Researchers in China have turned to a winged but flightless dinosaur to understand how early animals first learned how to fly.
In a study featured in the journal PLOS Computational Biology, scientists at Tsinghua University in Beijing examined the behavior of an early dinosaur known as the Caudipteryx to help explain how prehistoric creatures developed the ability to fly.
Despite having wings, the Caudipteryx was not able to fly during its time, some 125 million years ago. However, it was a very fast runner, known to reach speeds of about 2.5 to 5.8 meters per second.
The dinosaur's running gait generated forced vibrations that were sent throughout its body and caused its wing-like appendages to flap.
This motion is what the research believes may have served as a precursor to flight for ancient animals.
Winged Dinosaurs: Flapping Or Gliding?
Scientists have long debated whether early animals were able to flap their wings to fly, or they merely used them to glide through the air.
Previous studies have suggested that some early dinosaurs, such as the Microraptor, launched themselves into the air with the help of their wings, light bodies, and powerful hind legs.
Meanwhile, some primitive birds, such as the Archaeopteryx, were first thought to be gliders because the feathers on their wings did not seem to be strong enough for flapping.
However, recent findings have shown that the animals actually had powerful arm bones that allowed them to flap their wings in short bursts of active flight.
To help settle this argument, Jing-Shan Zhao, a mechanical engineer at Tsinghua, led his colleagues in studying the flightless Caudipteryx.
Much like modern-day emus or ostriches, the Caudipteryx had wing-like forelimbs that were too small to carry its large body during flight. This winged dinosaur may not have been able to fly but it made up for it by being an exceptional runner.
The animal's running gait and the resulting involuntarily flapping of its wings might have led to actual flight, if only it had larger and stronger appendages.
Building A Robo-Caudipteryx And Artificial Ostrich Wings
The researchers built a robotic version of the Caudipteryx. They then tested it on a treadmill to see how its body would behave while running.
They also outfitted several young ostriches, which were comparable in weight to middling Caudipteryx, with artificial wings in different sizes of feathers. They added sensors to the devices so that they could measure the various forces in play during the birds' running motion.
Zhai said the experiments helped them validate the results of earlier simulations. They showed that the Caudipteryx would have indeed flapped its wings whenever it ran.
The artificial ostrich wings, on the other hand, revealed that the longer the feathers on the devices were, the greater lift the birds would have gotten. However, the force was not enough to launch the animals into the air.
The findings suggest that the passive wing flapping practiced by the Caudipteryx may have been an early version of active wing flapping seen in modern-day animals, according to the researchers.
Despite these results, some scientists are not convinced that the dinosaur's behavior directly led to the development of flight in animals. Early species of birds, such as the Archaeopteryx, already knew how to fly some 25 million years before the first Caudipteryx existed.
Italian vertebrate paleontologist Andrea Cau pointed out that the winged dinosaur's morphology cannot be used as a 100 percent valid model when determining the ancestry of birds.
However, Cau admitted that it would be interesting to see if the model used in the Chinese study could be applied to a large sample of feathered dinosaurs as well.