PHILADELPHIA — It weighed as much as eight school buses.

Its neck looked like a section of oil pipeline. Its thigh bone alone was as big as a grown man.

Additional Images

This artist’s rendering provided by the Carnegie Museum of Natural History shows the Dreadnoughtus. The dinosaur had a 37-foot-long neck, 30-foot tail, and weighed an estimated 65 tons. The Associated Press

A photo, size chart and artist’s rendering of a Dreadnoughtus schrani are displayed on the laptop of paleontologist Kenneth Lacovara. Dreadnoughtus was an herbivore that ate massive quantities of plants.

Paleontologist Kenneth Lacovara works near vertebrae from a Dreadnoughtus schrani at Drexel University in Philadelphia. The immense dinosaur from Patagonia was introduced to the scientific community Thursday. The Associated Press

Say hello to Dreadnoughtus schrani.

Drexel University scientists announced Thursday they had unearthed the heaviest known dinosaur for which a weight can be accurately calculated.

In many cases, the fossils of giant dinosaurs are largely incomplete, preventing scientists from making good estimates about their size, movement and other characteristics. This one, found in southern Patagonia in Argentina, was unusually well preserved, with the scientists able to recover close to half of its 250-odd bones.

By measuring the circumference of the thigh bone and upper arm bone, the researchers calculated that this beast weighed more than 65 tons. And it was not done growing, as evidenced by shoulder bones that had yet to fuse together, said team leader Kenneth Lacovara, an associate professor of paleontology and geology at Drexel.

Lacovara named the animal after the dreadnought class of battleships from the early 20th century, so nicknamed because they feared nothing – dreaded naught. This dinosaur was so big that few predators would have dared to attack it, Lacovara said. But if one of them did, the dinosaur could have responded with a smack of its muscular, 29-foot tail.

“It essentially had a weaponized tail,” Lacovara said.

The “schrani” portion of the name is a tribute to Philadelphia tech entrepreneur Adam Schran, who helped fund the research.

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