A dinosaur that walked the Earth 100 million years ago but wasn’t discovered until 2012 was actually the largest to ever exist, according to a new study. The plant-eating behemoth averaged 122 feet long and weighed 76 tons.

The long-necked dinosaur was discovered by a shepherd in the Argentinian desert province of Chubut in 2012, after he noticed the tip of a large fossil bone sticking out of a rock.

But the finding turned out to be more than just a big bone. In fact, it was an enormous discovery – on more than one level.

Scientists soon realized that a new species of dinosaur had been unearthed, and it was so big that its femur alone measured 7.8 feet (2.37 meters) in length.

The dinosaur – which scientists say was the biggest of a group of large dinosaur called titanosaurs – has now been officially named ‘Patagotitan mayorum’ after the Patagonia region where it was found and the Greek word ‘titan,’ which means ‘large.’

“There was one small part of the family that went crazy on size,” said Diego Pol of the Egidio Feruglio paleontology museum in Argentina, a co-author of a study which analyzed six fossils of the species, as quoted by AP.

The P. mayorum has now been given the award of largest dinosaur ever to walk the Earth, averaging a length of 122 feet (37 meters) and height of 20 feet (six meters) at the shoulders. It weighed around 76 tons (69 metric tons).

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In short, the dinosaur was as heavy as a space shuttle or a Boeing 737.

Those numbers make the Tyrannosaurus Rex and other meat-eaters “look like dwarfs when you put them against one of these giant titanosaurs,” Pol said.

But despite their intimidating size, Pol believes the vegetarian P. mayorum was a gentle giant.

“I don’t think they were scary at all,” he said. “They were probably massive big slow-moving animals.”

“Getting up. Walking around. Trying to run. It’s really challenging for large animals,” he added.

Researchers aren’t quite clear on how the species became so big, but study co-author José Luis Carballido, from the Museum of Palaeontology Egidio Feruglio in Argentina, believes part of it had to do with available food.

“We do not know yet why we have such drastic change in body mass at this time here in Patagonia. There are some major events that are occurring at this time relating to weather and plant availability. Titanosaurs were herbivores, so certainly they had the food they needed, and plants are directly constrained by the weather. Probably the weather helped [cultivate] a particular group of plants living in Patagonia,” Carballido told Newsweek, adding that giant titanosaurs are thought to have only lived in Patagonia.

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He went on to state that the P. mayorum, like other herbivores, likely grew to be very large so it could better avoid being attacked by predators.

“The bigger it was, the less predators will try to attack it,” he said.

A cast of the dinosaur’s skeleton is on display at the American Museum of National History in New York. However, it’s so big that its head sticks out into a hallway.

Despite its impressive size, Carballido believes an even larger dinosaur could have walked the Earth, but it probably wasn’t much bigger than the P. mayorum.

“There could be [bigger], but probably we are pretty close to the size limit,” he said.

Prior to the discovery of the P. mayorum, scientists believed the title of world’s biggest dinosaur belonged to the Argentinosaurus, another titanosaur.

The study conducted by Pol and Carballido was published in the journal Proceedings of the Royal Society B: Biological Sciences on Tuesday.