rocks, good fossil record. So if they were there, you know, we would have found them, I think. In the rest, in Europe and Asia, we actually do see the stagosols continuing into the Cretaceous, although they're much more minor. They're quite rare part of

ecosystems. Are these lush tropical habitats that they're living in? Do we know much about the ecosystems of the Jurassic that they existed in? Yeah, in North America, we're looking at probably seasonally arid environment, a bit variable because actually they, you know, the whole of the North American continent's big area, the area

where they were living actually is, you know, covers 12 degrees of latitude and in the north it was probably a bit wetter and then in the south it might have been quite arid. But yeah, probably seasonally, seasonally wet and probably similar elsewhere in in Europe at this time we actually have mostly marine rocks. So the Stegosaurs that we're

finding are actually, we're probably kind of floating and bloating. So their animals are being washed out into the sea, and their carcasses are floating out, and then they're eventually falling to the sea floor. So we don't really know the environments on land very clearly at that time in the UK, for example. So some Stegosaurs have been found at the bottom of Jurassic Seaways, I guess then, wow. There's a super cool specimen in the Natural History Museum. It's one of my favourite specimens. I always show it to visitors to the collection. It's not on display, but it's a couple of stegasaur tail spikes I'm sure we'll come to them.

And it's actually got bivalves so, you know, two shellfish actually encrusted on it. So like today when you have whale falls and animals kind of, you know, it forms a little ecosystem. The whale skeleton forms a little ecosystem with things living off the bones.

It looks like the same was happening with this stegasor skeleton way back in the late Jurassic. So no wild theory is that this particular type of stegasaur became a marine animal could swim. I don't think it was swimming. But to be fair, all we know of it is it's two tail spikes. There's nothing else.

So, you know, I can't rule it out. Who knows? But it sounds like the general characteristics of a stegasaur, you can identify it, whether it's in North America or the fossils are in China today. But because the ecosystem, you know, differ in those areas, you can notice, you know, how the species had unique little characteristics that differed them between other ones depending on where they live. Exactly.

And so if we focus on, like, I guess the overarching. features of a Stegasaur, and then we can delve into kind of like little details and how they change. If we go from head to tail, let's start with the head. What should we be thinking of with the iconic Stegasaur head? Well, they're very small. And actually, Stegasaur's are kind of famous. I think it's true that they have the smallest brain volume per body mass, unit of body mass of any terrestrial animal that's ever lived. Wow. So their brains are about the size of a walnut. They're very small and they, you know, these are animals that are four, five, six metres long, something like that. So yeah, they have very small heads and they have tiny teeth actually only about half a

centimetre. The crowns of the teeth are only about half a centimetre tool. So, I mean, I always thought this was probably suggested they were kind of slurping some soft material, soft pond weed or something like that. But actually, some of my colleagues have done some kind of bite force modeling and some engineering, using some engineering techniques to look at the strength of the skull. And we think actually they were, you know, they could probably bite through twigs. They probably had the same bite force as a sheep. But maybe they had this sort of gratinous sheath kind of beak covering, which is actually quite common in these herbivorous dinosaurs. So it's almost a bit like a turtle's beak and that they were using this to sort of crop vegetation. So quite a strong being with those small teeth.

And do we have lots of stegosaurus teeth surviving or stegasol teeth? No, not really. And we've not got very many stegasol skulls actually. And not very many isolated teeth either. So we have a few skulls from North America and a few from China, which preserve teeth in the jaws. So we can see where they fit and what they were like. Such a fascinating part of Stegasaw's story, isn't it, the fact that this massive, bulky herbivore, like a bulldozer today, and yet in comparison to the rest of its body, like, its brain size is the size of a pea. Well, maybe a walnut. Let's not be unfair to it. Sorry, okay, maybe I'm being into, yes, you can tell me off if I'm being a bit too street, but that's amazing. Yeah, I mean, I guess, you know, they did what they needed to do,

