Dinosaurs didn’t die out when an asteroid hit Earth 66 million years ago. Get ready to unthink what you thought you knew and journey into the deep, dark depths of the Jurassic. The discovery of the first feathered dinosaur in China in 1996 sent shockwaves through the palaeontological world. Were the feathers part of a complex mating ritual, or a stepping stone in the evolution of flight? And just how closely related is T. rex to a chicken?
‘This is one of the best dinosaur books that has appeared in years.’ Philip Currie, Professor and Canada Research Chair, Dinosaur Palaeobiology, University of Alberta
science sport/australian history
John Pickrell
Award-winning journalist John Pickrell reveals how dinosaurs developed flight and became the birds in our backyards. He delves into the latest discoveries in China, the USA, Europe and Australia and uncovers a thriving black market in fossils, infighting between dinosaur hunters, and the controversial plan to use a chicken to bring dinosaurs back from the dead.
Flying Dinosaurs How Fearsome Reptiles Became Birds
John Pickrell
Foreword by Philip Currie
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Introduction: A whole new world The revelation that birds are dinosaurs and the discovery of many stunning fossils of feathered dinosaurs in China has opened up a window into an unknown prehistoric world. Imagine, if you will, a world filled with billions of dinosaurs. A world where they can be found in thousands of shapes, sizes, colours and classes in every habitable pocket of the planet. Imagine them from the desert dunes of the Sahara to the frozen rim of the Antarctic Circle – and from the balmy islands of the South Pacific to the high flanks of the Himalayas. The thing is, you don’t have to imagine very hard. In fact, wherever you live, you can probably step outside and look up into the trees and skies to find them. For the dinosaurs are the birds and they are all around you. Dinosaurs didn’t die out when an asteroid hit the earth 66 million years ago. Everything you were told as a child was wrong. The idea takes some getting used to. On the face of it, birds don’t seem that similar to dinosaurs – they’re small, bright, quick and covered with feathers, whereas the dinosaurs I was told about as a kid were hefty, lumbering beasts, scaly and reptilian in aspect, much more like a crocodile than a bird. But the clues were there all along if only we knew what we were looking for. Theropod dinosaurs (the bipedal, carnivorous variety) share numerous small features of their skeletons with birds – far more than either share with any other group of animals. An early clue to the link between theropods and birds came with the discovery of the first fossil of Archaeopteryx in a Bavarian quarry in 1861. It has been called the most important fossil xv
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ever found, not least because of what it tells us about dinosaurs. Labelled the ‘first bird’ – Urvogel in German – this prehistoric animal had wings and feathers, but also the long bony tail and teeth of a reptile. Its similarity to Compsognathus, a small dinosaur found in the same German limestones, was striking, and was even remarked upon at the time by evolutionary biologist Thomas Henry Huxley. It was only two years since Darwin had unveiled his theory of evolution by natural selection in On the Origin of Species, and it seems the world wasn’t yet ready for the revelation of the link between dinosaurs and birds. That connection would remain obscured until 1964, when palaeontologist John Ostrom stumbled upon the fossils of several lithe, athletic and deadly-looking dinosaurs called Deinonychus in the badlands of Montana. Ostrom resurrected the idea that Archaeopteryx was closely related to theropod dinosaurs such as Deinonychus, and so began the ‘dinosaur renaissance’ of the 1970s, which saw leading experts redefine dinosaurs as intelligent, speedy, warm-blooded creatures that were similar to birds.
