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Scans show that Archaeopteryx’s arm bones were able to flap like a pheasant

For over 100 years, the biggest point of fascination on Archaeopteryx fossils wasn’t the animal’s bones, but its feathers. When first discovered in the 1860s, people were understandably fixated on the impressions of the specimens long feathers left in the rock around the skeleton. They appeared to be long and rigid like a modern bird’s feathers, right down to tiny, interlocking barbules that would give each feather more strength. On the other hand, Archaeopteryx’s skeleton seemed to contradict this bird-like anatomy, as its long tail and toothed mouth aren’t found in any modern avians, and its breast bone lacked the large keel that modern birds use to attach powerful chest muscles needed for flapping. To dig in a little deeper, the latest study of Archaeopteryx looked inside the animal’s bones, and found that they probably could fly like a bird, but only those birds that stay close to the ground.

X-ray scanning for signs of strength

With the exterior of Archaeopteryx’s fossil having been extensively documented, researchers opted to look at the inner structure of each bone in the European Synchrotron Radiation Facility. The powerful x-rays would let them look at delicate structures inside these 150 million-year-old fossils with amazing resolution without needing to damage them in the process. The goal was to measure the arm bones’ torsional resistance, which is how well they would stand up to being twisted when used in flight. Since modern birds that do a lot of continuous flying have higher torsional resistance than birds that don’t, this measurement could be used as another way to assess how flight-ready Archaeopteryx was, regardless of feathers or breast bones. To make sure they weren’t missing a larger pattern, the bones were also compared to crocodilians and pterosaurs as well.

To nobody’s surprise, Archaeopteryx didn’t soar like an eagle, or even a Quetzalcoatlus. However, its arms did appear to handle more than just crawling around, most closely resembling birds like quails and pheasants that are known for short bursts of flight, usually to avoid danger. The x-ray scanning also revealed a large number of blood vessels in Archaeopteryx’s skeleton, a trait associated with high growth rates and metabolism. This would indicate that while the dinosaur wasn’t a bird itself, it probably grew and moved like one.

Not a fully-fledged flyer— yet

This still doesn’t make Archaeopteryx the world’s first bird, or even a bird ancestor. Other species have been found with feathers, even predating Archaeopteryx. We also don’t believe that Archaeopteryx was part of the raptor lineage that eventually developed into modern birds, and instead was a case of convergent evolution. In this case, that convergence would be the capacity for short, evasive flight, which makes sense as avoiding predators has been found to be the most likely reason any species develops wings in the first place. The one catch is how Archaeopteryx would ever get off the ground in the first place. Until evidence of something like a breast keel made from cartilage can confirm its flapping strength, we’re still not sure how well the animal could defy gravity to get itself airborne.

Source: This Famous Dinosaur Could Fly— But Unlike Anything Alive Today by Michael Greshko, National Geographic

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