Subscribe and 🔔 to the BBC 👉 https://bit.ly/BBCYouTubeSub Watch the BBC first on iPlayer 👉 https://bbc.in/iPlayer-Home At 9 metres and 1.5 tonnes, Allosaurus was a formidable Jurassic hunter. But its bite was surprisingly weak - so how did it make a kill? This episode focuses on the Jurassic period, a time when the first giant killers stalked the Earth and lurked in the seas - and the slightest advantage meant the difference between life and death. In North America, the iconic allosaurus, an ambush hunter with a lethal bite, dominated. Not even the heavily armoured stegosaurus was safe from this killer, and incredible evidence reveals a glimpse of a vicious battle between these two giants. Life in Jurassic oceans was no easier - in 2008, a fossil was dug out of a frozen island high in the Arctic. It was a colossal marine reptile, twice as big as most ocean predators at 15 metres long and weighing about 45 tonnes. This was Predator X. Its skull alone was nearly twice the size of a Tyrannosaurus rex's, and its bite force unmatched by anything in the Jurassic seas. Planet Dinosaur | Episode 4 | BBC One #bbc #PlanetDinosaur All our TV channels and S4C are available to watch live through BBC iPlayer, although some programmes may not be available to stream online due to rights. If you would like to read more on what types of programmes are available to watch live, check the 'Are all programmes that are broadcast available on BBC iPlayer?' FAQ 👉 https://bbc.in/2m8ks6v.