106-million years ago, this tiny dino-predator ran faster than any animal living today

A new study published in the journal Proceedings of the National Academy of Sciences (PNAS) reveals that Microraptors may have used their wings to enhance their speed. Led by Kyung Soo Kim of Chinju National University of Education, the international research team investigated how such a small dinosaur could have achieved impressive speeds.

Le Monde, Der Spiegel, Die Welt, and The Independent reported on the study.

In 2018, a South Korean team described the smallest known footprints attributed to a carnivorous dinosaur, likely a Microraptor, discovered near the southern town of Jinju in South Korea. The unique footprints, measuring no more than a centimeter, were fossilized imprints left by a Microraptor and were created around 106 million years ago. The trackway discovered at an excavation site in the Jinju Formation suggests that small winged dinosaurs possibly used their wings to increase their stride length.

The footprints' spacing puzzled paleontologists. Kyung Soo Kim noted that the spacing suggested the Microraptor, a biped the size of a sparrow, could have reached an impressive speed of 40 km/h (about 10.5 m/s). However, a bipedal Microraptor moving at 10.5 m/s did not seem realistic from a biophysical point of view; it would require unprecedented leg muscular force in the animal kingdom. At a certain speed, the wings would generate enough lift to overcome gravity.

The researchers considered the possibility that the Microraptor used its wings to assist its running. "We found that the author of the tracks could move at a much more reasonable speed (for example, about 6 m/s) to produce the observed track, if its run benefited from the assistance of its wings," Michael Pittman from the Chinese University of Hong Kong explained. This hypothesis suggests that the dinosaur used aerodynamic forces generated by flapping its feathered arms to achieve lift, allowing it to travel faster than if it had relied solely on the strength of its legs.

Although Microraptors are not in the lineage of dinosaurs that gave rise to modern birds, they share a common ancestry with Velociraptors and other raptors (dromaeosaurids). The tiny dinosaur with the giant name, Dromaeosauriformipes rarus, may represent an early stage in the evolution of flight among dinosaurs that are not part of the bird lineage. This behavior might have put the Microraptor on an evolutionary take-off path.

The study suggests that the origin of flight may not be a simple binary of "can or cannot" but a spectrum. "We can now move past the debate about whether pre-avian dinosaurs used their arms to help them move before flight evolved and start to uncover missing details such as which species had these abilities and when and to what extent they were developed," Pittman said.

"This is really a mosaic kind of evolution, when it comes to wings and flying. It's not a matter of, 'you don't have it' and then 'you have it'. We really have to zoom out a little further to see how some characteristics evolved in their own path, without becoming a bird," Romain Pintore at the French National Museum of Natural History in Paris commented on the findings.

"The use of wings in combination with the hind legs opened up a whole bunch of possibilities for these dinosaurs, of which we have no idea yet," Alexander Dececchi, a researcher involved in the study, stated. This assistance likely came from wings, which may have also helped make jumps to impress potential sexual partners, as seen in some modern birds.

The researchers were surprised by the estimated speed of the creature, which was about 38 kilometers per hour, approximately the speed of a modern ostrich. As Alex Dececchi stated, "The relative speed shown by our tracks is higher than any living running animal, including ostriches and cheetahs."

"I think the vast majority of feathered dinosaurs were probably doing what this guy was doing—using the wings to augment running, jumping, braking and turning," Pittman remarked.

This article was written in collaboration with generative AI company Alchemiq