Chapter 1: What significant event marked the beginning of the Age of Dinosaurs?
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We are covering the whole age of dinosaurs. So over 100 million years of paleontology from Triassic to their extinction. with a fan favourite guest returning to the show, none other than Dr. Henry G. I loved doing this conversation. You're going to hear what my favourite dinosaur is, what Henry's favourite dino is, and so many other things.
I think my favourite part of this interview was addressing the question of whether dinosaurs did swim. or not. Still one, but there's a big bone of contention around it. But we cover that and so much more. Henry, as always, he's funny, but he's also incredibly engaging at the same time. I really do hope you enjoy. Let's go.
250 million years ago, our world witnessed the greatest mass extinction event in its 4.5 billion year history. 90% of life was wiped out. It's known as the Great Dying for a reason. The world took millions of years to recover, but ultimately, it did. This Great Dying beckoned in a brand new prehistoric world.
At this time, Earth still only had one giant continent, known as Pangea, and it soon became full of new and diverse life. There were giant crocodile-like apex predators, herds of bizarre heavy herbivores, small creatures that burrowed into the soil, the earliest mammals. And amongst all of this emerged a group of reptiles that would go on to dominate the world. The dinosaurs.
For over 100 million years, dinosaurs would rule the lands, diversifying into all shapes and sizes. From great carnivores, to armour-plated plant eaters, to small feather-covered raptors. Until they too ultimately fell foul to their own mass extinction. Today we're going to talk you through their story from beginning to end. More than 100 million years of dinosaur history.
This is the Age of Dinosaurs with our fan-favourite returning guest, Dr. Henry Gee. Henry, legend of paleontology, it is wonderful to have you back on the podcast. Thank you very much, Tristan. Legend, I'm more of a myth. You're more of a myth, okay. Well, today we've got a big topic, Henry, but we always have big topics with you.
We've done the origins of life on Earth and we've done the rise of humans. Now we're going to cover the age of the dinosaurs from beginning to end. In about 60 minutes or so, it's another big task. Are you ready to give it a go? I'm ready. Fantastic. So with the age of the dinosaurs, Henry, where should we begin? I mean, when are we talking?
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Chapter 2: How did the Great Dying influence the emergence of dinosaurs?
But the climate was very, very extreme there. Because water could flow to the North Pole and the South Pole, there wasn't the extreme contrasts of weather that we see, of climate that we see today. There was no ice. There was no permanent ice caps. However, the Tethys Ocean, because of the surrounding continent, had very extreme climates. It was a kind of mega-monsoonal climate.
And also because Pangaea was so huge and quite a lot of it was far from the sea, there were some very, very hot deserts in Pangaea. So not the climate, but the general, well, yes, the climate of Pangaea generally was very different from the very zonal climate we have today. But there were still great extremes of temperature and weather and precipitations.
And do we get different kind of ecosystems in this great landmass, depending on the climate and the location? So do we get particular animals rising to the fore in certain places before the dinosaurs become the top predators and the top species, I guess?
Yes, things like Lystrosaurus and other reptiles live more or less everywhere, but certainly towards the poles, these were the lands where giant relic amphibians lived. Huge predatory salamanders were in the water courses. In the tropics, various things live, but things don't fossilize well in the tropics. But certainly in the deserts, that's where mammals originated.
The little tiny mammals, which were tiny things the size of shrews, were basically night and evening and early morning feeders. They used to live in their burrows when the temperature was very, very hot and come out in the morning and the evening. And we know even in those early times, Some of these animals had already specialised.
Some had teeth that could crush beetles and others lived on moths, which are softer. And as we know, a moth is a male myth. But the dinosaurs originally lived at more temperate latitudes, along with various other reptiles. And that's where they were kind of confined for quite a long time. Take it away, Henry.
What do we know about these earliest dinosaurs and where they were living, and what distinguished them from those other great creatures that were front and centre at that time in the Triassic? The dinosaurs started as kind of rather graceful quadrupeds. Think of them as kind of greyhounds with small heads on long necks, possibly like borzois.
