Ingentia prima, which means "the first to be huge" in Latin, lived some 237 million to 201 million years ago in what is now Argentina. The newly discovered fossils make revelations about the evolving of the giant ones many million years ago than thought of.
What is really unexpected is that the lessemsaurids achieved their huge bodies independently of the big sauropods like Brontosaurus and Diplodocus, which did indeed evolve later during the Jurassic. The new find shows it happened in less than half that time.
The plant eater, described in Nature Ecology and Evolution, is an ancestor of its titanosaur cousins Brachiosaurus and Diplodocus, renowned for their enormous necks and tails. Gigantism evolved in most of the dinosaurs, especially herbivores, providing them with protection against carnivores. The flying ones or the ones moving about on land, the earliest creatures on the planet have been a subject of keen interest to scientists. To turn into towering behemoths, it was believed the development of straight legs for support and continuous, rapid growth were essential.
Ingentia prima was big - up to 32 feet (10 meters) long - but not almost as large as the massive titanosaurs that lived millions of years after it.
Ingentia Prima would have lived in what is now Argentina, but was then the southeast corner of the supercontinent Pangaea.
Its size would also have put it at less risk of being eaten by the many flesh eating dinosaurs that were already around.
Baldetti, and her colleagues found that this was not the case, studying the remains of a unique dinosaur that her team found in the Central part of Argentina, in the province of San Juan. "That's the surprise", said Cecilia Apaldetti, a government and San Juan University researcher, according to AFP.
"These findings show that there is more than one way to "create" a giant dinosaur and that the iconic sauropods have a long history of evolutionary innovation behind them", said the scientific paper.
Researchers also reported the creature featured a bird-like cervical sac and a neck with characteristics that allowed the oversized animal to stay cool.
'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'.
Not only is the discovery important because it becomes the oldest registered dinosaur, but hints at how sauropods - the dinosaur breed with a long neck, long tail, small heads, and four thick, pillar-like legs - got so big. At the end of the Triassic period it was a type of savannah.