"THEY GROWL" "We're living through THE golden age of dinosaur discoveries." "All over the world, a whole new generation of dinosaurs has been revealed." "From the biggest giants... and the deadliest killers... to the weird and wonderful." "From the Arctic to Africa." "From South America to Asia." "In just the last few years, we have uncovered the most extraordinary fossils, exquisitely preserved and tantalisingly intact." "Combined with the latest imaging technology, we have been able to probe deeper and reveal more than ever before." "It gives us our first truly global view of these incredible animals." "In this programme, we're exploring the lost world of Africa." "For almost 100 years, this was a forgotten land." "Now, new discoveries have revealed some of the most spectacular dinosaurs ever found." "Two giant killers, both bigger than T Rex, both living in the same place." "IT ROARS" "One of these killers, more than any, has captured the imagination." "A bizarre killer that we've only just managed to reconstruct, in the last few years." "The story begins in Egypt, in 1912, when fragments of a giant dinosaur were discovered." "A predator with two-metre-long spines rising over its back." "It was unlike anything seen before." "It was only in 2005, when a complete upper jaw was found, that we could accurately reconstruct this bizarre creature." "With a skull almost two metres long, this dinosaur was a colossal 17 metres from nose to tail - four metres longer than T Rex." "The reign of the dinosaurs began almost 250 million years ago." "But this killer didn't appear until a time known as the Mid-Cretaceous." "95 million years ago, its home in north Africa was a desert surrounding a vast system of rivers and swamps." "The swamps are refuges for many large dinosaurs, like the duck-billed Ouranosaurus." "IT BARKS" "IT BELLOWS" "They're also the hunting grounds for a killer." "IT BELLOWS" "IT ROARS" "IT SNIFFS AND GRUNTS" "IT SNIFFS" "IT BELLOWS" "At seven metres and three tonnes, Ouranosaurs are big..." "..but easily within the scope of a large predator." "IT BELLOWS" "IT GROWLS" "WATER SPLASHES" "IT BELLOWS" "IT SNIFFS" "Spinosaurus." "At 17 metres, the biggest killer ever to walk the Earth." "An 11-tonne colossus." "IT RASPS AND GROWLS" "However, for the time being, these Ouranosaurs are off this killer's menu." "Spinosaurus is part of a family of dinosaurs that are relatively newly-discovered." "Recent finds have shown that this strange group lived from South America, through Europe, to Asia." "But the last and biggest of all came from north Africa." "Spinosaurus itself." "In 2010, analysis of their bones and teeth revealed something surprising." "Chemical traces found in the fossils suggested the Spinosaurus lived more like a crocodile than other land-based dinosaurs." "It showed that they spent a large part of their lives in water." "IT BARKS" "Spinosaurus is a predator, but one that hunts in water." "It's ichthyophagous - a fish-eater." "This is Onchopristis." "An eight-metre-long giant swordfish, similar to those alive today." "The saw-like rostrum is lined with lethal barbs, and is in itself up to 2.5 metres in length." "It's thought they migrated into freshwater rivers to breed, where the young may be safer, but the adults are exposed to new threats." "With their breeding season at its height, these rivers are filled with Onchopristis." "It's the perfect hunting opportunity for Spinosaurus." "Spinosaurus's conical teeth evolved to grip prey rather than tear off flesh." "For that, it needs powerful arms and claws." "IT GROWLS" "GROWLING" "With prey plentiful, Spinosaurus can afford to be wasteful." "A fact which other dinosaurs take full advantage of." "Rugops, an eight-metre carnivore." "Anywhere else, it might dominate." "But here, it is dwarfed by Spinosaurus." "Spinosaurus is unique, with long, narrow jaws and nostrils set high on its head." "Its teeth were straight and conical." "They gave us a clue as to how it killed." "More evidence came in 2008, when Spinosaurus' skull was put through a CT scanner." "It revealed a curious pattern of holes and sinuses in the snout that looked just like those of crocodiles." "It's thought these contained pressure sensors, sensors that, like a crocodile, can detect prey, making it perfectly adapted to hunting in water." "This discovery gives us our best evidence of exactly how it hunted." "Able to hold its snout in the water because of its high nostrils, it can strike without even seeing its prey." "GROWLING" "IT GRUNTS" "The ever-attendant Rugops has a weak jaw and skull." "It's no killer." "It is a natural-born scavenger, living off the scraps of this highly-efficient predator." "We can assume so much about the diet of Spinosaurus because its fossilised teeth are commonly found with the remains of the giant sawfish." "More recent discoveries appear to provide even more direct evidence." "In 2005, a Spinosaur fossil was found with a sawfish vertebrae stuck in a tooth socket." "Another, discovered in 2008, had a fragment of a sawfish barb apparently embedded in its jaw." "They suggested a clear predator-prey relationship." "Spinosaurus is the region's biggest killer because it can exploit an environment so successfully." "A dinosaur at home in water." "For a time, it lived with little threat from other dinosaurs and the species evolved into a 17-metre giant." "But Spinosaurus wasn't the only giant predator which thrived here." "Carcharodontosaurus." "Land-based killer." "A meat-eater." "A carnosaur." "A cousin of Allosaurus, but four times bigger." "With serrated teeth 16 centimetres long," "Carcharodontosaurus was a giant killer." "Up to 13 metres long and weighing around seven tonnes." "Like Spinosaurus, it too was bigger than T Rex." "Big predators need big hunting