They were related to creatures such as silosaurs or athanosaurs, which are reptiles which are kind of graceful and live and run around on four legs like kind of fast dogs. But there were a lot of other creatures like that that are related more closely to modern crocodiles, which used to be very much more various in their forms than they are now.
Among this group of creatures were the Lagerpertids, which were similar, which were probably more closely related to the pterosaurs, although the actual... transitional form of pterosaurs is unknown and they appear in the Triassic with wings more or less fully formed. So the ancestry of pterosaurs is a big question mark.
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Chapter 3: What were the key characteristics of the Triassic period dinosaurs?
Is that 220 million years ago? About 200. 200 million years ago. It was a long, interesting period. And I have to say, we are talking about the dinosaurs, but I want to... bang the drum for the Triassic because we tend to think of the Triassic as the period in which dinosaurs appeared and forget all the other amazing things that happened in the Triassic.
And we forget to realize that the dinosaurs for a long time, at least the first half of the Triassic, were very, very minor features of the fauna and tended only to live in particular places. They didn't live all over the world, which they were to do later. But the end of the Triassic was marked by one of these gigantic mass extinctions. It was one of the big five.
I mean, the end Permian that began the Triassic was the biggest. But the end Triassic was definitely there in the top ten and actually in the top five of our extinction hit parade. And that was another volcanic event. It was a bit slower to take place. to happen. What happened was Pangaea was beginning to unzip. There was a fault line in Pangaea.
As you remember in Continental Drift, North America was basically glommed up against North Africa and Europe up to as far as Norway and Greenland. And that was a very, very old seam that had been an ancient mountain range, which before had been an ancient ocean. but those old mountain ranges form the Scottish Northwest Highlands and the Appalachians, very old mountains.
But along that scene, there was a rifting, a bit like the current Rift Valley in Africa. What happened was the continents were beginning to pull apart and sediment slumped into the middle and formed lakes that came and went until eventually the ocean came in. That was the That seaway was what eventually became the Atlantic Ocean. And that caused Pangaea to start to split up.
And it was a lot of volcanism at the time. And climate changed radically. And the end of the Triassic saw the extinction of all these amazing reptiles that evolved in the Triassic, all these weird things that only ever lived in the Triassic. And only a few things came through. It spelled almost the end of the giant amphibians, although some of them did hang on to the Cretaceous.
The ichthyosaurs hung on and the ancestors of what became those other great marine staples of the dinosaur age, the pletosaurs, they hung on. And so do the pterosaurs and the mammals. And of course, the dinosaurs, they managed to hang on and replace everything they hadn't originally replaced on land.
So they became the dominant group of creatures on land at the end of the Triassic, after that war. great rifting. And I remember a cartoon I saw in Punch once of a large, rather dim-looking dinosaur standing over a widening crack in the earth. And a small, intelligent-looking dinosaur says, I'd make your mind up soon if I were you. The continents are beginning to drift apart.
So it was in that landscape that the early Jurassic period, which followed the Jurassic, that the dinosaurs really came into their own. I mean, Henry, it's fascinating because we always associate the dinosaurs with, you know, they're ultimately going extinct with the other extinction events that we'll get to later. Yes, spoilers, spoiler alert. I'm sorry to jump ahead.
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Chapter 4: How did dinosaurs evolve during the Jurassic period?
I've always got time for iguanodon and its thumb spikes, which I remember you saying in a previous conversation, you know, would have been great for hailing cabbies. But since cabbies hadn't been existed for millions of years, they weren't great for much else. But evidently they were successful.
We could go down so many different avenues from all you highlighted there, painting a picture of this ever-changing Jurassic world. I will ask about those biggest dinosaurs, though, because you mentioned how they're on four legs again. They're quadrupeds.
Does this almost seem like, I don't think it's going backwards in evolution as such, but you mentioned the importance of bipedalism earlier for dinosaurs. And yet, when you see some of these dinosaurs get very big, it's like they abandon the bipedalist aspects and go back to going on all fours because they are that much heavier. Yeah.
I think what happens if you are an eater of vegetation and become quite large is that you have to eat an awful lot of vegetation to survive. And vegetation takes a lot of digestion to release nutrients. So what happens when you see herbivores generally, they usually have large guts in which the vegetable matter ferments. We see this today.
