The world's oldest dinosaur—or at least the oldest dinosaur relative—was discovered in the 1930s. But it wasn't described until Wednesday, and is 10 million years older than the oldest dinosaur bones ever found.
The Nyasasaurus was likely a little larger than a dog, with a long tail, living 240 million years ago in southern Pangaea (present day Tanzania), the supercontinent that split to form Earth's current continents. Scientists had previously thought the first dinosaurs lived about 230 million years ago, according to Sterling Nesbitt, the Univeristy of Washington paleontologist who described the animal.
"It looks like it's a dinosaur or the closest relative to the dinosaur. The oldest known dinosaurs were 230 million years old, so it either pulls back dinosaurs 10 million years, or it pulls back their relatives 10 million years," Nesbitt says. The team can't say for certain whether it's a dinosaur or a close relative because they only have a few bones, including the backbone and upper arm bone. Without a skull, they have no way of knowing if it was a plant- or meat-eater.
Nesbitt says his team has been exploring the same rock bed where the Nyasasaurus was discovered since 2007 in hopes of finding a more complete fossil that would allow the team to better understand its behavior.
The Nyasasaurus bones Nesbitt's team has been studying aren't a recent discovery. The fossil was discovered in the 1930s but had stumped scientists for years. Nesbitt says one of his co-authors studied the fossil for more than 50 years before dying in the late 1990s. His team was just recently able to determine that it's a new species.
"It's definitely normal for specimens to be described years after their discovery, but this one was found exceptionally long ago," he says. "It was probably passed over because it's not a complete fossil."
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Jason Koebler is a science and technology reporter for U.S. News & World Report. You can follow him on Twitter or reach him at email@example.com.