which was to eat and mate, basically, and, you know, that's what stuff needed to do. Make sure you don't get eaten. So, yeah, I was obviously smart enough to live for millions of years and be successful in the ecosystems. I'm guessing we don't know much about like the eyes or the nose or anything like that. No, it's quite difficult. Although we have halves of the inside of the brain case, so reptiles, the brain is encased in a kind of bony casing called the brain case. So we can CT scan, a skull, and we can look at that space that's inside, which would have been occupied by the brain. And in meat-eating dinosaurs, people have done this, and you can see kind of big olfactory lobes, which relate to your sense of smell. So a big olfactory lobe might indicate

very good sense of smell or optic lobes, which might indicate a very good eyesight. But in the herbivorous dinosaurs, the Ornithisian dinosaurs, we think that the brain probably didn't leave that quite as good impressions on the on the inside of the bones so it's a little bit more hard to see those features in these sorts of dinosaurs there's certainly nothing particularly remarkable when we look at that brain case those endocarses they're called there's nothing that you go wow you know that was an amazing had amazing eyesight or or anything like that it just kind of looks kind of average to be honest so yeah we don't we don't have a good idea about it senses really I mean, pretty much, I've told you about bite forces, I guess we know that it wasn't processing

food. Stacosaurus didn't process food in their mouths. So we chew and we break down our food in our mouth and then we swallow. Lots of reptiles don't do that. They just swallow the food down and then that digestive processing takes place in the stomach. And birds, for example, will do this and then they eat stones which help grind up food in their stomachs. Lots of the herbivorous dinosaurs actually evolved chewing like us. convergently to us, of course, you know, separately from us. But the steak of source didn't.

There's no evidence that they were, you know, doing lots of kind of food processing in their mouths or anything like that. Well, let's go towards the body then. So should we be imagining a long neck or quite, quite a thick neck, I guess? Well, actually, different stegosaurs, there might be different answers for that. Great. We have Stegosaurus, which we know very well, which has a kind of totally average-sized neck,

I'd say. You know, I mean, it's got to be able to reach the ground, otherwise it couldn't drink and eat. But, yeah, it's not particularly long. It's not particularly notable. And then we have a dinosaur from Portugal, stegasor called Miragaya. And that actually has more neck vertebrae than most long-necked, long-tailed dinosaurs. It has 17 neck vertebrae, which is loads. relative to most stagosaurus, which have between 11 and 13.

So that one looks like it had a bit of a longer neck. So when we described that, we actually described that back in 2009 and named it, and we suggested that it was kind of mimicking a sauropod, a long-tailed dinosaur. Do you think the primary purpose of that would be to reach higher up foliage, that idea? Possibly, it's a bit difficult to tell. There's this idea that stegasors might have been able to rear up onto their hind limbs and use their tail as a kind of bit like a tripod. It's called the tripodal stance.

and maybe this helped them reach higher into trees. So it's possible that they were doing something like that. And there's a little bit of evidence in terms of where their centre of mass is that suggests they might be able to do that. So your centre of mass is like, you know, it's like the balance point of your body. So you can imagine it's like the balance point of a seesaw. And in Stegasaws, that seems to be over the hips, which means it would be quite easy for them to kind of push off and adopt that kind of position.

It's a bit circumstantial. We don't really know whether they did it or not, of course. But yeah, they might have used it to reach higher into the trees. We're talking about the legs. So my classic image of a stegosaurus from cuddly toys to shows up walking with dinosaurs and the like is a big body and then stumpy legs. Is that the idea we have? Yeah, well, all of these four-legged herbivorous dinosaurs, in fact, all the four-legged dinosaurs evolved from two-legged ancestors. So unlike with mammals where often we see kind of, well, you know, we as mammals evolved from four-legged ancestors.

the mammals often have quite even length hind and forelimbs. Because the two-legged dinosaurs that were the ancestors of the four-legged ones had shorter four-limbs than hind limbs, what we see in a lot of the herbivorous dinosaurs, the bird-hipped dinosaurs, things like stegosaurus and triceratops and that, they actually have much shorter four-limbs than they do hind limbs. So I think, you know, sometimes we put a very mammalian kind of view on what looks normal. And I suspect actually some of these dinosaurs would look quite weird to us, you know, very, very short four-limbs. limbs quite crouched posture, so they couldn't straighten their forelimbs and they couldn't have, I can't do this without miming. It's absolutely impossible to talk about dinosaur locomotion