Cows have this four-chambered stomach in which the bits of the vegetation come up and are regurgitated and get ground up. And they're big. And all the herbivores we see are big. If they're small, like rabbits, they have some other kind of fermentation or they eat their own half-digested poo and digest it again. So it's the digestion. And the herbivorous dinosaurs solved this by becoming...
I mean, amazingly big. And the question has often been, how is it that these dinosaurs became so big when mammalian herbivores never got larger than maybe four meters, five meters at the shoulder? Yeah. And also these ancient rhinos, which hornless rhinos, they were even bigger. But they were absolutely nothing to Argentinosaurus.
And some of these things were maybe weighed 50 to 70 tons and were 100 feet long. I mean, just gigantic. But the key is that dinosaurs were built in a completely different way. And the key to that was the way they breathed. Now, when you and I breathe in, you know, breathe in, breathe out, breathe in, breathe out. Failure to master this and reaching nirvana will be the least of your problems.
But the thing is, it's not a very efficient way of gas exchange because all the oxygen that comes in on your intake has to be replaced by the carbon dioxide coming out. And it all mixes up. So you never really get a full breath of fresh air each time you breathe. Now, but in dinosaurs and also birds, which is very, very crucial, they have a completely different way of gas exchange.
Now, OK, they breathe in and breathe out through the same hole, but the lungs are connected to lots and lots of other air sacs that permeate the rest of the body, including the bones. So the bones of dinosaurs and also birds are very hollow and they're full of these air sacs. So dinosaurs were probably, they could grow bigger because they were mostly full of air.
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Chapter 5: What types of dinosaurs dominated the Cretaceous period?
The problem with birds is they have very fragile skeletons. I mean, I mentioned the hollow bones. I mean, when they die, they just shatter. So there were a few bits and pieces that nobody could really fit into anything. And there were some upper Cretaceous
birds from kansas and nebraska which in the upper cretaceous were by the sea it was there was a huge seaway that went from north in north america from north to south at the time and there was ichthyornis that looked like a seagull with teeth and there was hesperornis which was a big diving bird which had already reduced its wings in a way like penguins or something like that
So obviously there was a lot going on that evolution hadn't preserved until the late 90s when reports came through of fantastic, beautiful deposits in China
which were of lakes that had no oxygen, so no decay bacteria, and lots of volcanoes, so everything entombed in ash layers, which preserved birds with feathers, dinosaurs with feathers, mammals with furry coats, and the remnants of their last meal. And you have to remember that mammalian paleontologists usually only look at teeth. They rarely get any more.
So what we now know is that at the end of the Jurassic, there was quite a lot of evolution of feathery forms among very small dinosaurs. Archaeopteryx was just one. There were some very, very peculiar ones called Scansoriopterygids that had feathers, but the wings were bat-like, made of membranes. There was a little dinosaur. And the Scansoriopterygids...
very long name, they could sit in the palm of your hand. They were the size of a thrush. And then there were dinosaurs called like Microraptor that was more crow-sized, that had wings on its front legs and its back legs. So it was a kind of biplane. And there were loads and loads of these.
What tended to happen, there were three groups of dinosaurs that evolved around then and into the Cretaceous, the dromaeosaurs, the troodonts, and the birds. Now, dromaeosaurs include some of these very ferocious velociraptor-type things with a great big slashing claw on their hind legs. Troodonts were similar, but they had very large brains and binocular vision.
And people have thought that if the dinosaurs hadn't died out, spoiler at the end of the potatious, they might have become of humanoid intelligence. All that's pretty speculative, of course. And then the birds. But because these things at the time were all kind of similar, it's quite hard to tease out one from the other.
But certainly there was a flurry of evolutionary activity at the end of the Jurassic period going into the Cretaceous period, which produced these small feathered dinosaurs. Now, many other dinosaurs were feathered, even quite large ones. I mean, there's some very, very odd
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Chapter 6: What evidence supports the asteroid impact theory for dinosaur extinction?
