For the past 130 years or so, the taxonomy of dinosaurs has been more or less firmly divided into two orders, Ornithischia and Saurischia, each of which has two suborders within it. However, this conventional understanding has now been challenged by a study that suggests the classification, and even the names, of the orders is wrong, and proposes that dinosaurs originated in the Northern Hemisphere, and not in the Southern Hemisphere, as is popularly believed.

In a paper titled “A new hypothesis of dinosaur relationships and early dinosaur evolution,” published Wednesday in the journal Nature, scientists from the University of Cambridge and Natural History Museum in London propose moving the suborder Therapoda out of Saurischia and combining it with Ornithischia, to create a new grouping called Ornithoscelida.

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Matthew Baron of the University of Cambridge and lead author of the study, said in a statement Wednesday: “When we started our analysis, we puzzled as to why some ancient ornithischians appeared anatomically similar to theropods. Our fresh study suggested that these two groups were indeed part of the same clade. This conclusion came as quite a shock since it ran counter to everything we’d learned.”

David Norman, also from the university and co-author of the study, added in the statement: “The repercussions of this research are both surprising and profound. The bird-hipped dinosaurs, so often considered paradoxically named because they appeared to have nothing to do with bird origins, are now firmly attached to the ancestry of living birds.”

Analysis of the family tree of dinosaurs led the scientists to another conclusion they weren’t expecting, one regarding the place of origin of the animals. The oldest dinosaur fossils, from about 243 million years ago, have been found in modern-day South America, which was a supercontinent called Gondwana at the time when dinosaurs first showed up, leading to the belief that dinosaurs originated there. But examination by researchers showed dinosaurs could have evolved on Laurasia, the other supercontinent of the time, both of which were quite close to each other.

Paul Barrett of the Natural History Museum, another co-author of the study, said in the statement: “This study radically redraws the dinosaur family tree, providing a new framework for unraveling the evolution of their key features, biology and distribution through time. If we're correct, it explains away many prior inconsistencies in our knowledge of dinosaur anatomy and relationships and it also highlights several new questions relating to the pace and geographical setting of dinosaur origins.”