without miming, but they couldn't move their forelims forward and raise their arms in the air, if you like. They're almost this idea that a stegosaurus in its natural pose potentially could be kind of leaning over a little bit because the front legs are a bit shorter than the hinders. Yeah, absolutely. So its back would have been angled downwards. Oh, interesting. So interesting. If we move up the body, we've got to talk about one of the two most iconic parts of stegasors, which are these plates. First off, I mean, what is the usual number of plates that we see on a stegasor? Well, do you know, this is an interesting question, because stegasors are so rare as fossils,

particularly complete individuals, that actually we didn't know the answer to that question until we got Sophie the Stegosaurus at the Natural History Museum, the Natural History Museum's one, because we had no stegasor that preserved all the plates in the right place down the spine. But now we, well, Sophie at least, has 19 plates and spikes down its back. So obviously we don't know whether that's typical for other stegasors. And there's a difference with stegosaurus. Stegosaurus and some of its very close relatives seem to have plates that are offset. So they're not paired down the back.

They're two rows of plates, but they're offset from one another. Whereas most other stegasors appear to have paired plates because we've actually got, although we haven't got the whole array, we've actually got plates from the left and right that are identical to each other. So it's not just one line of plates along. which is also a classic image you get, there are multiple lines of plates. Well, there's two lines, yeah.

Oh, sorry, there's two. Two rows of plates, yeah. Right, that's so interesting. And so what are they made out of? They are bone, which is why they preserve, why they fossilise. If they were soft tissue, they wouldn't fossilise. So they have a bony core.

However, when you look at them, they've got blood vessel channels running all over the surface. So it looks like they had a good blood supply. And they probably had some sort of keratinous covering. So this would be a material a bit like our fingernails, you know, something like that kind of a horny covering. So they would have been bigger than are preserved as bone.

The bone would have been kind of the core of the plate, if you like. And are they directly connected to the backbone, to the spine? No, not at all. They're just embedded in the skin. And this is similar to, actually, we see, they're called osteoderms, skin bone. So they're very, very hypertrophy. They're very elongated osteoderms. And we see these in alligators, actually, in crocodiles as well today.

So they have them embedded in their skin and their backs. And actually, all throughout the Mesozoic, throughout evolutionary history, of lots of different groups of animal, we actually see osteoderms cropping up time and again. So it's not particularly unusual or unique to have bony bits in your skin, but what's interesting about the stegasors and, of course, their close relatives, the ankylasors is that they really took this to kind of extremes and really hypertrophed them and made them extremely elaborate and elongate and large and flashy. Yeah, and absolutely extraordinary. He said one of the most iconic images we have in our

heads today, which leads to the big question, what do we think that these plates were used for? Well, this is not a trivial question, actually, and not easy to answer because, you know, actually being able to test ideas around the function of this, you know, we call it armour, is really difficult. There's been a number of different suggestions of what the function might have been. I mean, so I referred to it as armour and, you know, it could be armour. It could be for protection against predators. You know, if you've got a load of spikes and plates sticking up off your back, allosaurus isn't going to want to come down and take a big chunk out of your back? I guess the fact, isn't it, you've got the carnivals of the time. which are, you know, they can stand taller

than the Stegosaurus. Yes, they would have been taller. But of course, you know, Stegosaurs's flanks are entirely unarmoured. So it doesn't seem like great as a form of armour, I would have said. But, you know, yeah, it would have put off the big ones from coming down on your back, presumably. You've then got ideas that they could be for display.

So, you know, often when we see in today's animals features of the animals which don't seem to have any obvious function, look like they might be quite energetically expensive to produce. They often are related to some sort of display. Now, this could be to try to attract a mate, you know, to show off to try and attract a mate. It could be, you know, think about peacock's tail, for example. It could be for some sort of intraspecific combat. So if you think about the horns of an antlers of a deer even, or the horns of a big horn sheep or something like that, they are, you know, fighting each other for mates. It's usually something to do with mating, but it could also be, we know that lots of

these stegasols were living alongside each other in the same ecosystems. So it could be that, you know, you're making sure you're mating with the right people. So we, you know, it could be some sort of display function, not quite clear what that might be, but it could be a number of things. And then there's this idea of thermoregulation. So this is being able to control your body temperature. And of course, the closest living relatives today to the dinosaurs are the birds and the crocs. And if we want to understand features that aren't preserved in the fossil records, then we tend to look at the closest living relatives and say, well, what was the common ancestor of this animal doing? And metabolism is one of these, were these warm-blooded or

