"Imagine you could travel back in time - to a time long before man." "Back across 65 million years." "You would see huge changes in the vegetation and the climate." "Even the surface of the Earth itself would move as mountain ranges are pushed up by colliding continents." "You've reached a period in Earth's history known as the Cretaceous." "It is a very different world." "The Himalayas do not yet exist and the Atlantic is only half as wide." "There is no grass, only conifer forests and fern prairies." "This is a world ruled by dinosaurs." "This is a world ruled by dinosaurs." "(Fierce roar)" "Giant reptiles like Tyrannosaurus, a five-tonne predator, stalk the land." "In Walking With Dinosaurs, we will show you how these magnificent creatures live - how they eat, fight and reproduce." "You will witness how the forces of nature conspire to drive these animals to extinction." "But this series will also take you back much further." "To the Jurassic period - when life on Earth was at its most spectacular." "(Low grumbling roar)" "(Low grumbling roar)" "The creatures here bathe in a warm tropical climate - there are no icecaps at the poles." "Flowers and broad-leaved trees are yet to evolve." "In the air and on the land, the world is dominated by reptiles, and by far the most common are the dinosaurs." "But they are not the only giants." "Huge pterosaurs rule the skies and, below them, massive marine reptiles harvest the rich oceans." "However, first, this series will go back even further, to discover where dinosaurs came from." "This is our own Earth during the Triassic period." "There are no separate continents, just one landmass called Pangaea." "It is a harsh place dominated by deserts." "The Triassic has already seen many different varieties of ancient reptiles come and go." "But now, out of this dry wilderness," "But now, out of this dry wilderness, has appeared something revolutionary." "A family of reptiles destined to shape the course of life on Earth for the next 160 million years." "These are the first dinosaurs and this is where our story begins." "First light across the western hills of Earth's only continent, Pangaea." "This world has been ruled by one group of giant reptiles for over 50 million years." "But these ancient creatures have had their day." "All over these lush fern prairies, an evolutionary battle has broken out among the newer types of reptile for supremacy of this strange world." "0n these Triassic proving grounds, dinosaurs are still rare, but they are beginning to show signs of their future success." "(Small growl)" "It is the end of the wet season and the local river is full." "But it will not remain this lush, and ahead lies nine months with no rain." "0ne type of reptile has evolved to thrive in drought." "Dinosaurs like this Coelophysis can survive on very little water." "She is also light-boned, fast, and she is beautifully adapted... for killing." "Dinosaurs appeared around 10 million years before, as small predators." "What makes them unique is special hips and ankles that allow them to stand perfectly balanced on two legs." "With lightning-fast reactions, they are built to survive." "(Loud roar)" "(Trumpeting calls)" "A chorus of calls signals the arrival of a huge herd of Placerias." "They are making their way down from the ferns for their morning drink." "These impressive one-tonne beasts are not related to dinosaurs." "They are a much more ancient type of reptile." "0nce there were many different kinds of these powerful creatures, but now the Placerias are the only ones of their kind that remain." "They are an endangered species." "Despite their fearsome appearance, they are actually gentle herbivores." "Their tusks are used for digging up roots." "(Angry growling)" "But on two angry males, these tusks can make lethal weapons." "For the swift Coelophysis, Placerias are prey." "This young female targets the old and weak in the slow-moving herd." "(Growling and trumpeting)" "0ne day, the descendants of dinosaurs like Coelophysis will take over this world, but it is their speed and agility that gives them the edge in the mid-Triassic." "Further downriver is one of the Triassic's most bizarre animals." "The cynodont is a missing link between reptiles and mammals." "As he runs, his backbone moves" "As he runs, his backbone moves from side to side like a reptile's, but he has hair and lives down a burrow, like a mammal." "Deep inside, his mate sleeps on a bed of lichen." "The bond between cynodonts is very strong - they pair for life." "Like all land reptiles, they lay eggs, but after hatching, the young are utterly dependent on their parents and for the first three months, feed from milk glands on the mother." "This form of reproduction has evolved to protect their young from the daylight predators outside." "By day, even the father sticks close to the safety of the burrow and carries out domestic chores." "He only hunts at night." "In the not too distant future, small furry mammals will evolve from reptiles like these." "In the heat of the dry season, the Placerias herd spreads out over the scrubland to feed." "(Low growling)" "Suddenly the warm breeze changes and there is the scent of fear in the air." "(Vicious growling)" "Postosuchus, a merciless ambush predator - the largest carnivore on Earth." "(Roars )" "The terrified Placerias flee, but they are desperately slow and one of them is mortally wounded." "Their tormentor is a distant cousin of the dinosaurs, but unlike them, she is too front-heavy to run on two legs." "Yet the Postosuchus is easily fast enough to keep pace with the herd." "Eventually, a combination of shock and blood loss defeats the wounded Placerias." "The carnivore's bite has done its job." "The Placerias is now too weak to fight and the Postosuchus has an easy meal." "As the weeks of the dry season pass, only the vegetation around the river remains lush and this attracts exotic hunters like this Peteinosaurus." "She is a flying reptile who has evolved extra-long fingers to support her delicate wing membranes." "(Rattling call)" "The river's resident flying predators are dragonflies." "Insects like these evolved long before the first reptiles." "0ver 100 million years ago, some took to the air and became aerial killers." "But in the Triassic era, these hunters have become the hunted." "A jaw full of needle-sharp teeth makes short work of the insect." "Peteinosaurus