Scientists in Argentina have discovered the earliest-known "giant" dinosaur, revealing the evolution of gigantism began around 30 million years earlier than previously thought.
The dinosaur – named Ingentia prima, meaning "the first giant" – was up to 33ft long and weighed about 10 tons, living about 210 million years ago during the Triassic Period.
The four-legged herbivore is three times the size of the largest dinosaur species discovered from the Triassic period to date.
The find, published in the journal Nature Ecology & Evolution, has prompted paleontologists to rethink the evolution of dinosaurs.
"Before this discovery, gigantism was considered to have emerged during the Jurassic period, approximately 180 million years ago, but Ingentia prima lived at the end of the Triassic, between 210 and 205 million years ago,” said paleontologist Cecilia Apaldetti of the Universidad Nacional de San Juan in Argentina, the study’s lead author.
Ingentia was an early member of a dinosaur group called sauropods, a forerunner to the largest land animals known to have walked the earth, including the Patagonian behemoths Argentinosaurus, Dreadnoughtus and Patagotitan.
Unlike later sauropods, Ingentia’s legs were not pillar-like and its neck was much shorter.
"We see in Ingentia prima the origin of gigantism, the first steps so that, more than 100 million years later, sauropods of up to 70 tons could come into existence like those that lived in Patagonia," Dr Apaldetti said.
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.
The fossil was found in the San Juan Province, in northwest Argentina during a field trip. The region has been the site of previous discoveries of creatures such as ancient turtles, iguanas as well as other dinosaur species.
The scientists found four skeletons in all, one of the new Ingentia species and three of related dinosaurs.
It was at least twice as large as the other plant-eaters that shared the warm, savannah environment it inhabited. The biggest predators there were not dinosaurs, but large land-dwelling relatives of crocodiles.
The discovery of the Ingentia has also provided further evidence for how dinosaurs were able to grow to such massive proportions – from their bone structures to highly developed breathing systems.
The researchers who examined Ingentia’s fossil said the species would have grown cyclically, enjoying rapid growth spurts for periods of time and then stopping for similar stretches, similar to trees.
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Scientists also found cavities in the bones of the species, which they believe would have lightened its weight to allow it to grow more easily.
The Ingentia also had highly developed air sacs, similar to birds, which helped keep the large animals cool and provide a large supply of oxygen.
"This finding gives a new look at the magnitude of the evolutionary explosion that the dinosaurs had," said Diego Pol, a paleontologist at the Egidio Feruglio Museum in Argentina.
“This evolutionary explosion was so great that it explains the success the dinosaurs had during the rest of their era.”