cold-blooded animals? And actually, this is problematic because crocs are cold-blooded, they're ectothermic. Birds are warm-blooded. So we don't know what the common ancestor of crocs and birds was doing, and we don't know what the dinosaurs were doing. We think that warm-bloodedness must have evolved somewhere on the line to birds, but where we don't know. So we generally think, based on a few different lines of evidence, particularly how fast the stagosaurs were growing, they appeared to be growing quite slowly relative to other dinosaurs, that maybe they had a relatively slow metabolism. They were more at the kind of cold-blooded end of the spectrum than the warm-blooded end, and thus the problem for them being massive multi-ton animals was actually losing heat.

So they would have generated lots of body heat from moving around and eating and digesting things and how you get rid of that heat is difficult when you're a great big animal. So people have suggested that maybe the plates were increased their surface area. You know, they would be able to flush hot blood into these plates and it would radiate heat out.

It's almost kind of like a ventilation kind of thing. Yeah, or like a radiator, yeah, absolutely. So the problem with all of these ideas though is actually how do you test them? You know, it's really, really difficult particularly given the fossil record that we have. So we might be able to test some ideas around display, for example, if we had a very large fossil record. We could say, well, do juvenile animals have really tiny plates and then they sort of grow really big and elaborate as they become adults?

Because we know that features that juveniles tend not to have, and adults tend to have, tend to be something to do with sex, tend to be something to do with mating. Likewise, do we see differences in males and females. Now, we don't have any juvenile stegasors, and we can't tell sex. We can't tell which are the males and which are the females. And we don't even have, you know, we would need an enormous sample size. We would need hundreds of individuals to be able to tell, you know, do one set have small plates and one set have big plates, for example, or different shape, plates. And we simply don't have the sample size in stagosos to tell that.

In fact, we don't really have it in any dinosaur, I would argue, to be able to tell that. So it's really difficult to test these ideas. And actually, I think it's kind of, it's a slightly made up question, really, because when we look at animal that are alive today that do have osteoderm, so things like crocs and alligators, what we know is they're use them for loads of different reasons. So alligators use them to stiffen their spine, so it helps when they're walking on land, which they don't do that much, but when they do, it helps them stiffen their spine. They use them as calcium reservoir when they're making eggshell.

And they actually do appear to use them for some parts of, you know, for thermoregulating. So they actually use them to help lose heat. So I think it's very likely that stegasors might have used them for all of these different reasons. And actually, you know, it's not really a debate about what they use them for. They probably used them for all of them. Yes, and you can't take away the idea that, you know, in a tricky situation, if had to defend itself, it was still quite a good piece of armour at the same time, wasn't it? Absolutely.

But is it very much the fact that, you know, the primary purpose of the plates of stegasors could well have differ depending on where in the world they lived and at what time in the Jurassic they lived? Yeah, absolutely. And we do see really different armour and different types of stegasaur. So Stegosaurus from North America had very big, wide flat plates. And as I said, they were offset from each other, whereas most other stegasors actually had much smaller armor and they were much more spine-like. So maybe not quite as good as heat radiators. Probably still would have had some, well, they definitely would have still had some function in, you know, thermoregulation.

But maybe not as great. But they might have been better as actual, you know, protection. If you've got a big spike sticking out your back rather than a very thin plate, it might be more useful, you know. I sometimes say that I think that alasaurus could have chomped through stegosaurus's plates like us eating Doritos. But, you know, I don't know, I don't know whether that's true or not, but, you know, yeah. But do some stegosaurus, we're going to get to the spiky tail very soon, I promise, building up to it. But do some stegasaur types, do they have spikes on their body as well instead of plates? Yeah, so some actually quite a lot, we think, had shoulder spikes.

So spikes, they again, embedded in the skin, but over the shoulder blades and then sticking out backwards. So there's one in China called Gigant Spinosaurus. And as you might guess, it has a gigantic spine. It's about a meter and a half long that sticks out from its shoulder region. And that one was actually, we know that they were shoulder spikes because that one, they were actually found in place alongside the arms. And lots of Stegosaurus seem to have this. Stegosaurus doesn't.