The carnivores became very varied. There were big ones, little ones, and huge ones, like at the very end of the Cretaceous, our friend Tyrannosaurus rex, which lived by battling huge armoured dinosaurs, such as Triceratops and Ankylosaurus. Tyrannosaurus Rex, everyone's favorite, probably except my wife, she prefers Priceratops, but it's a good, good reason.
It was five tons of muscle and bone and teeth that had the shape and consistency of bananas if bananas were made of carbon steel. and it could crush right through bone. And we know this because we even have Tyrannosaur poo, and Tyrannosaur poo fossilizes well because it's mostly made of crushed bone.
So nobody really knows if it was a scavenger or it actually ate live prey, probably a bit of both. But nothing like it has been seen before or since. The only bigger carnivorous creatures on Earth were aquatic ones, the pliosaurs, which lived in the Cretaceous period. And they would have made Tyrannosaurus look like a big girl's blouse. I mean, they were just, you know, ferocious creatures.
Of course, by the end of the Cretaceous, the ichthyosaurs had become extinct. They were really, they became extinct in the middle of the Cretaceous. But we still had in the marine realm, gigantic sea serpents, you know, the mosasaurs that were gigantic sea lizards, closely related to Komodo dragons, only much bigger and with lippers.
And the plesiosaurs, which looked like snakes threaded through turtles. And of course, the pliosaurs, these immense, short-necked, huge-headed lizards. plesiosaurs that were the primary predators of the sea alongside turtles as big as Volkswagen Beetles and ammonites, these mollusks the size of truck tires. So there was a big stuff in the sea in the late Cretaceous as well as on the land.
And in the air, too. Now, because the climate was quite mild, there wasn't too much storm and wind, these pterosaurs could evolve huge sizes. The biggest aeroplanes just soared. They didn't need to flap. They soared. And they were some of the latest pterosaurs. They were so big they didn't fly much at all.
They just walked around on the ground with their legs and their wrists and their wings sticking up and their huge necks looking like gigantic animated marquees. And some of the very last ones could have stood eye to eye with a giraffe. Is this the one which is Quetzalcoatlus, the Aztec serpent god of the sky? Quetzalcoatlus is one, but there were even bigger ones called Azhdarchids.
I can't remember if Quetzalcoatlus is an Azhdarchid. But there was one called Aramburgiana. I think they're known from the Middle East. These very, very large ones. Nobody knows if they could fly, but if they could fly, they just needed to open those enormous wings into a slight breeze and they'd take off. but they could only live when the climate was fairly gentle.
At the end of the Cretaceous, it got more stormy and they would have just been blown out of the sky like umbrellas. And so towards the end of the Cretaceous was the most amazing world of enormous carnivores on land at sea, enormous and middle-sized herbivores on land, but also tiny ones because In the Cretaceous, the first true birds appeared.
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Chapter 7: How did the extinction of dinosaurs affect the evolution of mammals?
And there's a chap called Brian Ford who wrote a book saying too heavy to walk or something that makes this view. But I have to say, these views are now no longer valid. current. They've been, shall I say, blown out of the water by other evidence from modeling their weight distribution. Because sauropods weren't like elephants. They were like birds. They were very lightly constructed.
They couldn't walk on land. And to do with the sediment in which they were found. Also, we now know that the metabolism of dinosaurs was much greater than we thought. They weren't lumbering great reptiles. They were very alert, busy creatures. and they were quite capable of living and surviving on land.
But there is no reason why some of them might not have swum in the way that mammals that don't usually swim do swim, like elephants and other things. They could have migrated between various islands by swimming. This is not impossible. I mean, if you look at a skeleton of a golden retriever, you wouldn't know that it was a capable swimmer.
If you look at a skeleton of a goat, you wouldn't believe that they can climb trees. So it's very hard when you just look at a skeleton to dismiss the use of occasional lifestyle choices like swimming. So let's move on to the late Cretaceous. And you've already mentioned those well-known dinosaurs like the Tyrannosaurus rex, the Triceratops, Ankylosaurus with this massive club, isn't it?
And I think, how could any ferocious carnivore try and take down a massive armoured-plated dinosaur like an Ankylosaurus? It's surely just a death wish. Those animals, those dinosaurs feel impregnable. You know, if there is an animal that evolves, there's another animal that's evolved to eat it.
