Archeologists Rethinking Triassic Period Because of Massive Dinosaur Bones

Ingentia prima

A rendering of an Ingentia prima is seen in this handout image

However, the earliest examples of this group were small, bipedal creatures.

The dinosaur - named Ingentia prima, meaning "the first giant" - was the size of a double-decker bus, weighed about 10 tonnes, and lived around 210 million years ago during the Triassic Period.

With this discovery, researchers are now rethinking the evolution of dinosaurs, as they previously believed giant dinosaurs didn't exist until 25 million years later.

Before this discovery, it was thought that gigantism developed during the Jurassic period, around 180 million years ago.

Palaeontologists figured that many, if not most, of the characteristics required for bodies in excess of 10 tonnes emerged during the early Jurassic, but the incomplete fossil record has clouded the details of this critical evolutionary stage. We found a shape, the first giant one among all the dinosaurs.

Unlike later sauropods, Ingentia's legs were not pillar-like and its neck was shorter. To turn into towering behemoths, it was believed the development of straight legs for support and continuous, rapid growth were essential.

Dr Apaldetti said the climate would have been warm, with periodic monsoons. producing an African savanna style landscape, with plenty of shrubs on which Ingentia prima would feed.

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.

I. prima was also found alongside three specimens of an already known species called Lessemsaurus sauropoides.

The remarkably preserved specimens were discovered in a dinosaur "nest" unearthed at a World Heritage site known for its fossils in Argentina's north western San Juan province.

The remains included shoulder blades, cervical vertebrae and bones from the forelimbs, feet and skull of the four dinosaurs. The dinosaur had a bird-like respiratory system and air sacs in its bones that helped keep it cool.

The dinosaur's bone fragments displayed cyclical and seasonal growth, with a different kind of tissue to other sauropods, which allowed it to grow very quickly. At the end of the Triassic period it was a type of savannah.

Sauropods - the largest land animals to ever appear on Earth - came from humble beginnings.

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