The series starts in North Africa, where two of the world's biggest predators once battled for supremacy. At 13m and seven tonnes, the carcharodontosaurus was a huge beast, a gigantic lizard-like carnivore with shark-like teeth over six inches long. It was an efficient hunter that would slash at its prey until it bled to death. But the discovery of an upper jaw in Morocco revealed an even bigger carnivorous killer - spinosaurus. Four metres longer than Tyrannosaurus rex, spinosaurus is thought to have been one of the biggest killers to ever walk the Earth. But unlike the meat-eating carcharodontosaurus, spinosaurus mainly ate fish, living and hunting almost exclusively in the water. Like all predators that share an environment, the two may once have had to compete for food. Planet Dinosaur takes a look at what one such deadly battle may have looked like and finds out which giant beast would have been most likely to survive a fight to the death.