Ever since paleontologists dug up the first Archaeopteryx fossil in 1861, the strange, feathered dinosaur has been exhibit A in the case for evolution—and helped reveal that birds are actually dinosaurs. But for decades, a fierce debate has raged among scientists: Could the winged dinosaur take flight on its own? Or was it merely a lazy glider that had to jump from trees to go airborne? Now, a new analysis of dozens of bones from modern birds and flying dinosaurs may have the answer.
To find out what kind of flier Archaeopteryx was, scientists first needed to determine whether the raven-size dino could even fly. With its birdlike wings, the dinosaur looks like a shoo-in capable of flight, but its skeleton lacks features—such as a bony, keeled sternum—that modern birds need to fly. So, Dennis Voeten, a doctoral student in paleontology at the European Synchrotron Radiation Facility in Grenoble, France, and colleagues used a powerful x-ray machine called a synchrotron to examine the arm bones of three of the 11 known Archaeopteryx fossils. Unlike conventional methods, the synchrotron can detect miniscule differences in fossilized bone density even in the outermost layers—essential in figuring out whether flight was possible.
The researchers then compared their measurements to those of arm bones taken from 69 other species of flying dinosaurs and modern birds. They found Archaeopteryx’s bone density was so thin that it certainly could have gone airborne. But, how?
Modern birds have several flying styles: They can soar on thermals like hawks and albatrosses, glide and flap like storks, or explode from the ground like pheasants and roadrunners, flapping their wings to become airborne for a few hundred meters before landing. The clues to their flying styles are also in their bones. The bones of soaring birds can withstand high torsional forces—the twisting force made when wringing out a towel. Quick flight birds can bear only low torsional forces, and gliding birds fall somewhere in the middle.
To see where the 150-million-year-old Archaeopteryx fit into the mix, Voeten and colleagues examined its bone architecture. They found that its bones could tolerate low torsional forces, and so were most similar to birds like partridges that use flapping flight to go airborne for short periods, often to evade predators. Because Archaeopteryx were already propelling themselves into the sky by the late Jurassic that means avian-powered flight emerged well before they lived 150 million years ago, the researchers report today in Nature Communications.
“[This is] the strongest evidence for active flight in Archaeopteryx that has been brought forward in the last 150 years,” Voeten says. He adds that the flight would have been a bit different from modern birds: Archaeopteryx’s shoulder joint would not have allowed it to beat its wings in the same fashion, meaning the feathered dino must have used a specialized flapping motion.
But other researchers say the evidence has been there all along. Luis Chiappe, a paleontologist at the Natural History Museum of Los Angeles County in California who was not involved in the work, says it is not a revelation, even if it does support self-powered flight. He and others have concluded that Archaeopteryx could take off from the ground using a running start and that its wings, feathers, and even brain size indicated the dinosaur flew. So, the conclusion that the feathered dinosaur was a poor flyer—but a flyer—nonetheless, is one Chiappe stands behind.
“We’re looking at these old fossils in different ways. Sometimes we learn new things. Sometimes we learn things that confirm things that we believed before,” he says. “That’s the way science works.”