Dinosaurs | Wings to run faster

Dinosaurs first used their wings to run faster. This is the theory of a Montreal study on the ancestors of birds.

Telltale footprints

A 106 million-year-old fossil track discovered in South Korea shows the gait of one of the ancestors of modern birds. The first prints are close together, meaning he was walking slowly, at around two kilometers per hour.

But further on, the space between the paw prints lengthens to 30 centimeters. Since this little dinosaur measured only 5 cm at the waist, this means that it ran at 40 km/h.

According to the lead author of the study, Hans Larsson, of McGill University, this dinosaur could never have reached this speed using only its muscles.

“The muscles weren’t strong enough either. It had to have another mode of propulsion than its two legs. »

This is the first evidence that feathered dinosaurs used their wings to run faster.

The study was published in the academic journal PNAS.

Cousin of the velociraptor

How does Mr. Larsson know that it is a dinosaur and not a bird – the first having appeared 150 million years ago? “These are two-toed prints, and throughout the Cretaceous [il y a 145 à 66 millions d’années]the birds had three or four toes,” replies Mr. Larsson.

He also knows that it is a Dromaeosauriformes are rarea “microraptor” cousin of the velociraptor from the Jurassic Park films, because no other group of dinosaurs had two fingers. It is one of the smallest known dinosaurs.

Dried mud in South Korea

The footprints were discovered on a preserved plaque of dried mud found near Jijun, South Korea. “We see everything, even the traces of water drops and insects,” emphasizes Mr. Larsson.

The absence of other prints excludes the possibility that the animal used its front legs to go faster.

Mr. Larsson is a specialist in the evolution of skeletons, joints and muscles. “Alex [Dececchi, coauteur de l’étude venant de l’Université d’État du Dakota] told me about these prints when they were described in Scientific Reports in 2018. He told me there must be a mistake. »

A biplane on four legs

Dromaeosauriformes are rare had wings on its four legs. “Since it couldn’t move its wings as much as today’s birds, it made it look like a biplane. »

This microraptor could have jumped 100 to 200 meters. “A researcher in the 1990s suggested this possibility. We confirmed that it was possible with skeletal models, but this is the first fossil evidence. »

The next step will be to reconstruct a digital model of the microraptor skeleton to simulate walking, running and jumping.

Developments

This discovery shows that there have been several evolutions of animal flight. “Originally, we had the idea that dinosaurs climbed into trees and started gliding,” says Larsson. There is more diversity than we thought. »

Gliding arboreal dinosaurs existed, but they were very rare. “And they are not the ancestors of birds, like microraptors. »

As this microraptor appeared before birds, 164 million years ago, it could be the one that “invented” flight.

Flying reptiles, such as the pterodactyl, appeared later, 150 million years ago.