An earth-shattering find The idea that birds were the direct descendants of dinosaurs still had its detractors, but much of the opposition fell away in 1996, when the fossil of a little dinosaur from China shook the very foundations of palaeontology. Sinosauropteryx was undoubtedly a dinosaur, but the fossil clearly showed that it was covered in a fuzzy down of protofeathers that later studies showed would have been ginger-coloured. This was the first of the feathered dinosaurs to be discovered, but whole flocks of feathered dinosaurs have since burst onto the scene, and we now have evidence for feathers of some kind in about 40 species. Most hail from the Early Cretaceous (100–145-million-year-old) shales of China’s north-eastern Liaoning Province, which preserve fossils in remarkable detail. xvi
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Every new fossil is a small pebble of proof in an avalanche of evidence confirming that birds are the descendants of the theropod dinosaurs and that these animals were incredibly bird-like. Ever since the 1870s, the hunt for dinosaurs has been a competitive business, filled with adventure and excitement. The days of Edward Drinker Cope and Othniel Charles Marsh, North America’s most famous fossil hunters, were the most ruthless of all, culminating in the ‘bone wars’ that destroyed them both. These days dinosaur fossils have become so valuable – not only to science but also to collectors – that an improbable but thriving trade in fake and illegal dinosaur specimens has become an increasing headache for palaeontologists. This has meant that modern dinosaur experts have to have the penetrating logic of Sherlock Holmes, the adventurous spirit of Indiana Jones and the wisdom of Solomon just to stay ahead of the game. Beyond confirming the dinosaur–bird link, the fossils have offered clues about how feathers evolved in the first place, and how they might have been used for flashy display purposes and insulation long before they ever helped any creature become airborne. What is most exciting about the latest discoveries, though, are hints at how dinosaurs did eventually take to the skies. We now know that the dinosaurs most closely related to birds were small predatory species, a number of which, such as Microraptor, Anchiornis and Xiaotingia – incredibly – had four wings and a long feathery tail. Their hind limbs and tails had flight feathers of the kind we see only on the forelimbs of modern birds, so it’s likely they used them to glide between the trees of China’s swampy Cretaceous forests. We also now know that dinosaurs were bird-like in many other aspects of their physiology and behaviour too. From nesting, brooding and sex, to metabolism, development and even the diseases that afflicted them, many of the traits found in birds today were inherited from the dinosaurs. The boundary between dinosaurs and birds has become utterly blurred. xvii
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Bizarre menagerie The Chinese forests of the Jurassic and Cretaceous would have been filled with a bizarre menagerie of bird-like dinosaurs, which later shared these same forests with birds themselves. Now we even know something about the colour of the feathers of the fourwinged species that flitted from tree to tree. While Microraptor appears to have had plumage of a deep iridescent blue–black, Anchiornis was dappled black and white with a red head crest. Other feathered dinosaurs were stranger still. Pigeon-sized Epidexipteryx, found in the Mid- to Late Jurassic (152–168 million years ago), didn’t use its feathers for flight at all; it had a downy covering of fuzz for insulation and four long, ribbon-like feathers that emerged from its tail. This discovery was one of the strongest suggestions that feathers were important as insulation and for display long before they were useful for flight. Weirder still were Epidexipteryx’s incredibly long fingers – its middle finger was half the length of its entire body. These strange features suggest that the creature scrambled around in the trees and may have used its long digit to skewer fat grubs in treeholes and crevices, just as the aye-aye of Madagascar does today. Even more surprising perhaps is that such well-known dinosaurs as Velociraptor (and its North American counterparts Deinonychus and Dromaeosaurus) may have had long feathers on their forearms – in effect small wings – to help them work as a pack and bring down larger herbivores. These proto-wings would have provided a bit of lift as the animals ran and leapt into the air, vicious sickle claws outstretched. Many of the dinosaurs closely related to birds had beaks too, such as Oviraptor and Caudipteryx, and the loss of teeth in birds is thought to have been one of many adaptations, along with bones full of air pockets, that eventually helped them reduce their bodyweight enough to allow for flight. Not all feathered dinosaurs were small animals, though, and fossils revealed in recent years xviii
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have shown that there were some truly giant bird-like species. These include the parrot-beaked, 8-metre-long Gigantoraptor, whose forearms and a tail were probably clad in large feathers, which it used for earth-shaking displays to woo mates, much as ostriches do today. For a while Gigantoraptor was the largest feathered animal known ever to have lived, but that all changed in 2012 with the discovery in China of a bus-sized early relative of Tyrannosaurus rex called Yutyrannus huali (which means ‘beautiful feathered tyrant’). This 1.5-tonne predator was covered in downy filaments of dinofuzz, perhaps giving it an incongruously fluffy covering similar to that of a chick. This was our first evidence that truly massive dinosaurs sometimes had feathers too, and even hinted that the mighty T. rex itself could have been covered in feathers.
