An Argentinian farm worker has stumbled across a set of dinosaur bones that appear to come from a previously undiscovered species which is the largest land-based creature ever.

Experts at Argentina’s Museum of Palaeontology Egidio Feruglio believe the bones are from a previously unchartered member of the Titanosaur family, a type of sauropod. That’s the long necked, long tailed form that might be described as the classic dinosaur shape.

Altogether, the remains discovered in a Patagonian desert consist of around 150 bones from seven different creatures. The size estimate is based largely on a complete thigh bone.

From that, the palaeontologists believe the currently unnamed species would have been around 40 meters long, 20 meters tall and weigh 77,000 kilograms. Among the numerous comparisons that have been made are that it would have been just longer (and considerably heavier) than a Boeing 737 and be the height of a seven story building.

Until now, it was thought the largest dinosaur crown belonged to a fellow sauropod discovered in the same region and known as Argentinosaurus, which is thought to have weighed around 70,000 kilograms.

It’s hard to be certain however, as different fossil collections give different levels of evidence with which to work. The new finding included more bones than that were with Argentinosaurus, so the size estimate is likely more accurate. Of course, it’s always possible Argentinosaurus was an underestimate.

In both cases, the estimates also rely on paleontologists trying to figure out the proportions of the dinosaur to extrapolate size from individual bones, something that’s difficult without a complete skeleton.

Although it’s likely the new species has the largest dimensions of any creature in Earth’s history, it’s weight is only a little over half of that of a blue whale.

(Image credit: Museum of Palaeontology Egidio Feruglio)