By ASHER ELBEIN NYTimes News Service
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In 1861, scientists discovered Archaeopteryx, a dinosaur with feathers, in 150-million-year-old limestones in Solnhofen, Germany. They didn’t know it at the time, but that fossilized skeleton — and the several that followed — provided a key piece of evidence for the theory of evolution, as well as for the fact that birds were actually dinosaurs.

Archaeopteryx specimens have, “maybe more than any other fossil, changed the way that we see the world,” said Jingmai O’Connor, a paleontologist at the Field Museum in Chicago.

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Over 164 years, researchers have pored over every detail of available specimens, trying to puzzle out how birds came to fly. Therefore, you might expect that such a well-studied fossil species wouldn’t be capable of surprises. But in a paper published Wednesday in the journal Nature, O’Connor and a team of researchers revealed previously unrecorded soft tissues and skeletal details from a new specimen, known as the Chicago Archaeopteryx. What they found also helps explain why some feathered dinosaurs got off the ground, if only for short-haul flights.

Sussing out Archaeopteryx’s abilities in flight and how it fit in its environment has long been tricky, O’Connor said. A majority of specimens are cartoonishly flattened by geology, making it difficult to discern important skeletal details. And while its earliest discoverers and most modern scientists have concluded that the species could likely take off, particular bodily features have left paleontologists seeking more data.

The latest specimen, acquired by the Field Museum in 2022 and on public display since 2024, allowed O’Connor’s team to begin addressing some of the anatomical uncertainties.

When the fossil arrived at the museum, it didn’t look like much. The specimen was the same color as the surrounding rock, and most of the soft-tissue remains were difficult to see, O’Connor said.

The researchers CT-scanned the fossil, building a digital map of the skeleton to help guide their preparation of the slab. They also had a secret weapon: By a quirk of chemistry, soft-tissue remains preserved in certain sediments glow under UV light, allowing the team to avoid accidentally removing feathers or skin textures while uncovering bone. That technique was not available to fossil preparators in the 1800s.

Unlike other specimens, the bones of the Chicago Archaeopteryx were preserved in three dimensions, and O’Connor’s team could better evaluate the skull’s palate. That showed the earliest signs of an evolutionary trajectory toward the skulls of modern birds, which are more mobile than those of prehistoric birds, O’Connor said.

In another lucky accident of fossilization, the carcass’s wings were separated from the body, leaving them “clearly and pristinely preserved,” O’Connor said. Upon close inspection, the team confirmed that rather than having two layers of wing feathers, as observed in earlier specimens, Archaeopteryx actually had three. In modern birds, that third layer helps link the shorter forearm to the body to create a continuous lift surface, which allows birds to sustain flight.