U.S. paleontologists say they have discovered fossils of the largest-known dinosaur ever to roam North America, whose size rivals that of long-necked, dinosaurs from South America.
The scientists say they unearthed two enormous vertebrae and a femur, or thigh bone, of a plant-eating sauropod species called Alamosaurus. Found at a site in the southwestern U.S. state of New Mexico, the bones belonged to an adult Alamosaurus that lived 69 million years ago.
Previously, it was thought that Alamosaurus weighed 30 tons and measured about 19 meters in length. The study co-authors say their findings suggest those conclusions were based on the fossils of animals that were not fully grown when they died.
The paleontologists say the adult specimens found in New Mexico put Alamosaurus in nearly the same category as its 70-ton, nearly 40-meter-long South American cousin, Argentinosaurus. The Argentinosaurus is widely considered the biggest type of dinosaur, or any land animal, ever to have lived.
All dinosaurs became extinct 65 million years ago.
The scientists who conducted the research are with the Montana State University Museum of the Rockies, and the State Museum of Pennsylvania. The new study by researchers is published in the journal, Acta Palaeontologica Polonica.