Dating back more than 65m years, specimen’s mobile palate challenges understanding of avian evolution.

Non-avian dinosaurs, including tyrannosaurs, also had a fused palate, as do a small number of modern birds such as ostriches and and cassowaries.

“The assumption has always been … that the ancestral condition for all modern birds was this fused-up condition typified by ostriches and their relatives just because it seems simpler and more reminiscent of non-bird reptiles,” Field added.

The study, which was published in the journal Nature, is expected to ruffle feathers, not only for suggesting the mobile palate predates the origin of modern birds but that the immediate ancestors of ostriches and their relatives went on to evolve a fused palate.

Prof Mike Benton, a palaeontologist at the University of Bristol who was not part of the research, said the study raised questions of the position on the bird family tree of three unusual, extinct groups that lived after the mass extinction including Dromornithidae, known as demon ducks, and Gastornithidae, thought to be a type of giant flightless fowl