Reposted from the Natural History Museum of Utah’s Science Stories.

Birds are the most diverse group of land animals on Earth. They’re also dinosaurs—the only ones that survived the mass extinction event 66 million years ago. To understand how birds evolved from their reptilian ancestors, and possibly uncover the secret to their survival, paleontologist Jingmai O’Connor, Ph.D., studies the oldest known bird: Archaeopteryx.

“Archaeopteryx is often seen as a missing link,” O’Connor said. “It was the first fossil evidence of evolution by means of natural selection…and so it’s considered the icon of evolution.” She works at the Field Museum of Natural History in Chicago as the associate curator of fossil reptiles, where she researches ancient birds and avian evolution.

Only 14 Archaeopteryx fossils have been discovered. Most are housed in Germany, where they were recovered. But a few have made their way to other collections. One of the best specimens ever found is now at the Field Museum. Known colloquially as the Chicago Archaeopteryx, it’s the best example of this fossil bird to date. As a keynote speaker for the Natural History Museum of Utah’s DinoFest this year, O’Connor will present a talk about the Chicago Archaeopteryx at 12 p.m. on Sunday, Feb. 1. Visitors can experience the rest of the DinoFest: Prehistoric Skies event Jan. 31 through Feb. 1.

From fierce dinosaurs to feathered flyers

It might come as a surprise that pigeons roosting in a subway station or tiny hummingbirds visiting a garden are dinosaur descendants. But it’s true: the group that Tyrannosaurus rex belonged to, theropods, was the humble origin of modern-day birds (but birds evolved from much smaller species, more like Velociraptor). Archaeopteryx is vital to researchers’ understanding of how that evolution happened, because it clearly has both dinosaur and bird traits.
“It’s recording this transition from a typical reptile to a bird reptile—linking theropod dinosaurs with the bird dinosaurs.”

For example, Archaeopteryx had feathers, hollow bones and wings. It was roughly the size of a raven and had a wishbone, or furcula, a hallmark feature of birds today. But it also had a mouth full of sharp teeth and a long, bony tail. So, although it shares features with modern birds, “Archaeopteryx looked very different,” O’Connor said. It lived around 150 million years ago in the Jurassic period. While other dinosaurs had also evolved feathered wings before then, Archaeopteryx is the first known example of an animal that likely used those adaptations to fly.

Representing the transition between birds and dinosaurs, Archaeopteryx fossils help researchers understand how feathered friends on Earth today emerged. The Chicago Archaeopteryx is a landmark specimen and pivotal to that goal because its features are more complete. Not only is most of the entire skeleton present, but O’Connor could see detailed remains of soft tissue, particularly when viewing the fossil under ultraviolet light. It is also more three-dimensional than most other specimens, which tend to get squished by geological forces.

Ancient birds teach us about modern at-risk species

All Archaeopteryx fossils found thus far hail from southern Germany. They’ve been unearthed from the Solnhofen Limestone formation, a band of limestone that formed from mud when the area was largely covered in a shallow sea and a smattering of islands. The first Archaeopteryx fossil—a feather—was discovered in the area in 1861. Around 130 years later, quarry workers unearthed the Chicago Archaeopteryx. It was in private ownership until the Field Museum acquired it in 2022.

“The fossil was unprepared—meaning it was still mostly encased in rock—making the innards of the acquisition a mystery,” O’Connor said. She could tell that the feathered wings were there, but that was it. But after X-raying the fossil, O’Connor and her team knew it was something special.

“I remember telling the president of the Field Museum…it’s not going to be the best Archaeopteryx, but it’s not going to be the worst Archaeopteryx,” she recalled. “It actually turns out to be the best Archaeopteryx of them all.”
Missing only one claw on its left hand, the bird was preserved with its wings outstretched, revealing an unprecedented view of its anatomy.

It took scientists nearly a year to prepare the fossil. In that time, O’Connor prepared two exhibits and wrote a research paper on the specimen, painstaking work that represents how stressful the pressures of paleontology can be. Although she didn’t originally set out to study fossils specifically, O’Connor knew from a young age she wanted to pursue geology like her mom. After taking a class on historical geology, she realized paleontology was the right path.
“I really fell in love with evolution and how complex and fascinating it is. And if you are a geologist, then the way to study evolution is through the lens of paleontology.”

At the time that O’Connor chose a subject for her Ph.D., researchers were frequently publishing novel insights about ancient birds and their evolution. She felt that birds held the most promise for making an impact and turned her focus there. Her work on Archaeopteryx shows that she chose right—but her mark on the bird world goes far beyond that. This fall, O’Connor helped name 50 Mesozoic birds, a milestone thus far in her career. The 50th, Chromeornis funkyi, is named after one of her favorite techno-funk bands, Chromeo. Chromeornis was a small, sparrow-sized bird with some unique features—such as a long snout with teeth at the end—that hinted to O’Connor it could be a new species. The animal seems to have died from trying to regurgitate a large mass of rocks.

Chromeornis, Archaeopteryx and O’Connor’s other work on birds are helping piece together why they are the only dinosaurs to have survived the Cretaceous extinction event.

“The only way that we can actually understand what organisms are most vulnerable during this current environmental crisis is by seeing how different organisms have responded to environmental crises in the past,” she said. “The fact that we are in a mass extinction has made paleontology all of a sudden incredibly relevant.”

Come to DinoFest Prehistoric Skies for a journey into the past that you can’t find anywhere else. Enjoy special access to the Paleo Preparation Lab and Paleontology Collections to get up close to incredible fossils. This year, for the first time, the museum is offering paleontology-themed workshops for fans seeking more opportunities to explore DinoFest.

Header photo: Chicago Archaeopteryx fossil. Credit: Wikicommons