No one really knows when dinosaurs evolved.
Hoping to clear up this mystery, researchers have been studying the mysterious fossil of Nyasasaurus parringtoni, which predates all other dinosaurs by 10 million to 15 million years.
Their analysis appears today, Dec. 4, in the journal Biology Letters. From what they found, this ancient-of-the-ancients finding could be either the world's oldest dinosaur, or at least the closest relative to the dinosaurs ever discovered.
"If the newly named Nyasasaurus parringtoni is not the earliest dinosaur, then it is the closest relative found so far," study researcher Sterling Nesbitt, of the University of Washington, said in a press release.
"Nyasasaurus and its age have important implications regardless of whether this taxon is a dinosaur or the closest relatives of dinosaurs," Nesbitt said. "It establishes that dinosaurs likely evolved earlier than previously expected and refutes the idea that dinosaur diversity burst onto the scene in the Late Triassic, a burst of diversification unseen in any other groups at that time."
Nyasasaurus is the size of Labrador retriever with a really long tail, and was discovered in the early 1930s in the Ruhuhu Valley of Southern Tanzania, but wasn't described until now. While the oldest known dinosaurs date back to the Triassic period about 230 million years ago, Nyasasaurus dates back to 243 million years ago, based on the stratified Earth in which it was found.
Before the analysis of the Nyasasaurus fossils, the closest relatives to the early dinosaurs were considered to be the silesaurids, a sister-lineage of animals that evolved around the same time as the dinosaurs, but took another evolutionary path. The two lineages have a common ancestor sometime in the early Middle Triassic.
Based on an analysis and comparison of the Nyasasaurus bones with those of early dinosaurs and silesaurids, the researchers were able to say that Nyasasaurus is either oldest example of the dinosaur lineage, or the closest relative to dinosaurs in the sister-linage of the silesaurids ever found.
The findings suggest that dinosaurs evolved at the latest during the middle Triassic Period, and supports the hypothesis that dinosaurs came from the southern portion of Pangaea, which is now South America, Africa, Madagascar, Antarctica, Australia, and India.