I think we've got so many, or we've got several pretty good specimens of Stegosaurus, if they had them, I think we would have found them by now. There are some individuals of Stegosaurus that seem to have kind of throat armor, these kind of, it's almost like chain mail, these little tiny ossicles, like little tiny like beads almost of bone in the throat region. And we haven't found them in any other stegasaur, but we haven't got such a good fossil record of other stegasors, so it's possible that some of them did. To protect that vulnerable area, maybe? Well, yeah, it's a vulnerable area, isn't it? Wow. And so, and the skin on the body of a stegasaur, generally that's less armored than the

plates and the spikes? Yeah, just scaly skin. Just scaly skin. There we go. Well, then let's go on to the last part of the stegasaur, which is, of course, the tail region. And what is this other iconic part of a stegasaur that you have with the tail? So stegasors have spikes at the end of their tail. Stegosaurus has four. Some people refer to these as thagamizers. That's the word I've seen. Okay. Well, so this word comes from a far side cartoon. And it is a caveman who is being, he's called thag. And he meets his demise thanks to a stegasor tail spike. So it becomes a thagamiser. And this, I have actually seen it being used in one scientific paper. I'm kind of against it, like it's used in the sort of dino nerd world. I'm against it on the basis

that we have enough terminology in science. Like we don't need any. I mean, they're just spikes. Let's just call them what they are, guys. Spikes. We don't need this. Yeah. We don't need it. And then people try and say, oh, no, isn't the thagomizer the whole? No, no, no. It's not. It's literally a made up word that was made up in a comic. It's nothing. It's not a thing. But anyway, yeah, so there are spikes at the end of the tail. And actually, people have have done some modelling to look at if the Stegasaur switched its tail from side to side, what would be the forces that would be generated at the end of the spikes? And we know that they would be pretty bone crushing. So, you know, it could do Allosaurus's legs some damage,

I think, if it was swinging its tail from side to side. So, yeah, probably a weapon. And the Stegosaurus has four of them. Yeah. But does the number of spikes on the tail differ between the other stegasors? It seems to. We don't know. We haven't got complete articulated skeletons of other stegasors. But many of them seem to be much more spiky, as I said.

And there's one called Kentrosaurus, for example, which is well known from Tanzania. And that seems to have spikes all the way up its tail. Yes, Kentrosaurus is another interesting example. I had in my notes down here that wanted to mention it as well. because, and that is another type of stegosaur, is it? It just looks a bit different than your classic stegosaurus image. Yeah, it's a different, it's a different species, yeah. I mean, it lived in, it lived in Tanzania, so in Africa, but at the same time as stegosaurus, roughly.

And is this idea, like, the swinging of the tail, should we be imagining almost like, kind of the big hip motions of today to generate that power, or is it more that the tail had more flexibility almost to kind of go almost to a right angle or then be switched that way, or is it the whole body bringing that kind of weight? in an attack, do we think? The tail could flex, side to side, not up and down so much, but side to side. So I think it would have swung its tail. But also, remember, again, we do tend to have a very mammalian-focused view of what things look like.

And the tail of a dinosaur would have been much more like that of a crock. So they have these incredibly long muscles that run all the way along the tail, very, very chunky, very robust, so very muscular. and those probably would have been used to swing the tail. I've got to ask because, I mean, if you haven't, I'd want to be there if you'd do it at any time. But have you guys at the NHM or have paleontologists try to recreate a tail to swing, you know, kind of get this idea of the body mass and then recreate some spikes and then have a dummy or something there, maybe like a piece of pork or whatever, a piece of meat,

and to kind of test just how brutal a swing could have been. So we have not done that. Although my colleague, Hyrit Malison, who was at then, Museum Fanaticanda in Berlin where Kentrosaurus is, most of the fossils of Kentrosaurus are housed and is on display there. He has done it digitally. So he's done it computationally

and calculated those forces at the end of the tail spike. And that's why we know that they could have kind of impacted bone is because he's actually calculated the forces. So yeah, analog models are more difficult to come by but doing it digitally is a little easier. Come on Susie, we've got to make it happen. It's going to be hilarious.

