Researchers have always maintained that Triassic dinosaurs were small, chicken-sized critters and that it was not until the Jurassic period — about 180-million years ago — that massive herbivorous sauropods, like the Diplodocus and Brachiosaurus, emerged. However, the discovery of a new dinosaur species in Argentina suggests that the animals achieved gigantism during the late Triassic period, about 30 million years earlier than previously believed.