Small, ancient bird fossils shed light on how early avian critters flew over the heads of dinosaurs. Using a well-preserved wing of a 125 million-year-old ancient bird that once lived in what is now Spain, researchers found that an intricate arrangement of muscles and ligaments most likely allowed the birds to take flight, in a way that is similar to how birds fly today.

"The anatomical match between the muscle network preserved in the fossil and those that characterize the wings of living birds strongly indicates that some of the earliest birds were capable of aerodynamic prowess like many present-day birds," Dr. Luis M. Chiappe, a researcher from the Natural History Museum of Los Angeles County, said in a news release.

The complex network of muscles found in the ancient birds resembles that which controls fine wing adjustments in modern birds, allowing them to master the skies today.

"It is very surprising that despite being skeletally quite different from their modern counterparts, these primitive birds show striking similarities in their soft anatomy," Guillermo Navalón, a doctorate candidate at the University of Bristol in the U.K. and lead author of the study, said in the release.

This ability of ancient birds would have allowed them to fly over the heads of dinosaurs. However, the precise flight modes used still remain unclear, the researchers noted.

"The new fossil provides us with a unique glimpse into the anatomy of the wing of the birds that lived amongst some of the largest dinosaurs," Chiappe said in a statement. "Fossils such as this are allowing scientists to dissect the most intricate aspects of the early evolution of the flight of birds."

Their study was recently published in the journal Scientific Reports.

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