The iconic fossil bird Archaeopteryx has been helping scientists understand the link between dinosaurs and modern birds since it was first discovered over 160 years ago.
Now, a newly studied specimen called the “Chicago Archaeopteryx,” displayed at the Field Museum in 2024, is revealing even more secrets about this ancient creature.
This particular fossil is the best-preserved Archaeopteryx specimen ever found, with soft tissues and fine skeletal details that were never seen before.
Archaeopteryx lived around 150 million years ago during the Jurassic Period and is considered the oldest known bird.
The Chicago specimen is the smallest Archaeopteryx ever discovered, about the size of a pigeon. It was found in limestone deposits near Solnhofen, Germany, the same place where all other Archaeopteryx fossils have been unearthed.
The fossil was privately owned for decades before arriving at the Field Museum in 2022, thanks to a group of supporters.
Jingmai O’Connor, the Field Museum’s associate curator of fossil reptiles and the lead author of the study, was thrilled to examine the fossil. “I wasn’t sure what new things we would learn, but this specimen is so well-preserved that we are discovering a lot of new information,” O’Connor said.
The fossil’s delicate bones are encased in extremely hard limestone, making it impossible to remove completely from the surrounding rock without risking damage. To solve this problem, the team used advanced tools, including a CT scanner, to create three-dimensional images of the fossil.
“A CT scanner is basically a machine that takes a series of X-rays to build a 3D image,” O’Connor explained. This allowed the team to see exactly how far they could safely chip away the rock without harming the fossil.
They also used ultraviolet (UV) light to reveal fine details in the fossil’s bones and even its soft tissues, such as the scales on the bottom of its toes. “There’s something about the chemical composition of Solnhofen fossils that makes the soft tissues glow under UV light,” O’Connor said.
This technology allowed the team to identify parts of the fossil that were invisible to the naked eye.
The discovery was made possible by a team led by Akiko Shinya, the chief fossil preparator at the Field Museum. Shinya and her team worked carefully for over a year, removing bits of rock and preserving as much detail as possible. O’Connor believes that many Archaeopteryx fossils could have shown similar features, but rough preparation techniques in the past may have destroyed crucial details.
The researchers focused their study on the head, hands, feet, and wing feathers of the Chicago Archaeopteryx.
They found that the bones in the roof of the mouth could help explain how birds evolved a special feature called cranial kinesis, which allows their beaks to move independently of their skulls. This feature might have helped birds adapt to different environments, contributing to the evolution of over 11,000 bird species alive today.
The preserved soft tissues in the hands and feet suggest that Archaeopteryx spent much of its time walking on the ground and may have even been able to climb trees. But perhaps the most exciting discovery involved its wing feathers. The Chicago specimen showed long feathers on its upper arm, called tertials, which had never been seen before in an Archaeopteryx fossil.
These feathers are important for flight. In modern birds, tertial feathers fill the gap between the wing and the body, preventing air from passing through and disrupting lift.
The fact that Archaeopteryx had these feathers suggests that it could actually fly—something that has been debated for years. O’Connor noted that feathered dinosaurs closely related to birds do not have these tertial feathers, suggesting that they couldn’t fly, while Archaeopteryx could.
This new discovery adds to growing evidence that flight may have evolved more than once among dinosaurs.
“We’re learning something exciting and new from just about every part of the body that we have preserved,” O’Connor said. She believes that this study is only the beginning of what the Chicago Archaeopteryx has to teach us about the evolution of birds and flight.
The study was conducted by a team of scientists including Jingmai O’Connor, Alex Clark, Pei-Chen Kuo, Yosef Kiat, Matteo Fabbri, Akiko Shinya, Constance Van Beek, Jing Lu, Min Wang, and Han Hu. Their work is helping to uncover new details about how birds first took to the skies, millions of years ago.
Source: Field Museum.
