Alamosaurus crowned the largest dinosaur in North America

Paleontologists have known about the Alamosaurus for years, and they believed they had a fairly accurate estimate of its size and weight, but it turns out they were wrong.

Denver Fowler, a researcher at Montana State University, and State Museum of Pennsylvania’s Robert Sullivan came to the conclusion that the Alamosaurus was significantly more massive than originally thought after examining fossils they collected in New Mexico between 2003 and 2006.

Fowler estimates that the Alamosaurus could have been 80 feet tall and weighing in at roughly 70 tons, give or take a few pounds. The fossils the two examined were two vertebrae and a leg bone from the long-necked herbivore.

Fowler and Sullivan originally thought that the two vertebrae recovered were whole pieces of vertebrae, not fragments. “We dug around it and surrounded it in plaster, then we flipped it over to get it out of the ground- that was the point at which we could see what we actually had was not all that much,” Fowler said.

Assuming Fowler and Sullivan are correct in their estimates, the Alamosaurus would be around the same size as the massive South American Argentinosaurus, which also weighed 70 tons.

“Over the past 20 years, Argentinean and Brazilian paleontologists have been unearthing bigger and bigger dinosaurs, putting the rest of the world in the shade,” Fowler said. “However, our new finds not only show that Alamosaurus is newly recognized as the biggest dinosaur from North America, but also that it was right up there with the biggest South American species: The U.S. is back in the fight for the No.1 spot.”


[Image credit: Artist’s conception of the Alamosaurus sanjuanensis by Mariana Ruiz Villareal]