have evolved strong, lightweight bones for flight, and like the dinosaurs, they are fast and deadly." "Reptiles are becoming the new masters of the air." "In temperatures of over 40 degrees centigrade, the Placerias need lots of water and spend more time at the river." "But the herd is nervous." "They know this is a good place for an ambush." "The Postosuchus is not hunting." "She has recently eaten her fill and also needs to come down to the river to drink." "Six metres long, heavily built with an armoured back, she needs a huge amount of food and, therefore, has to defend a very large territory." "The only creature on the planet she fears is another Postosuchus." "(Loud, rasping roar)" "It is the middle of the dry season, months since any rain." "Across the scrubland, smaller rivers are drying out." "In one, a Peteinosaurus risks a cooling bath." "He constantly checks for danger." "The cynodonts lie secure and cool through the hottest part of the day." "But no animal here is truly safe." "The female Coelophysis has picked up the scent of their bedding." "Soon she is exploring the entrance... and she is not alone." "(Puppy-like growling)" "Clearly these dinosaurs have not met cynodonts before." "Nearby, the Placerias search for moist roots beneath the drying ferns." "The Postosuchus once again needs food." "But her last attack left her with a tusk wound on her thigh - a severe handicap for such a heavily-built creature." "The Placerias herd spots her before she can set an ambush and they mount an aggressive defence." "(Angry roaring)" "She will get no food here, and in such a competitive world, her wound may yet prove fatal." "Evening, and in the burrow, the cynodonts prepare for a night of hunting." "The young are more developed now and starting to move about the nest, but they are still vulnerable." "It'll be two months before they can do without their parents' protection." "The adult male checks the coast is clear." "An inquisitive youngster follows him to the end of the burrow." "(Squealing)" "(Cynodont barks )" "Too late, the male responds to his squealing pup." "Again, he drives the dinosaurs away, but this time, they don't go far." "Nearby, a thirsty male Postosuchus has invaded the wounded female's territory." "But this withered Triassic landscape cannot support two giant predators in one dry valley." "The female is too weak to fight." "After dominating her territory for a decade, she is driven from her home." "The male uses precious water to mark his new territory." "The male uses precious water to mark his new territory." "Meanwhile, the Coelophysis are starting to dig the cynodonts out." "Their situation is becoming desperate... as the dinosaurs will soon expose the nest." "As the sun sets, the pair have only one choice." "It means shattering their unique parental bond - they eat their own young." "This denies the dinosaurs their food and gives the cynodonts the chance of escape." "Under the moonlight, they seize the moment and abandon the hole." "In the morning, the Coelophysis are back." "They can smell the cynodonts, and it will take them time to realise their work is in vain." "The dry season continues." "After the cynodont hole, the female Coelophysis has found something in the parched river bed." "It is a lungfish, and the dinosaur's serrated teeth will make short work of its protective cocoon." "But she is not left alone to eat it for long." "Coelophysis numbers are increasing, and this leads to confrontations." "(Vicious squealing)" "The pressure of numbers also brings other changes in behaviour." "Under the merciless sun, a flock of Coelophysis has united for a kill." "The wounded female Postosuchus has lost the use of her back legs." "However, her mighty jaws could still tear a dinosaur apart." "The great carnivore's strength fails." "The great carnivore's strength fails." "All the Postosuchus's heavy armour and muscle are no more than food for the agile little dinosaurs." "Their long snouts and nibbling teeth can reach under her thick scales." "They eat her from the inside out." "The rains are late, and now the real test for survival begins." "As vast areas turn into red desert, the Placerias are driven to migrate in search of water." "But in this extreme drought, dinosaurs have a crucial advantage over other reptiles." "When they excrete, they waste very little water." "Nowhere is this advantage more obvious than by the shrunken river." "Coelophysis are gathering in huge numbers," "Coelophysis are gathering in huge numbers, and in years of hardship like this, it is the dinosaurs that win through." "There is little room for other reptiles, and without prey, the dinosaurs swiftly turn on each other." "Cannibalism is common." "The Triassic is pushing life to its limits." "Night reveals dinosaurs are not the only animals that have managed to cling on." "The cynodonts have survived their brush with death and dug another burrow hidden in some dried ferns." "0nce again, the male is hunting in the darkness." "(Growling, animal squeals)" "He has caught the only common prey - a baby Coelophysis." "(Thunder rumbles )" "(Thunder rumbles )" "After nine months of drought, at last the rains have arrived." "Soon, the thirsty scrublands are soaking." "In her burrow, the female cynodont has laid a fresh clutch of eggs." "0ne day in the future, this strategy of investing in their young will pay off for their mammalian descendants." "But as mammals evolve over the next 160 million years, they'll only survive as a few small species, clinging on at the edge of a world dominated by dinosaurs." "0utside, that future is already arriving." "The female Coelophysis has survived the drought, along with many of her kind." "But they have also been joined by another type of dinosaur." "(Low, rumbling call)" "A huge herd of Plateosaurus has been drawn to the swollen river." "It is hard to believe that these beasts are related to Coelophysis, but these are plant-eating dinosaurs." "Their size is the key to their success, and at four tonnes, they are simply too big to be threatened." "This is the shape of things to come - the age of the dinosaurs has dawned." "20 million years later, extinction wiped out thousands of species of reptile, but the dinosaurs went from strength to strength." "Carnivores grew to enormous sizes, but their prey got even bigger." "In the next programme, we meet the giants of the Jurassic."