"946)}(GROWLING)" "863)}JOHN HURT:" "We are living 943)}through a dinosaur revolution." "862)}We have pushed the boundaries of 943)}our knowledge further than ever before." "946)}(ROARS)" "943)}We have a completely new understanding 862)}of the greatest killers" "938)}ever to walk the Earth." "946)}(GROWLING) 857)}has become the icon" "943)}of these new predators." "with two-metre-long 943)}spines rising over its back." "943)}It was unlike anything seen before. 862)}that we could accurately reconstruct" "938)}this bizarre creature. 857)}this dinosaur was a colossal 17 metres" "938)}from nose to tail." "943)}Four metres longer than T-Rex." "862)}The reign of the dinosaurs began 862)}but this killer didn't appear until" "938)}a time known as the mid-Cretaceous. 938)}its home in North Africa" "862)}was a desert surrounding 943)}a vast system of rivers and swamps." "862)}The swamps are refuges 938)}like the duck-billed Ouranosaurus." "946)}(SQUAWKS)" "946)}(CALLING)" "862)}They are also the hunting grounds 938)}for a killer." "946)}(CALLING)" "946)}(GROWLING) 862)}the biggest killer" "938)}ever to walk the earth." "938)}An 1 1-tonne colossus. 857)}these Ouranosaurs" "938)}are off this killer's menu." "862)}Spinosaurus is part of a relatively 943)}newly discovered family of dinosaurs." "862)}They've been found in South America Siamosaurus." "862)}But the last and biggest of all 938)}came from North Africa:" "943)}Spinosaurus itself." "857)}And studies of their bones and teeth 943)}revealed something amazing. 938)}but one that hunts in water." "944)}Spinosaurus is unique." "narrow jaws and nostrils 862)}and it had a curious pattern 943)}which give us a clue to how it hunted. 943)}eight-metre-long giant sawfish." "a Spinosaurus skull 943)}was put through a CT scanner." "857)}It revealed that the holes 938)}and sinuses in the snout" "944)}looked just like those of crocodiles." "862)}It's thought these contained 950)}pressure sensors. 943)}can detect the movement of prey." "857)}It can strike 943)}without even seeing its victim." "this eight-metre Rugops 943)}might be the top carnivore. 862)}a predator that adapted to exploit" "943)}an environment so successfully 943)}it evolved into a 17-metre giant." "862)}Spinosaurus is the biggest 128)}but it wasn't the first giant killer." "128)}The first giant killer dinosaurs 209)}appeared much earlier. 209)}1 50 million years ago. 123)}from the Morrison Formation" "204)}in North America." "128)}Yet it's only recently that 204)}we have been able to work out" "943)}how these predators hunted." "946)}(WIND HOWLING)" "946)}(SNUFFLING) 857)}Allosaurus is the most common killer" "938)}in these lands." "with a battery 938)}Allosaurus is a formidable hunter." "862)}A lone Camptosaurus 943)}should be an easy kill." "857)}Allosaurus teeth were serrated 862)}perfectly evolved" "943)}for tearing through flesh." "recent research has indicated 857)}that Allosaurus's bite was" "943)}surprisingly weak." "862)}Calculations suggested its bite 943)}was less powerful than a lion's." "863)}So just how did thisJurassic monster 938)}hunt and kill?" "946)}(SQUEAKS NERVOUSLY)" "862)}Camptosaurus relies on its keen senses 943)}to avoid predators. 943)}is a fast and powerful ambush hunter." "946)}(ROARING)" "946)}(GROANING)" "946)}(MOANING WEAKLY) 946)}(ROARING)" "862)}Despite the apparent 943)}have a deadly killing method." "857)}Its skull could withstand a force 943)}more than 1 5 times as great as its bite." "857)}This meant that Allosaurus 862)}its strong neck muscles" "944)}driving its top jaw into its prey." "the serrated teeth 943)}would tear through its prey's flesh..." "862)}the victim dying through 938)}a combination of shock and blood loss." "946)}(ROARING) 943)}Saurophaganax." "it is the biggest 943)}carnivore in the region." "946)}(ROARING)" "946)}(BOTH ROARING) 943)}One of the advantages of being so big" "862)}is that stealing another's kill 938)}is that much easier. 128)}and their spread 128)}smaller dinosaurs needed new strategies" "209)}if they were to survive. 204)}China has been the focus" "123)}of some remarkable fossil discoveries." "128)}One extraordinary fossil hints 128)}how some may have avoided" "204)}these killer dinosaurs." "129)}It lived in the Jurassic forests 209)}of China 1 54 million years ago." "862)}Hiding in these lush forests 943)}is Epidexipteryx. 