The spontaneous flaps of a running dinosaur’s ‘wings’ might have paved the way for true powered flapping.

Dinosaurs whose primitive wings flapped as the animals ran could have helped to pioneer true avian flight.

The origin of bird flight has been endlessly debated since the discovery of the feathered dinosaur Archaeopteryx in 1861. To understand how winged dinosaurs first got off the ground, Jing-Shan Zhao at Tsinghua University in Beijing and his colleagues focused on Caudipteryx — a two-legged, flightless relative of modern birds that lived around 125 million years ago. The team modelled the vibrations created by a hurrying Caudipteryx’s quick steps and the resonance of those vibrations through the animals’ feathered proto-wings.

As the peacock-sized creatures gathered pace, their wings would have spontaneously moved up and down in a flapping motion, the researchers found. The team’s modelling results were confirmed by experiments with both a life-sized robotic model of Caudipteryx and with juvenile ostriches, which are comparable in size.

The passive flapping of running dinosaurs’ feathered limbs was a first step toward active flight, the authors suggest.