A group of paleontologists has found that dinosaurs evolved much more rapidly than previously thought. They used a new dating technique to accurately determine the age of the dinosauromorphs, the early dinosaur relatives. Scientists were surprised to find that dinosaurs might have emerged just 4 million years after dinosauromorphs. Previous estimates suggested that the giants evolved 9 million to 14 million years after their early relatives.
Charanes Formation is a treasure trove
Findings of the study were published in the Proceedings of the National Academy of Sciences. Researchers led by University of Buenos Aires paleontologist Claudia Marsicano concluded that the early dinosaur fossils found in the Chanares Formation in Argentina were previously misdated. The Argentinian Chanares Formation contains fossils of both dinosaurs and dinosauromorphs, making it earlier for researchers to track their evolutionary timeline.
The two co-existed for millions of years before true dinosaurs would out-compete their smaller predecessors. The Chanares Formation has hundreds of meters of sediments. It dramatically reduces the margin of error because researchers can study the complete history in this one basin. And it has layers that are mixed with volcanic ash that can be dated, said Dr Randall Irmis, the co-author of the study.
Dinosaurs appeared in fossil records 231 million years ago
Scientists took rock samples holding the fossils and extracted zircon crystals from the volcanic ash, which contain lead and uranium. Over time, uranium decays into lead at a known rate. Paleontologists measured the ratio of uranium to lead in these crystals to date them accurately.
They found that the Chanares fossil layer was 5-10 million years younger than previously thought, meaning dinosauromorphs came 5-10 million years later than the previous evolutionary timeline. Past studies estimated that dinosauromorphs were 240-245 million years old. But the new study showed that they were 235 million years old, said Dr. Irmis.
It places these dinosauromorphs pretty close to when true dinosaurs appeared in the fossil record approximately 231 million years ago. The new technique has not yet been applied to other fossil formations in other parts of the world.