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New dating of dino ancestor challenges Triassic timeline

Dinosauromorphs showed up too late to be Permian extinction success story

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3:00pm, December 7, 2015
illustration of  dinosauromorphs

FOSSIL BED  Early dinosaur ancestors like the pair on the right were thought to evolve around 10 million years before dinosaurs. But new dating of fossil layers in Argentina cuts that time in half, to about 5 million years.

Dinosaurs arrived hot on the tails of their more ancient relatives, reptiles called dinosauromorphs, a new study shows.   

New dating of a dinosauromorph fossil layer in a geologic formation in Argentina reveal that it’s between 5 million and 10 million years younger than previously thought. That means dinosaurs and their dinosauromorph predecessors were separated by a gap of less than 5 million years, half the time previously thought. The timescale change suggests that dinosaurs evolved relatively rapidly, and that early dinosauromorphs probably weren’t part of life’s repopulation after a major mass extinction 252 million years ago, scientists report online December 7 in the Proceedings of the National Academy of Sciences.

“It’s a very exciting result,” says Paul Olsen, a paleontologist at Columbia University not involved with the study. “It

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