I love to see it. But that is kind of the classic anatomy of a stegosaurus, isn't it, of a stegasaur? Is there anything we've missed that we should also mention about how its body functioned? Oh, well, you know, there's so much we don't know, really. So I don't think so, but, you know, there's loads we don't know about the paleobiology of stegasors because we just don't have that good of fossil record. Well, it was also interesting what you mentioned there, that we don't have any juvenile stegasors surviving. So do we not know much about young stegasors or how they raise their young and kind of when the plates developed and stuff like that?

Yeah, no, we know virtually nothing. I actually should say there is one juvenile that I'm aware of, at least, that was from Dinosaur National Monument in the Utah, in the US, and it's very incomplete, so it's just some hind limbs and some forelimbs and a little bit of pelvis. I don't think there's any plate. There might be one tiny plate, but it's very, very fragmentary, and that is the only baby stegasaur that we have, and as I say, very, very fragmentary remains,

so very difficult to say anything about it. We don't have any nests of stegasaur. we'd have any eggs. Actually, I think probably we think now that for these sorts of dinosaurs, the bird-tip dinosaurs, that primitively, and stagosaurs are fairly early

members of this group, that they probably had soft-shelled eggs. So they weren't laying eggshells, they weren't laying eggs with calcite egg shells and it's the calcite that preserves in the fossil record. So when we found dinosaur eggs, they tend to be, you know, their calcite ones. Yeah, and there has been

some pretty recent discoveries of more of softer, kind of more leathery shelled eggs from some of these herbivorous dinosaurs. So I think that's probably a good explanation for why we don't have more nests or evidence of them. But, you know, even so, we might expect to have more young ones, but we don't. So we don't really know whether they were living in family groups. We don't know whether they were herding. We don't know whether they had kind of, you know, they sometimes call them nursery herds. You know, this idea that maybe all the babies were living together and maybe a separate environment from the adults. We we really don't have any clue about any of that.

When you read my next question, which was going to be like, like you imagine the big herds of iguana don, or even the sauropod herds, isn't it? It seems like Stegosaurus, the question is still out there. But I guess also with their armour, I mean, do you see with like ankylosols later in the like that they are more individualistic, I guess, or more on their own? Again, I don't think that we have a great answer to that.

And I don't think that all of them, they might have been doing different things. So we have loads of different, I mean, ankylosals, there must be 60 or 70 of different types of ankylosaur. And it's possible that, you know, different ones were doing different things. I think it seems quite likely that these dinosaurs were living in herds or, you know, groups of some form just because it's a really sensible way to defend yourself from predators. And I think we're very clear that these animals were not running very far. You know, these are not fast-moving animals.

They're not running away from predators. These big, big predators would have been slow moving and the herbivores would have been probably slower moving. So I think, you know, there wasn't any pursuit predation going on, so they had to come up with different ways to defend themselves. And that could be why, one of the reasons why we see these very kind of elaborate structures on all these sorts of dinosaurs. So this armour in Anpilosaurus and Stegasors, and then we have things like the horns and frills in the serotopsines and the triceratops-like dinosaurs. So, you know, it could be that they're using these kind of bizarre display or, you know, possibly defensive structures to help defend themselves from predators because they can't run away. I think, you know, herding is kind of, it makes sense. We just don't have any evidence for it.

And talking about predators quickly, we've already mentioned allosaurus, but do we think that there were any other kind of big predators that would have been the main, I guess, enemies, the main threats to stegasors? Yeah, there are other big meat-eating dinosaurs around at the same time. So in North America, we've got ceratosaurus, marshesaurus, Bovosaurus, living alongside them. Yeah, I mean, that allosaurus, certainly in North America, living alongside Stegosaurus,

alasaurus is by far the most abundant predator, you know, by miles. The other meat-eating dinosaurs are much, much rarer. So really, you know, the Morrison formation where these dinosaurs are found, where Stegosaurus and Alisaurus found. Allosaurus rule de Morrison. It was doing all the eating of everything, I think.

