Pliosaurs were large, extinct marine reptiles from the Jurassic Era. During this time they were the top predators of the ocean averaging from four to fifteen metres in length. The largest pliosaur fossil found was unearthed on Spitspergen, Svalbard in 2006. This immense 150 million year old specimen is characterized by its short neck, elongated head and long, powerful jaws. It differs from the long-necked plesiosaurs which are rumoured to fit the description of the mythical Loch Ness Monster.