943)}and being small makes it vulnerable." "946)}(DISTANT ROARING)" "943)}This is Sinraptor." "943)}A small dinosaur like Epidexipteryx 857)}would be of no interest" "938)}to a seven-metre adult." "944)}But this is a juvenile." "946)}(ROARING)" "943)}Being small does have its advantages." "943)}Everything we know about Epidexipteryx 857)}comes from an incredible fossil" "938)}first revealed in 2008." "857)}It showed an animal with a small skull 943)}and large eye sockets 862)}with toes suited to gripping branches" "943)}and very long arms and hands." "862)}It suggests that this was a dinosaur 943)}well suited to living in the trees." "862)}The extraordinary 943)}elongated third finger" "857)}is another distinctive 943)}feature of the group." "857)}With this 862)}Epidexipteryx has the perfect tools" "938)}to hunt for insects." "946)}(INSECT BUZZING)" "which is is quite a prize." "862)}A prize that can attract 938)}unwanted attention." "Epidexipteryx." "946)}(SQUAWKING)" "946)}(BOTH SQUAWKING)" "862)}There is more to this extraordinary 943)}creature than first meets the eye." "938)}The fossil has also revealed 857)}that it was covered simple feathers." "128)}Feathers that were likely 210)}to have evolved for just one reason:" "943)}to keep it warm." "943)}But there is one last striking feature:" "943)}four long feathers on its tail." "857)}These feathers aren't like those 938)}of modern birds. 943)}almost certainly only for show." "862)}They're the earliest record 938)}of ornamental feathers." "the very name "Epidexipteryx 943)}means "display feather"." "946)}(SQUAWKING)" "862)}And they're among the most bird-like 943)}of any dinosaur." "862)}Only in the trees can you be safe 943)}from large predators like Sinraptor." "862)}Moving into the trees opened up 943)}an entirely new world for dinosaurs." "862)}And it wasn't long 938)}before killers followed. 857)}lived in northeast China 128)}at the beginning of" "209)}the Cretaceous period." "128)}A dinosaur that took tree-living 204)}to a whole new level." "943)}This is Xianglong. 943)}predators were sure to follow." "944)}Microraptor." "and well adapted 943)}to chasing prey in the canopy." "has a trick." "943)}This is a flying lizard." "862)}And the exquisite fossils of Microraptor 943)}revealed a surprise." "857)}The feathers of this dinosaur or for show." "862)}Their structure is plainly visible 938)}from the fossils." "veined 862)}their shape creates" "943)}a perfect aerodynamic surface." "862)}And they aren't confined 938)}to its forearms." "had long feathers." "862)}These feathers are designed 943)}for one thing only:" "943)}flight." "862)}Microraptor is a four-winged dinosaur 938)}that took to the skies." "862)}But Microraptor isn't the only 943)}flying monster here." "more than capable 943)}of stealing prey." "943)}But it has a bigger prize in mind." "946)}(GROANS)" "857)}And Sinornithosaurus 943)}has a deadly secret." "a study of Sinornithosaurus 862)}found distinctive grooves" "943)}along the length of its teeth." "862)}They resemble those of 862)}the grooves of its teeth used" "938)}to deliver venom into its victim." "857)}The team even identified 943)}what they thought" "123)}was the location 204)}of the venom sack in the fossil." "862)}It appeared Sinornithosaurus 943)}could kill with poison." "862)}Having longer flight feathers 943)}Microraptor is by far the better glider. 943)}the only way is down." "862)}Microraptor's long feathers mean much less run." "943)}Sinornithosaurus has no such problem. 938)}the tables are turned." "943)}Microraptor has a fortunate escape." "857)}Killer dinosaurs dominated 938)}and had even taken to the air." "862)}But by the middle of the Cretaceous things were changing." "943)}A new breed of killers was emerging." "943)}These were the famed Tyrannosaurs." "857)}Formidable hunter-killers that 943)}swept aside almost all other predators." "857)}Carnivorous dinosaurs that remained 943)}sometimes going to extreme lengths." "862)}One such group was 938)}the bizarre Therizinosaurs." "the most complete skeleton 938)}found so far was described." "857)}It lived in New Mexico 943)}92 million years ago." "946)}(GROWLING) 943)}a mid-sized Tyrannosaur." "862)}And they're also home 943)}Nothronychus." "862)}It's actually a close relative 944)}but with one major difference." "943)}Nothronychus has given up eating meat." "946)}(GROWLING)" "946)}(ROARING)" "857)}Therizinosaurs had been 943)}known only from tantalising fragments." "862)}That all changed with 943)}the discovery of Nothronychus." "862)}It gave us our clearest look 943)}at this strange group of dinosaurs. 943)}it had wide hips and a long neck." "856)}Its teeth showed that 938)}these weren't the teeth of a killer." "857)}Far from its ferocious 862)}this pot-bellied dinosaur" "943)}had evolved into a strict vegetarian." "862)}But armed with viciously long claws 943)}it was by no means defenceless." "946)}(GROWLING) 943)}Nothronychus has easy access to food." "946)}(GROWLS)" "943)}Nothronychus thrives here 862)}because it doesn't compete" "943)}with the Tyrannosaurs." "863)}But just because 943)}you're not competing for food" "943)}doesn't mean you're not seen as food." "946)}(GROWLING) 943)}getting bigger and more deadly." "862)}They developed 943)}into the ultimate predators" "862)}and dominated virtually 938)}all of Asia and North America." "123)}The most famous of these 129)}but it was just the last" "209)}in a long line of giant killers. 