Double-decker dinosaur fossil find makes scientists rethink evolution of Jurassic giants

However, it is unclear how dinosaurs grew to such massive proportions. I. prima lived about 215 million years ago, a good 47 million years before its long-necked cousins, including Brachiosaurus and Diplodocus, existed, the researchers said.

The animal used a novel strategy to become super-sized, involving very fast growth spurts and efficient bird-like lungs, say palaeontologists.

She and her team discovered the remains in the San Juan province in 2015.

The findings, presented in a published on Monday in the journal Nature Ecology and Evolution, introduces this dinosaur species as Ingentia Prime (First Immense) and is described as one of the first giant sauropods. This creature, named Ingentia prima, "first giant" in Latin, was more like its anatomy in the later sauropods than on his contemporaries. However, Ingentia prima inhabited the Earth in the late Triassic period, somewhere between 210 and 205 million years ago.

They stretched to 130 feet (40 metres) and weighed up to 80 tonnes (80kg). But its discovery is a surprise, coming so early in dinosaur evolution.

Apaldetti called Ingentia not only the largest dinosaur but the biggest land animal of any kind up to that point in time.

Large size, scientists believe they began to be achieved only in the middle and at the end of the Jurassic period, about 180-155 million years ago, when the first neosauropods, including Diplodocus, argentinosaurus and all of the largest dinosaurs of that era. The remarkable discovery of four lessemsaurid skeletons forces us to rethink when, and how, dinosaurs got so huge. Cyclic growth was common in the dinosaurs of that period, but they usually stopped growing until they reached nearly 1.8 tons in weight and 3 meters in length.

Experts believe this period was a pivotal stage in the history of dinosaurs but the fossil record is very incomplete.

The researchers found that the weight of I. prima ranged between seven and 10 tons, and showed elongated neck and long tail albeit not as pronounced as those seen in their later relatives. It was about 10m long.

Researchers also reported the creature featured a bird-like cervical sac and a neck with characteristics that allowed the oversized animal to stay cool. Together, these dinosaurs belong to a sauropod subgroup known as the lessemsaurids, which lived between 237 and 201 million years ago (relatively soon after dinosaurs first appeared) in what is now Argentina but was then the southeast corner of the supercontinent Pangaea.