The latest fossil, named Chicago Archeopteryx, is the 14th known specimen of this remarkable Jurassic species.

Chicago Archeopteryx. Image credit: Delaney Drummond/Field Museum.

The Archeopteryx inhabited the Jurassic period around 150 million years ago.

The Chicago specimen is the smallest known, roughly the size of a pigeon. Its fragile hollow bones are embedded in exceptionally hard limestone.

As with other Archeopteryx fossils, this new find was located in limestone deposits near Solnhofen, Germany.

This particular fossil was uncovered by a private collector before 1990 and has remained privately held since then.

A coalition of supporters assisted the Field Museum in acquiring it, and it arrived there in August 2022.

“When we initially obtained the specimen of Archeopteryx,” remarked Dr. Jinmaio Connor, the Field Museum’s Associate Curator of Fossil Reptiles.

“Despite the fact that Archeopteryx has been known for over 160 years, we were uncertain about the new insights we might gain.”

“However, our specimens are exceptionally well preserved and prepared, so we are uncovering a wealth of new information, from the tip of the beak to the tip of the tail.”

Thanks to the outstanding preservation of the specimens, paleontologists conducted high-resolution CT scans and digital 3D reconstructions.

The findings reveal an almost entirely intact skull, featuring a well-preserved palate region.

“The bones in the roof of the mouth provide valuable insights into the evolution of what is known as a skull, a feature of modern birds that allows them to move their beaks independently from the braincase,” Dr. O’Connor explained.

“While it may not seem thrilling, for those studying bird evolution, it’s quite significant, as it is thought that specialized skulls may have evolved for varying ecological niches.”

“Additionally, the soft tissues preserved in Chicago Archeopteryx‘s hands and feet support the idea that Archeopteryx likely spent considerable time on the ground and may have even climbed trees.”

An illustration of Archeopteryx depicting its characteristic feathers that would have assisted flight. Image credit: Michael Rothman.

The wing feathers of the Chicago Archeopteryx raise an enduring scientific question regarding the origins of flight in dinosaurs.

“Archeopteryx is not the first dinosaur with wings, nor the first to possess ‘wings’,” Dr. O’Connor explained.

“However, it is considered the earliest known dinosaur that managed to achieve powered flight using its wings.”

“This section of the paper is particularly intriguing to me, as it provides evidence that Archeopteryx employed feathered wings for flight.”

Key to Archeopteryx‘s flight may be a set of feathers previously unrecognized in the species—a group of long upper arm feathers known as Tertials.

“In comparison to most modern birds, Archeopteryx has an exceptionally long upper arm bone,” noted Dr. O’Connor.

“If you are flying, having an elongated upper arm bone can create a gap between your long primary and secondary wings and the rest of your body.”

“If air flows through that gap, it can disturb the lift being generated, making flight impossible.”

Nevertheless, modern birds have developed solutions to this issue, employing a series of tertial feathers to bridge the gap between their bodies and wings.

“Our specimen is the first Archeopteryx to be preserved and studied for its long feather structure,” Dr. O’Connor said.

“These feathers share similarities with those of birds, yet are absent in non-avian feathered dinosaurs.”

“Their wing feathers terminate at their elbows, indicating that these non-bird dinosaurs could not fly, whereas Archeopteryx could.”

“This also supports the idea that flight in dinosaurs may have evolved multiple times, which I find very exciting.”

The team’s research findings were published in the journal Nature this week.

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J. O’Connor et al. Chicago Archeopteryx offers insights into early avian evolution. Nature Published online May 14, 2025. doi:10.1038/s41586-025-08912-4