Tyrannosaurus was very big and not only had enormous teeth and neck muscles that could penetrate bone, it had enormous hind legs that could pin anything down, maybe turn it over and, you know, scrape it out. Usually Ankylosaurus was a kind of bowl of ramen noodles. I don't know. But it seems to have been a specialist in eating these armored dinosaurs, certainly Triceratops.
There are Triceratops fossils that seem to have a bunch of wounds from large carnivorous dinosaurs in their bony neck frills. And there are, I think, large theropod dinosaurs with wounds that might suggest they'd been in battle with an armored dinosaur or perhaps another large carnivorous dinosaur. So these things were tough and these were things were tough and ruthless.
They certainly weren't rough and toothless. So they would have been specialized for this sort of thing. It's kind of an arms race as herbivores evolved stronger defenses against carnivores and carnivores become more fierce and powerful to tackle the herbivores. And were real-life velociraptors as ferocious as they've been depicted in the media today? Probably.
There was always a kind of, in the ecosystems of the dinosaurs, for the small, fast-moving carnivorous dinosaur. I mean, back in the Triassic, there were these things called consognathus, which was small, fast-moving dinosaurs that would evet small things like insects and small mammals and frogs and things. Velociraptor was about the size of a turkey or a chicken.
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Chapter 8: What were some misconceptions about dinosaurs and their extinction?
that the layer in the rocks that separates the Cretaceous period from the overlying rocks is very thin and has a concentration of a metal called iridium that's very rare on Earth, but is actually quite common in certain asteroids. And this was found in Italy, in Denmark, in America, I think in New Zealand, so all around the world.
And a couple of physicists, Luis and Walter Alvarez, who are father and son team of physicists, they worked out the sedimentation rate of this iridium and showed it would have happened very quickly. Also around the Gulf of Mexico are what are called tsunami beds. At the end of the Cretaceous, the rocks are all kind of jumbled up, looking like there was an immense disturbance, like a tsunami.
And eventually the smoking gun was found. Underneath the Yucatan Peninsula is a circular structure that was originally discovered by Mexican oil geologists. It was part of the state oil company of Mexico. They found this circular structure about 160 kilometers wide. And that's since been buried by other sediment.
But that seems to have been the place where an asteroid 10 to 20 kilometers in diameter hits the Earth. And it would have hit the Earth. It would have given it a great old smack. and it would have gone right through the crust. And now a lot of the sediments it penetrated were full of sulfates. It was gypsum from an ancient seabed where it had all evaporated.
And that produced a lot of sulfur dioxide into the atmosphere that poisoned the seas. The smoke would have basically... hid the entire Earth from the sun for years and years, the actual blast wave of the impact would have been felt for at least 1,000 kilometres around. All the trees would have been flattened and there'd been widespread wildfires.
Well, not surprisingly, this had a big effect on all the wildlife. Now, all the dinosaurs that weren't birds disappeared. There have been claims that some survived, but none of these claims have been substantiated. All the big marine reptiles, the mosasaurs, the plesiosaurs, and so on, they died out as well. As well as the big truck-tire-sized ammonites, they died out as well.
And quite a lot of other things died out as well. Quite a lot of these groups of mammals died out, all except four of the 20 or so died out. and quite a lot of plants. So it had a big effect on the ecosystem. But of course, everyone remembers the extinction of the dinosaurs, what we now call the non-avian dinosaurs, particularly because they were the kind of poster child of the Cretaceous.
They all disappeared. Now, like all overnight sensations, this took a long time in the telling. It now appears that the origins of the asteroid that wiped out the dinosaurs was in a collision in the inner solar system between two other asteroids about 160 million years ago. in the Upper Jurassic, so everything was evolving on Earth unaware that its cards had been marked.
This collision produced a magazine of a thousand fragments which started migrating into the inner solar system, and one of these was the asteroid that wiped out the dinosaurs. How can we know this? That is insane. Well, just from very, very patient examination of rocks, we know that the, and orbital parameters of asteroids.
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