Our changing view of dinosaurs The way our view of what constitutes a dinosaur has evolved in the last two decades can be seen by re-examining Stephen Spielberg’s 1993 film Jurassic Park (and Michael Crichton’s 1990 book from which it was adapted). The film’s quick-witted, pack-hunting velociraptors owed much to the picture John Ostrom had painted of Deinonychus. I was 14 years old when my dad took me to see the movie on the big screen at the Odeon in London’s Leicester Square. I remember the thrill – the fear, the joy, the wonder – of seeing a menagerie of dinosaurs brought back to life on the big screen. Never before had anyone done such a wonderful job of imagining and depicting what these animals might have looked like in life, how they might have moved and behaved, and even what sounds they might have made. In fact, Steven Spielberg’s team did such a brilliant job that today, more than two decades after the film was made, the reconstructions still look fantastic, even though we would imagine them somewhat differently today. But it wasn’t just the moving images that inspired and excited xix
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me – it was also Crichton’s ingenious plot: the idea was that we might be able to find dino DNA in the fossil record and use modern cloning technology to reread the blueprints and bring these longgone creatures back. He even came up with a seemingly plausible place to find this DNA – inside mosquitoes that had supped on dinosaur blood and become entombed in amber. But would it ever be possible to find enough dinosaur DNA to resurrect them from extinction? In perhaps the most audacious modern dinosaur project, one scientist is looking at reprogramming the development of a chicken to awaken dinosaur traits (such as teeth and a bony tail) lying dormant inside its genes, so that some day we might watch a baby dinosaur hatch from the egg of a chicken. Along with the new fossils, and renewed interest in dinosaurs, have come fresh interpretations of how dinosaurs lived their lives. In 1993 nobody could ever have predicted that we might know something about the sounds that dinosaurs made and the colours they were decked out in, but clever new methods have begun to probe these kinds of details too. Experts are also starting to pin down some of the reasons why birds survived the comet strike that doomed the rest of the dinosaurs to extinction 66 million years ago. We have learnt more about dinosaurs in the two decades since Jurassic Park than during the whole of history up to that point. The 1990s seemed like a golden age of dinosaur discovery, but fossil finds since then have dwarfed it. Around one new species is currently discovered every week, many in China, but others in South America, Mongolia and Africa. There’s so much new knowledge it’s hard to keep up, but one thing’s for certain – if you love dinosaurs, this a great time to be alive. If, like me, you can still imagine a prehistoric world filled with wonder and excitement, the best may yet lie ahead of us. If the last 20 years have taught us anything with regard to what we know about dinosaurs, it’s to expect the unexpected. Want to know more? Get ready to unthink what you thought you knew and come with me on a journey into the deep, dark depths of the Jurassic… xx
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Before we begin I want to start by clearing up some common misconceptions about dinosaurs. If you’re a dino buff then you’ll probably know all of this already and want to skip forward a few pages.
1 What is a dinosaur? Dinosaurs are a group of reptiles defined by many features of their skeletons – most particularly the fact they hold their limbs erect beneath them rather than out to their sides in a sprawling posture as lizards and crocodiles do. Dinosaurs are made up of two major subgroups: the saurischian or ‘lizard-hipped’ dinosaurs, which included the giant long-necked sauropods (such as Diplodocus) and all the bipedal, predatory theropods (such as Tyrannosaurus and Velociraptor); and the ornithischian or ‘bird-hipped’ dinosaurs, which included heavy-set and armoured species (such as Triceratops and Ankylosaurus) and herd-living herbivores (such as Hadrosaurus and Pachycephalosaurus). Officially dinosaurs are deemed to be all the animals that descended from the last shared ancestor of the ornithischian and saurischian groups. Confusingly, birds are theropods and are therefore part of the ‘lizard-hipped’ group. 2 Dinosaurs and people didn’t coexist Modern humans that look like you and me evolved around 200 000 years ago, while our more distant ancestors diverged from chimpanzees 6–7 million years ago. The last of the nonavian dinosaurs (that is dinosaurs that weren’t birds) disappeared in a mass extinction around 66 million years ago at the end of the Cretaceous period. At around the time the dinosaurs winked out, the lineage of mammals that eventually gave rise to humans and all other primates included a small squirrel-like animal called Purgatorius. xxi
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3 Geological history is vast The earth formed around 4.5 billion (4500 million) years ago. A common analogy is to imagine the earth’s history as a 24-hour clock. On this scale, the earth formed at midnight. Simple bacterial life appeared at 6 am, more complex plants and animals didn’t make it onto land until 10 pm and humans appear at one minute to midnight. Dinosaurs enter the stage at around 11.20 pm, in the Triassic period (200–250 million years ago), enjoy great success through the Jurassic (145–200 million years ago) and make their exit at 11.50 pm at the end of the Cretaceous period (66–145 million years ago). 4 Birds are dinosaurs Birds evolved from within a group of fast two-legged predatory dinosaurs called theropods, which includes such creatures as Velociraptor and T. rex. This means that dinosaurs are in fact more successful today than they have been at any other point in their history. There are nearly 10 000 living species and perhaps as many as 400 billion individual birds flitting about on the planet at any one time. As British writer Colin Tudge says, ‘The dinosaurs did not disappear when the putative asteroid struck, 65 million years ago. They are calling to us from every hedgerow’. One estimate of total dinosaur diversity (including those we haven’t yet found as fossils) puts it at around 1850 species – so, by sheer weight of numbers, the small, feathered, flying dinosaur model really has been fabulously successful. Flight opened up a whole new range of lifestyles for dinosaurs and it was a leap into the skies from which they’ve rarely looked back. Living mammal species number only about 5500, and birds outnumber them and all other groups of terrestrial vertebrates, including amphibians and reptiles.
