Scientists generally agree that today’s birds descend from ancient flying dinosaurs, but nobody is sure exactly how the first flying dinosaurs actually took flight. A group of researchers from Tsinghua University and the Chinese Academy of Sciences think they might be able to piece together the origins of flight using a mix of fossils, mathematical models, robotic models, and modern ostriches.

The scientists started their research with the dinosaur called Caudipteryx. From this dinosaur’s fossils, researchers knew that the creature walked on land and had feathers on its upper appendages, or wings. To understand how the animal moved, they estimated its weight and how fast it moved. Using the length of the dinosaur’s legs, they decided that it likely weighed about 11 pounds and ran up to about 18 miles per hour. From these estimates, the researchers used a mathematical model that assumed the dinosaur’s limbs worked like springs, where jolts in the legs exerted forces on the wings. This model indicated that at several speeds, the dinosaur’s wings would flap as a natural response to the forces of running, much like how swinging our arms when running feels natural.

To test the results of the model, the scientists built a robot the mimicked the shape of Caudipteryx. They put force sensors on the wings of the robots to determine whether they were experiencing lift as the robot ran. As the wings pushed down on the air, the air pushed back up on the wings. Eventually this lift force would allow birds to use the flapping motion to leave the ground and take flight. When they set the robot running at the speed the mathematical model suggested would result in flapping, they saw the wings start to flap. To confirm the results of the robot in a living organism, the scientists outfitted a juvenile ostrich with a backpack containing Caudipteryx-like wings and force sensors and observed the bird as it ran with the backpack. The ostrich was chosen because it is about the same size and shape as ancient Caudipteryx. Observations revealed that the wings also flapped as the ostrich ran.

From their data, the researchers concluded that flight in the descendants of Caudipteryx could have evolved directly without an intermediate stage where the animals glided through the air without actively controlling their flight be flapping their wings. Future work will focus on elucidating which animals participated in the transition from flightless dinosaur to early flighted birds and what the different steps in that transition looked like.

Managing Correspondent: Emily Kerr

Popular Press Article: Robo-dino helps to pinpoint the origins of dinosaur flight

Scientific Article: Identification of avian flapping motion from non-volant winged dinosaurs based on modal effective mass analysis

Image Credit: Caudipteryx zhoui fossil and model, Ghedoghedo, Wikicommons