Arid, rocky region with their lack of soil and plant cover are ideal for fossilhunting. Remains of any dinosaurs, prehishistoric mammals, and other long gone creatures are regularly discovered in modern deserts such as the Gobi the patagonian Desert, and the Kalahari. A major expedition of the 1920s visited the rocks there are far too ancient, being formed long before even our most distant apelike ancestors existed on earth. What the paleontologists did find were the fossils of many dinosaurs, including the pack-hunting veloclraptor, which walked upright on its long rear legs; the four-legged, pig sized horned dinosaur protoceratops, along with fossil evidence of its nests and eggs; and the low lizardshaped psittacosourus with its parrotlike peak. In recent years many asbounding fossil discoveries have been made in the dry lands of Argentina, including one of the earliest dinosaur, Herrerasaurs, which had long hind legs and sharp teeth; and one of the biggest, perhaps weighing 100 tonnes (98 t), Argentinosaurus.