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Before we begin
5 Ancient marine reptiles and flying pterosaurs are not dinosaurs The flying pterosaurs and the aquatic ichthyosaurs, plesiosaurs, pliosaurs and mosasaurs were large prehistoric reptiles that lived at the same time as the dinosaurs, but they were not dinosaurs. Pterosaurs were the sister group to dinosaurs and birds, and in turn all of these animals are close relatives of crocodiles (which are therefore the closest living relatives of birds). The other ancient marine reptiles are more distantly related members of the reptile group, which also includes turtles, snakes and lizards. 6 What do I mean when I say ‘dinosaur’? Since birds are simply small, specialised, mostly flight-capable forms of dinosaur, this presents a problem for how to define the rest of the dinosaur group. Officially, everything we would traditionally have thought of as a dinosaur is a ‘non-avian dinosaur’, but that’s one ugly mouthful, so in this book you can assume that when I say ‘dinosaur’ that’s usually what I mean. 7 What defines a bird? It used to be easy to define a bird: birds had feathers and beaks, they flew, they were bipedal, they laid eggs, they were warmblooded and quick-witted, and they had wishbones. The problem is that most of the 30 or so once-defining features have quite literally gone the way of the dinosaurs. Of course, birds still have all these things, but now we know that many dinosaurs had them too. So what now defines a bird? In some ways the distinction between birds and dinosaurs is arbitrary. Mike Benton, a palaeontologist at the University of Bristol in the United Kingdom, says that powered flight and a wing that was large enough to achieve it, is the one remaining thing that separates Archaeopteryx, the ‘first bird’, from its dinosaur relatives, but it may be only a matter of time until other dinosaurs are found that had powered flight too.
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8 Dinosaurs didn’t all live at the same time Compared to the very brief tenure of humans on this planet, dinosaurs ruled the roost for an extremely long time. The earliest recognised dinosaur is a bipedal labrador-sized animal called Nyasasaurus, which was named after Lake Nyasa in Tanzania (today called Lake Malawi). The fossil was collected in the 1930s but languished for many decades in a drawer at London’s Natural History Museum. A reappraisal of it in 2012 found it to be up to 247 million years old, making it significantly older than any other known dinosaur (assuming it really is a dinosaur – the remains are very incomplete). From these somewhat diminutive beginnings in the early Triassic, dinosaurs went on to great peaks and troughs of diversity in the late Triassic and through the Jurassic, before slowly declining in species numbers towards the end of the Cretaceous, when something cataclysmic finished them off 66 million years ago. A 180-million-year run really isn’t a bad innings. During this period, individual dinosaur species were continuously going extinct while other new ones were evolving. 9 Birds and dinosaurs did live at the same time The first bird, or at least one of its fairly close relatives, was an animal called Archaeopteryx, which lived in the Late Jurassic around 150 million years ago. Non-avian dinosaurs didn’t disappear until 66 million years ago, so we know that birds and dinosaurs coexisted for at least 85 million years. For a long time we had very few early bird fossils, but large numbers of exquisitely preserved fossils from China are now showing that a diverse assemblage of dinosaurs and birds shared the same habitat there during the Early Cretaceous period.
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