Giant dinosaur bones get archeologists rethinking Triassic period

Giant dinosaur bones get archeologists rethinking Triassic period

"When we found the first remains of this dinosaur, we realized he was unique". Their distant ancestors were small, agile, two-legged dinosaurs known as prosauropods. Scientists had previously believed the first giant dinosaurs appeared roughly 180 millions years ago.

The discovery winds back the clock on the emergence of giant dinosaurs by a staggering 30 million years - shedding fresh light on their evolution.

Sauropods were the first successful group of herbivorous dinosaurs, dominating most terrestrial ecosystems for more than 140 million years, from the Late Triassic to Late Cretaceous. It was at least twice as large as the other plant-eaters that shared the warm, savannah environment it inhabited.

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. But dinosaurs weren't always giants - during the earlier Triassic period they were mostly chicken-sized critters, and they didn't really grow to be massive until the Jurassic.

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 dinosaur had an elongated neck and tail, although not on the scale of Diplodocus.

The bones belonged to an herbivore called Ingentia prima. The partial fossil, found buried within the southern outcrops of the Quebrada del Barro Formation in northwestern Argentina, consists of several neck vertebrae, a shoulder bone, and several bones from its legs and tail.

The newly identified bus-size beast - named Ingentia prima, which means "first giant" in Latin - weighed up to 11 tons (10 metric tons) and measured up to 32 feet (10 meters) long.

What is really unexpected is that the lessemsaurids achieved their huge bodies independently of the enormous sauropods like Brontosaurus and Diplodocus, which did indeed evolve later during the Jurassic. Unlike the younger sauropods, these creatures stood on bent legs and had bones that thickened through accelerated bursts instead of steady and rapid growth.

They also had the same bird like air sacs - respiratory structures which are thought to have been necessary to keep large animals cool.

"It is a new way to get body size in an early moment in evolutionary history", said Dr Apaldetti. These eventually evolved into the four-legged creatures that became the largest animals that ever walked the land.