Before this discovery, it was thought that gigantism developed during the Jurassic period, around 180 million years ago.
Introducing Ingentia prima, a large, four-legged, long-necked dinosaur that lived a whopping 47 million years before giants like Diplodocus and Brontosaurus shook the Earth. The authors say many of these adaptations were not specific to gigantism, instead allowing for greater mobility as I. prima moved across the Triassic landscape.
Researchers said the dinosaur - named Ingentia prima, meaning "the first giant" - was up to 33 feet (10 meters) long and weighed about 10 tons, living about 210 million years ago during the Triassic Period. Paleontologists figured that many, if not most, of the characteristics required for bodies in excess of 10 tons emerged during the early Jurassic, but the incomplete fossil record has clouded the details of this critical evolutionary stage.
The team also found biological evidence for just how the creature managed to get so big so early.
Dr Apaldetti said the climate would have been warm, with periodic monsoons. producing an African savannah style landscape, with plenty of shrubs on which Ingentia prima would feed.
Its size would also have put it at less risk of being eaten by the many flesh eating dinosaurs that were already around.
For most dinosaurs, gigantism proved to be an evolutionary survival tool, especially among herbivores who could use their size as a form of defence against predators.
Every discovery of dinosaur remains sheds new light on their evolution, but this discovery in Argentina could alter the way paleontologists see the entire evolution of dinosaurs.
Excavators found several vertebrae from the neck and tail as well as fore and hind leg bones. I. prima grew via a combination of very fast growth spurts and bird-like lungs able to supply large amounts of oxygen and keep an huge body cool, scientists report in Nature Ecology & Evolution.
"In addition, this kind of breathing implied the presence of cavities, or deep holes, in their bones - known as a pneumatic skeleton - that lightened the weight and would have favoured a large body size". However, unlike the diplodocus and other later sauropod relatives, lessemsaurids stood on bent legs and had bones which grew in short, accelerated bursts. It belongs to a group of dinosaurs known as sauropods, which includes some of the largest land animals ever known to have existed.