Bird feathers unlock mystery of which dinosaurs could fly

By Imogen Howse via SWNS

Analysis of birds’ feathers could reveal which dinosaurs were capable of flight, a new study has found.

Scientists have for a long time struggled to understand the differences between the wings and feathers of birds that can’t fly, such as penguins and ostriches, and those of birds that can.

This has made it difficult to establish which dinosaurs could fly, as all birds evolved from dinosaurs that survived when an asteroid hit Earth 66 million years ago.

Birds are therefore the closest things academics have to prehistoric creatures – making them the gateway to better understanding them.

Researchers previously discovered which dinosaurs had feathers via the study of modern birds, but this doesn’t prove which dinosaurs could fly.

In fact, a group of dinosaurs called Penneraptorans developed feathers long before they were capable of flight, likely for the purpose of insulation or to attract a mate.

But a team from the Field Museum in Chicago in the United States has now discovered a group of characteristics that all flying birds have in common – offering an insight into which dinosaurs could fly.

Paleontologist Professor Jingmai O’Connor and Dr. Yosef Kiat, a researcher at the Field, examined hundreds of fossilized birds in various museum collections.

They studied the size and shape of wing bones, the symmetry or asymmetry in preserved feathers, and the number of different types of wing feathers.

They then compared these to 346 different species of living birds, such as hummingbirds, hawks, pelicans, and penguins.

O’Connor explained: “Through our collaboration, we were able track modern birds’ traits in fossils that are 160-120 million years old, and therefore study the early evolutionary history of feathers."

The pair found that the long primary feathers along the tips of wings are asymmetrical in birds that can fly, and symmetrical in birds that can’t.

Similarly, they discovered that in flightless birds, the number of feathers varies widely – but in flighted birds, they only range between nine and 11.

“Penguins have more than 40, while emus have none,” said O’Connor. “It’s a deceptively simple rule that’s seemingly gone unnoticed by scientists.”

Dr. Kiat added: “It's really surprising, that with so many styles of flight we can find in modern birds, they all share this trait of having between nine and 11 primary feathers.

“I was surprised that no one seems to have found this before.”

In addition to modern birds, the two scientists also examined 65 fossil specimens from 35 different species of extinct birds to confirm their findings.

For example, they studied the feathered dinosaur Caudipeteryx. These had nine primary feathers, but those feathers were symmetrical – with the wing proportions making flight impossible.

“It’s possible that Caudipteryx had an ancestor that was capable of flight, but that trait was lost by the time Caudipteryx arrived on the scene.

“Since it takes a long time for the number of primary feathers to change, the flightless Caudipteryx retained its nine primary feathers,” O’Connor said.

Velociraptors are another example of a dinosaur that had feathers – but were not capable of flight.

Meanwhile, other feathered fossils’ wings seemed flight-ready – including those of the earliest known bird, Archaeopteryx, and Microraptor, a tiny, four-winged dinosaur that isn’t a direct ancestor of modern birds.

O’Connor and Dr. Kiat argue that their study, which has been published in the journal PNAS, could transform the way scientists study the origins of dinosaur flight.

“Our study, which combines paleontological data based on fossils of extinct species with information from birds that live today, provides interesting insights into feathers and plumage—one of the most interesting evolutionary novelties among vertebrates.

“We have found that you can basically look at the overlap between the number of primary feathers and the shape of those feathers to determine if a fossil bird could fly, and whether its ancestors could.

“This helps us learn about the evolution of these dinosaurs, and highlights the importance of integrating knowledge from different sources for an improved understanding of evolutionary processes," Dr. Kiat said.

O’Connor added: “Dinosaurs, including birds, are one of the most successful vertebrate lineages on our planet.

“One of the reasons that they're so successful is their flight, and another reason is probably their feathers, because there's such versatile structures.

“So any information that can help us understand how these two important features co-evolved that led to this enormous success is really important.”