This was helped by fossilized fragments of a skeleton, hidden inside a rock the size of a grapefruit overthrow one of the oldest hypotheses about the origin of modern birdsaccording to a study published this Wednesday by the Nature.

This was discovered by a research team from the British University of Cambridge and the Natuurhistorisch Museum in Maastricht one of the main features of the skull that characterizes 99% of modern birds – a mobile beak – it evolved before the mass extinction that wiped out all large dinosaurs 66 million years ago.

Their findings further suggest this the skulls of ostriches and emus they suffered an evolutionary setback, reverting to a more primitive condition after the rise of modern birds.

The study notes that using CT scanning techniques, the research team identified palate bones of a new species of large birdthey called Janavis Finalidenswho lived at the end of the dinosaur era and who it was one of the last birds with teeth.

For more than a century it has been assumed that the mechanism that allows a mobile beak it evolved after the extinction of the dinosaurs although the new finding suggests that our understanding of a modern bird skull needs to be re-evaluated.

The study finds that each of the 11,000 bird species on Earth is classified into two groups, based on available to the palate bones.

paleognaths and neognaths

According to this, ostriches, emus and their relatives would be grouped into the group of paleognathsin which, like humans, the palate bones are fused into a solid mass.

The other birds are classified in babiesthe “new jaw” group, whereby its palate bones connect with a movable joint.

These two groups were first classified by British biologist Thomas Huxley, a proponent of Charles Darwin’s evolutionary theory, whose assumption was that the “ancient” jaw configuration was the original condition of modern birds.

“This assumption has since been taken for granted,” said Daniel Field of Cambridge’s Department of Earth Sciences.

“The main reason this hypothesis has persisted is that we have not had well-preserved fossils of palatebirds from the period in which modern birds originated,” he added.

The fossil, Janavis, it was found in a quartz quarry near the border between Belgium and the Netherlands in the 1990s and was first analyzed in 2002.

Because the fossil was embedded in rock, the scientists could only base their descriptions on what they could see from the outside, and described the pieces of bone sticking out of the rocks as fragments of the skull and shoulder bones.

Nearly 20 years later, the fossil was loaned to the Cambridge research team, and Juan Benito, then a student, began to see it differently.

Realizing that the bone was a skull bone and not a shoulder bone led the researchers to conclude the condition “modern jaw”that turkeys have, it evolved before the “ancient jaw” condition of ostriches.

“Using geometric analyses, we were able to show that the shape of the palate bone fossil was extremely similar to that of live chickens and ducks,” said Pei-Chen Kuo, co-author of the study.

Field noted that “Evolution doesn’t happen in straight lines. This fossil shows that the mobile beak, a condition we’ve always thought was later in the origin of modern birds, evolved before there were modern birds.”

EFE extension