ranges." "Carcharodontosaurus may have needed up to 500 square kilometres each, making competition for the best hunting grounds intense." "IT ROARS" "These young, male Carcharodontosaurus both want supremacy over this territory." "Dominating the land is the key to survival for these killers." "That can mean a fight to the death." "THEY GROWL AND ROAR" "THEY PANT AND GROWL" "THEY GRUNT AND SNORT" "IT ROARS" "The evidence of in-fighting between carnivores of the same species is dramatic." "Forensic examinations of fossils has uncovered injuries on the skull bones of many large carnivores." "Tooth puncture marks and gouges are remarkably common." "Such violent head- and face-biting is thought likely to be territorial." "With so much to gain, fights over prime hunting territory would be commonplace." "For this victorious Carcharodontosaurus, the prize is the hunting rights to these Ouranosaurs." "Not an easy prey to catch, even for the fastest of predators." "But we think Carcharodontosaurus has a hidden advantage." "In 2008, detailed bone analysis suggested these dinosaurs employed a system of air sacs." "Air sacs are used in breathing." "They ensure that oxygen-rich air flows continually through the lungs when breathing in and out." "It's a very efficient system, similar to that of birds." "It implied that dinosaurs like Carcharodontosaurus were highly-active hunters." "And they needed to be." "It's reckoned that a dinosaur of this size would need to eat a minimum of 60 kilos of meat every day simply to survive." "Big hunters rely on ambushing their prey." "Closing as much distance between it and its chosen victim." "HONKING" "SQUEALING, GROWLING" "IT MOANS" "LOW GROWLING" "This Carcharodontosaurus doesn't waste energy chasing the injured animal." "Its initial attack has critically wounded the Ouranosaurus." "Now, it simply needs to follow and wait." "PANTING" "Carcharodontosaurus were deadly killers, but not in the way you might expect." "Its skull was relatively weak." "And computer analysis has shown that they're unlikely to be strong enough to hold onto struggling prey." "Their teeth were thin, like knives, too weak to bite easily through bone." "But they were sharp, with deadly serrations, just like a shark's." "The very name Carcharodontosaurus means "sharp-toothed lizard"." "We think it used its skull and teeth to slash deep into the flesh of its prey, causing massive injury and blood loss." "Delivered at speed, such an attack could kill without the need for an intense struggle." "It's an efficient killing method and one that's perfectly suited to this environment." "But success can look very different when a season changes." "For a time, Cretaceous north Africa had two deadly killers." "By exploiting different environments, they didn't compete and could coexist, dominating their chosen habitats." "Spinosaurus was a specialist." "But this came with risks." "Small environmental changes can make it vulnerable." "And this area is prone to seasonal droughts." "When the river is dry," "Spinosaurus' usual food supply has disappeared." "Other animals retreat to a few remaining pools." "Some, the Spinosaurus would do well to be wary of." "The smaller crocs aren't the problem." "Sarcosuchus a giant 12-metre crocodile." "IT ROARS" "Reptiles like these can survive droughts by effectively hibernating during times of hardship." "Spinosaurus can't." "As an active hunter, its metabolism demands a regular supply of food." "Although it is a specialist, it isn't confined to the rivers." "In tough times, it too can hunt on land." "SQUAWKING" "IT BARKS" "SQUAWKING" "ROARING" "SQUEALING" "IT GROWLS" "Spinosaur fossils from other parts of the world have given us more details about their diets." "In 2004, a dramatic fossil was recovered from Brazil." "Part of the neck of a Pterosaur." "Embedded within one of the vertebrae was a tooth." "It was the unmistakable shape of a Spinosaur tooth." "The stomach contents of another Spinosaur, Baryonyx, from England, was found to contain some bones of a juvenile Iguanodon, a plant-eating dinosaur." "In spite of their specialisation, clearly Spinosaurs weren't exclusively fish-eaters." "But hunting and catching prey isn't easy." "Particularly when they're already alert." "IT SNIFFS" "Hunting on land," "Spinosaurus is also forced into direct competition with any large predators living in the same environment." "And here, that can only mean one animal..." "..Carcharodontosaurus." "GROWLING" "IT GROWLS" "GROWLING" "Contests over carcasses are common." "But outcomes of such fights are far from guaranteed." "Risk of injury for big animals is acute." "Modern Komodo dragons are often killed in fights over carcasses." "ROARING, GROWLING" "More than three metres longer," "Spinosaurus has size and power on its side." "ROARING, GROWLING" "But Carcharodontosaurus has the more lethal bite." "SHRIEKING" "IT GROWLS" "This time, the Spinosaurus triumphed." "But the balance of power between these two deadly killers is a precarious one." "LOW GROWLING" "In 2008, a Spinosaurus vertebra was recovered." "Part of the tall, neural spine of the bone was broken off." "It appeared to have been bitten in half." "It's been suggested that the bite was inflicted by Carcharodontosaurus." "Spinosaurus was the last and the largest of the fish-eating dinosaurs." "But ultimately, these specialists were doomed." "Something way beyond their control caused their downfall." "94 million years ago, the climate changed." "Global sea levels began to rise." "The swamps and rivers that Spinosaurus thrived in gradually were lost." "With their loss," "Spinosaurus's specialism became a vulnerability." "And the biggest predator ever known to have walked the Earth disappeared." "Subtitles by Red Bee Media Ltd" "E-mail subtitling@bbc.co.uk"