Argentine paleontologists declared on Wednesday that they had found a sprawling "Jurassic Park" of dinosaur fossils in the heart of Patagonia they dubbed "possibly the most significant find ever".The find in the province of Chubut, on an arid plateau some 950 miles south of Buenos Aires, includes four unknown species of dinosaurs from the Jurassic period around 150-160 million years ago, one of the world's oldest known mammals and a host of fossils of reptiles and ancient sea turtles.