“It is odd that this hypothesis has survived relatively unmolested for so long given, as you say, the radical changes that have occurred in our understanding of all other groups on Earth,” lead author Matthew Baron, a graduate student of palaentology at the University of Cambridge, told IFLScience.
“I guess because it is a simple and elegant idea,” he added. “Finally, we have shown that the old definition for dinosaur needed an update.”
The new assessment of dinosaurian evolution moves a few other subgroups around too, including placing a primitive type of meat-eating beastie within the same group as the long-necked plant-eating dinosaurs such as the Brontosaurus and Diplodocus.
“One thing that this has thrown up is the new way we have to think about the ancestral dinosaur and how it lived,” Baron noted.
The earliest dinosaurs, which emerged out of the Great Dying mass extinction event around 250 million years ago, are decidedly mysterious beings, with fossil evidence dating back to the Early Triassic being of fairly poor quality. Researchers, however, can use later dinosaur fossils to infer what their distant ancestors might have looked like.
This study is no different, and based on its newly arranged family tree, the first dinosaurs were probably small, omnivorous, walked on two legs, and had grasping hands. Scientists previously thought the first dinosaurs evolved in the Southern Hemisphere, but this study implies they first emerged in the north.
The American Museum of Natural History's Tyrannosaurus specimen. J M Luijt/Wikimedia Commons; CC BY-SA 2.5 nl
In sum, the entire evolutionary tree of the dinosaurs has been thrown into disarray.
This research currently stands alone in terms of its bold, new ideas. If, however, it’s eventually backed up by other paleontology groups, it could be, in time, considered something truly revolutionary.