Well, I have in my nose one particular type of stegasaur that I know is close to your heart, that it doesn't work around, but please forgive me if I mispronounce the word of it. Adratiklitt Bulaffa. Pretty good. I mean, I don't really. We named it in Amazir, which is the language of the Berbers in the Middle Atlas Mountains in Morocco. And so I'm not going to pretend that I speak Amazir either. So you can go nuts and pronounce it however you want.

It doesn't mind. I'm not going to try again. Okay. I'll say once again, I'll say once again, Adratiklut Bulafer. So can you tell us about this particular Stegasaur? This is the name I've never heard before. Yeah, so this is a stegasol that we named back in 2020, and it's from the Middle Atlas Mountains of Morocco. It was the first Stegasaur found in North Africa. And it's from the Middle Jurassic. So it's really early on in the evolution of the Stegasaur. So when we first came across these fossils, which were actually for sale, they were for sale in a commercial fossil dealers in Cambridge, actually, and we spotted them and my colleague at the Natural History Museum is before I worked there, but he decided to

acquire them for the museum, rescue them, if you like, from the commercial, market and bring them into public ownership. And so we worked on these specimens. When you buy specimens on the commercial market like this, you often lose the contextual data that comes with them. So it said that they were from the middle Jurassic of the Middle Atlas Mountains of this town called Ballmain. But of course, we didn't know whether those rocks were accurately dated. We didn't know whether that was, all that information was correct. So I decided to go and try find out where this specimen was from. And I went with a colleague who's a shark guy. He collects sharks teeth. Oh, we love, we love fossil shark guys as well. Don't your eye. Don't you. That's good

to hear. That's good. So he had been to Morocco a bunch of times because there's loads of sharks. You can collect sharks teeth in Morocco. And anyway, he knew all of the commercial dealers. And so he and I basically worked our way back down the commercial supply chain to the guy who dug the specimen out of the ground. It was amazing. It was a farmer who lived on the side of a hill. I showed him the picture of the specimen and he was able to just kind of take me to the hole and was like, this is where I got it from. And I worked with a geologist from the local university who is an expert in the rocks of the area. And so he was able to come with us and then say, yeah, this is all Middle Jurassic. This is this formation. You know, these are these rocks. Because

he'd been working on these rocks for his entire career. And that was fantastic because we were able to demonstrate, you know, exactly where the specimen was from, that it was indeed middle Jurassic, making it one of the oldest stegasors we know in the world. And it's actually gone on to result in a really long-term collaboration between myself and the geologist and his group now. We've set up Morocco's first vertebrate paleontology labs at his university and doing lots and lots of work with them and training students there to be vertebrate panellologists. So it's been an incredible project that started with a few stagocor bones for sale in

a fossil shop in Cambridge. That's great. And to discover the first known stegasors in North Africa today in the Atlas Mountains in Morocco. Yeah, that's right. Yeah. And it's a very fragmentary specimen. I mean, we just have the fall in part of the for limb and some vertebrae. And that's it. So, you know, we hope that we're going to find more there. Do you think it's almost certain then that there are still so many different species of different types of stegasors from the Jurassic and maybe into the early Cretaceous that we just don't know about yet? Yeah, definitely. Africa is virtually unsampled, you know, relative to North America and Europe. We just haven't been looking there very long. And there's lots of, you know, geopolitical and sociopolitical reasons why it's sometimes difficult. So they have Middle Jurassic Rocks. It's time period that I'm really interested in because it's when we really see, you know, all of these different groups of dinosaurs get going and really radiate and diversify and sort of take over. Middle Jurassic Rocks are present in places like Niger as well as Morocco. But it's difficult. It's dangerous. The risk assessment that I would have to write would be so long to be able to be able to work in some places that, you know, we can't go there. Many places, as I say, you know, Morocco had no vertebrate paleontologists working in the country in university.

So we set that up. So there are lots of reasons why these places aren't sampled. And the African continent today, if going back into the Jurassic mindset, are we thinking the north of the emerging Atlantic Ocean or the south? Where should we be thinking? Yeah, south. So southern hemisphere. And that's the area where there haven't been stegosaurus or known of until now. Well, Kentrosaurus, which we mentioned earlier, that's from Tanzania.