938)}North America was home 943)}Daspletosaurus." "857)}Its effectiveness as a killer 943)}is clear from its anatomy." "strong skull muscular neck." "862)}Forward-facing eyes make 943)}tracking moving prey easy. 938)}it's all about the bite. 857)}with a bite force unmatched" "943)}by any other dinosaur in the region." "857)}This is a killer in a 943)}completely different league." "946)}(GROWLING)" "946)}(ROARING)" "862)}This group have congregated to 943)}take advantage of an annual event." "857)}A vast herd of Centrosaurus 938)}is on the move." "they're walking 938)}towards almost certain death. 123)}thousands of bones have been discovered" "943)}scattered across the same rock layer." "862)}They belong 938)}to the horned dinosaur Centrosaurus." "862)}And they appear to be 943)}sites of wholesale slaughter." "857)}Seasonal monsoons drives 943)}away from coastal flooding." "946)}(THUNDER CLAPPING)" "946)}(ROARING) 943)}but at the expense of the few." "862)}And things are about to get worse 938)}for the Centrosaurs." "938)}With a flooded river ahead 943)}the stage is now set for a massacre. 943)}it's not the Daspletosaurus" "862)}that are responsible 943)}for the scale of the slaughter." "862)}There's an even more deadly killer 938)}at work here." "938)}The real killer is the weather itself." "857)}Recent studies 938)}of this dense bone bed indicate" "857)}that 96% of the bones" "Centrosaurus." "862)}And relatively few of the bones 943)}display any bite marks." "862)}The fossil evidence suggests 862)}the result of widespread" "943)}seasonal flooding." "862)}An event that we have seen repeated 938)}in over 20 different sites. 944)}new opportunities emerge." "946)}(SCREECHING) 943)}Daspletosaurus's authority is absolute." "862)}Tyrannosaurs' domination of the globe 943)}might have been total" "862)}had it not been for a strange quirk 943)}in the arrangement of the continents. 862)}the planet had a clear 862)}with no physical link between" "943)}the parts of the globe." "862)}It meant the Tyrannosaurs couldn't 943)}spread to the southern continents." "a different type of killer 943)}reigned supreme." "938)}These were Abelisaurids. 209)}Madagascar has provided" "128)}the most comprehensive evidence 209)}about these predators. 209)}Madagascar was already an island. 863)}Madagascar was subject" "943)}to devastating droughts. 943)}scavenging is the only way to survive." "946)}(INSECTS BUZZING)" "863)}We thought Majungasaurus 943)}was the top predator here. 944)}some bones of a number of Majungasaurs" "943)}were reported gouged with teeth marks. 943)}more brutal killer at large." "946)}(SQUAWKING)" "946)}(GROWLING)" "946)}(ROARING)" "857)}A carcass will attract 943)}every big predator for miles around." "946)}(GROWLING)" "944)}A male Majungasaurus." "862)}It is more than capable 943)}of challenging for the carcass." "946)}(ROARING)" "863)}This fight is about more than just 943)}winning the feeding rights to a carcass." "857)}When the bite marks 944)}on the mauled Majungasaurus remains 123)}the marks on the bones" "204)}were found to match 944)}Majungasaurus itself." "857)}This is the first irrefutable evidence 938)}of dinosaur cannibalism. 943)}but it's a behaviour that clearly shows" "857)}the most successful killers 943)}will exploit any situation" "943)}to their maximum advantage." "862)}Killer dinosaurs' ability to adapt 943)}was exceptional." "862)}It meant they were able to colonise 943)}continually evolving and changing." "857)}Their dominance of life on Earth 938)}was absolute." "943)}Yet they were doomed." "862)}Their downfall was caused by 943)}an asteroid smashing into the Earth." "862)}Travelling 20 times faster 938)}it slammed into the Gulf of Mexico." "862)}The impact released more energy 938)}than a billion atomic bombs. 943)}massive earthquakes and tsunamis." "862)}But most devastating was the material 943)}blasted high into the atmosphere." "862)}This shrouded the planet in a cloak 943)}cutting off sunlight." "857)}The Earth was thrown 943)}into almost permanent night." "938)}Animals that survived the blast 857)}were now faced 128)}as a devastating chain of events" "204)}was set in motion." "many plants died." "857)}Plant eaters are 938)}the first to be affected." "862)}Fresh growth of plants offers 862)}allowing the smallest" "943)}to scratch out a living." "862)}But these aren't enough 943)}to sustain anything for long." "946)}(SCREECHING)" "946)}(SCREECHING)" "862)}Scavengers initially have 938)}an easier time of it." "946)}(SQUAWKING)" "943)}But this surplus is an illusion." "too." "862)}The impact resulted in the collapse 938)}of whole food chains." "857)}And the extinction 944)}didn't just affect dinosaurs." "128)}Virtually all life on Earth 204)}was affected." "128)}More than 60% of all species 209)}were wiped out." "128)}Yet the extinction wasn't a lottery." "862)}One factor more than any other 938)}determined the dinosaurs' fate:" "938)}size." "no animal weighing 943)}more than 25 kilograms survived." "863)}There just isn't enough food 943)}to sustain large animals." "it's the very thing 938)}that makes dinosaurs so iconic" "938)}that condemns them to extinction."