2000; Patagonia, Argentina. This is dinosaur country, a land where the rocks are rich with fossils. For millions of years this peaceful land has kept a terrible secret and only now are palaeontologists uncovering the truth. New finds here in South America are revolutionising our picture of the prehistoric world. It now seems that in the time of the dinosaurs Patagonia may have been the scene of the bloodiest battle in the history of life, one that matched the biggest animal ever to have walked the Earth against a new dinosaur, the most fearsome killer that ever evolved. A huge plant-eating dinosaur takes on a massive carnivore in an ugly pitched battle for survival. This idea of the two biggest creatures on the planet locked in mortal combat has proved irresistible for science-fiction writers and movie makers, but for the scientists who study dinosaurs this was pure fantasy. They knew that this clash of Titans could never have happened in real life. That's because in real life the giant, long-necked herbivores never lived alongside the mega-carnivores, huge dinosaurs like Tyrannosaurus rex, the king of the meat-eaters. The two giants of their kind never walked the Earth at the same time in the same place. Creatures like these could never have met - or so the scientists thought.