So that's been long known about. That was first discovered by the Germans in the 19, early part of the 20th century. And there's also a little bit of material from Argentina. And it's quite cryptic in Argentina because the specimen was originally described, not as a stegasaur, but as a kind of general early ornithician, bird-hip dinosaur. The bird-hip dinosaurs are part of the group that stegasors belong to. And actually myself and two other colleagues got the paper to review. So, you know, when we publish a scientific paper, the first part of the process is you submit

it to a journal and the German goes, well, this looks interesting, but we're going to send it to some other experts to see what they think. And this is the process of peer review. We all do this to each other's papers. We all read each other's papers and comment on them. And it's part of, you know, our job as scientists to review what other people have written and make comments on it. And I got this paper and I went, well, that's a stegasor.

And so did my two other colleagues. and we all sent our papers back independently of each other, of course, not knowing this, saying, well, we think these arestegosaurs. And the authors came back and said, you know, we think it's a stegasore too, but we keep, we keep doing these quantitative analyses that look at the evolutionary relationships of these different animals. And we can't make it be a stegasaur. It just doesn't want to be a stegasor in our analyses. But anyway, you know, subsequently we've shown that this animal is almost certainly a stegasor. It looks exactly like a stegas, it's definitely stegas. It's definitely stegasol.

But it's very, very early. It's the world's oldest. So it's quite primitive. And that means it has a number of features that, you know, kind of bridge the gap between some of these earlier dinosaurs and some latest snakes. Well, it's really exciting having you on because, you know, you're someone at the forefront of the developing story of Stegosaurs and how, you know, now in the 21st century, many of us growing up would have heard of Stegosaurus since, you know, since we were kids and TV programs, but to think that actually more is being known about them, you know, all the time, thanks to people like yourself and other papers writing about them and new discoveries being made.

So it's really exciting field for the future. I must ask, although, the evolution question, is it a fair question to ask what we think Stegosaurs evolve into in the Cretaceous? Or do we think it just kind of dies out and then there's just a new type of armoured dinosaur that comes to the fore? Yeah, they went extinct. So they don't evolve into anything. Our evolutionary trees, we make evolutionary trees.

We reconstruct evolutionary relationships in kind of a semi-quantitative way, I will say. And, yeah, the evidence from that is that, yeah, they just go extinct. Susie, this has been such a fun chat. Growing up, I've already mentioned the series, the original series Walking with Dinosaurs as being a big influence. And I think it's been a big influence on so many of us,

like at the end of the 1990s, beginning of the 2000s. And Stegosaurus's depiction there. I mean, what do you think of the depictions of Stegosaurus in the media world and their attempts to give us an idea of what Stegasaurus looks like?

I think generally they're very good. You would have to show me what stagosaurus looked like in the original walking with dinosaurs. I can't remember what they did with it. Quite like the classic with the big plates and the very small head. I think it's a fight against an allosaurus in a narrow kind of ravine. I think, you know, all of this is entirely plausible.

I think the things that I see sometimes where I go, oh, that's a bit wrong, is when they make them run. So it's actually less common with stegosaurus than you sometimes see with something like triceratops where you saw them, you see them kind of galloping. And there was the recent walking with dinosaurs. they had triceratopsies running around and I was like, no, no, no, no, no.

They weren't doing any of that. There was no, there was no galloping around. This is ludicrous. But, so that is one thing that gets my goat. But generally, I think they do pretty well with stegasors. Like, you know, the thing with stegasors is that we know so little about them that you've got a lot of latitude, you know. Which makes them really fun.

Yeah. And greatest kids' toys and, you know, from everything. And then in the media today, Suzie, this has been absolutely great. We've covered so much, but is there anything else you'd like to mention about Stegasors before we finish. Oh, my God. I think I've told you everything I know. Good. Well, I've done my job well then. It just goes to me to say, thank you so much for taking the time to come on the show. Thanks for having me.

Well, there you go. There was Dr. Susie Maideman talking all things Stegosaurus. I hope you enjoyed the episode. Thank you for listening. Please follow the ancients on Spotify or wherever you get your podcasts. That really helps us and you'll be doing us a big favor. If you'd also be kind enough to leave us a rating, well, we'd really appreciate that. And don't forget, you can also sign up to History Hit for hundreds of hours of original documentaries with a new release every week. Sign up at Historyhit.com slash subscribe. That's all from me. I'll see you in the next episode.