- Archaeopteryx was a genus of bird-like dinosaur that lived 150 million years ago.
- Now an Archaeopteryx fossil at the Field Museum in Chicago has revealed fine details like feathers, soft tissue and skeletal features, via advanced techniques like CT scanning and UV light.
- This well-preserved specimen provides crucial evidence about the transition from dinosaurs to birds. It’s thought, for example, that this creature used its feathers to fly.
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Chicago Archaeopteryx provides fresh clues on how birds evolved from dinosaurs
Archaeopteryx – a bird-like dinosaur that lived around 150 million years ago – has played a significant role in understanding how some dinosaurs evolved to become birds. Recently, the Field Museum in Chicago added a new Archaeopteryx specimen to its collection. Scientists are calling the specimen the Chicago Archaeopteryx. Upon studying it, researchers found some soft tissue structure, fine skeletal details and even feathers in this exceptionally preserved fossil. In fact, new details about this dinosaur’s skull show that it shares some similarities with modern-day birds. Soft tissue traces also provide clues about the animal’s mobility, with its feathers suggesting it could fly.
There are 14 known Archaeopteryx fossils in all. They’ve all been found in limestone deposits near Solnhofen, Germany. But details about the Chicago Archaeopteryx discovery are largely unknown. Apparently, it was excavated by an unknown fossil hunter sometime before 1990. It apparently remained in private hands until the museum procured it in 2022.
And after meticulous fossil preparation, Field Museum unveiled the Chicago Archaeopteryx to the public in 2024.
Jingmai O’Connor is the new paper’s lead author. She said, in a statement:
When we first got our Archaeopteryx, I was like, this is very, very, very cool, and I was beyond excited. But at the same time, Archaeopteryx has been known for over 160 years, so I wasn’t sure what new things we would be able to learn. But our specimen is so well-preserved and so well-prepared that we’re actually learning a ton of new information, from the tip of its snout to the tip of its tail.
The researchers published their findings in the journal Nature on May 14, 2025.
Uncovering hidden features in the fossil
Scientists put in painstaking efforts to prepare the Chicago Archaeopteryx for further study. For instance, they very carefully preserved bone and soft tissue that were similar in color to the surrounding rock. O’Connor explained:
A CT scanner is essentially a machine that takes a series of X-rays, which it uses to build a 3-dimensional image, based on differences in density. It lets you see inside things. CT scanning was very important for our preparation process. It let us know things like, the bone is exactly 3.2 millimeters [0.12 inches] below the surface of the rock, which let us know exactly how far we could go before we would hit the bone. This is the first time a complete Archaeopteryx has been CT scanned and the data made available.
They also used ultraviolet light (UV) to illuminate the fossilized skeleton and soft tissue, and even scales at the bottom of the toes. O’Connor commented:
Previous studies have shown that there’s something in the chemical composition of Solnhofen fossils that makes the soft tissues fluoresce, or glow under UV light. So our amazing prep team utilized UV light periodically through the preparation process to make sure that they weren’t accidentally removing any soft tissues that you can’t see with the unaided eye.
We’re lucky in that this specimen happens to be extremely well-preserved, but we can also see features that probably were preserved in other specimens, but which didn’t make it through cruder preparation processes in the past. Having the preparation of this specimen done by scientists whose goal was to preserve as much tissue and bone as possible made a huge difference.
Studying this well-preserved Archaeopteryx has only just begun
The Chicago Archaeopteryx is the smallest Archaeopteryx found to date, about the size of a pigeon. And scientists have only just started their thorough analysis of it. O’Connor and her team decided to concentrate on its head, hands and feet, and wing feathers. She said:
We’re learning something exciting and new from just about every part of the body that we have preserved. And this paper is really just the tip of the iceberg.
The scientists found intriguing evidence that bones at the roof of the mouth had intermediate features between birdlike dinosaurs known as troodontids and more evolved birds of the Cretaceous Period (143 to 66 million years ago). O’Connor explained the significance of those bones:
The bones in the roof of the mouth help us learn about the evolution of something called cranial kinesis, a feature in modern birds that lets the beak move independently from the braincase. That might not sound exciting, but to people who study bird evolution, it’s really important because it’s been hypothesized that being able to evolve specialized skulls for different ecological niches might have helped birds evolve into more than 11,000 species today.
Fossilized soft tissue in the hands and feet of this Archaeopteryx also revealed clues to its mobility. In particular, they found toe pads similar to birds that forage on the ground. So the scientists suggest that it likely walked on the ground and might have been able to climb trees. In addition, the complete spine of this specimen indicated that Archaeopteryx had a longer tail than previously thought.
Could Archaeopteryx fly?
There’s been a lot of debate about some dinosaurs and their ability to fly. O’Conner observed:
Archaeopteryx isn’t the first dinosaur to have feathers, or the first dinosaur to have ‘wings.’ But we think it’s the earliest known dinosaur that was able to use its feathers to fly. This is actually my favorite part of the paper, the part that provides evidence that Archaeopteryx was using its feathered wings for flying.
The Chicago Archaeopteryx provided a valuable clue: a long set of tertial feathers. These are feathers on the upper arm. They’re closest to the body, covering the gap between the body and wing. This provides more lift for a bird to remain airborne. O’Connor explained:
Compared to most living birds, Archaeopteryx has a very long upper arm bone. And if you’re trying to fly, having a long upper arm bone can create a gap between the long primary and secondary feathers of the wing and the rest of your body. If air passes through that gap, that disrupts the lift you’re generating, and you can’t fly.
Our specimen is the first Archaeopteryx that was preserved and prepared in such a way that we can see its long tertial feathers. These feathers are missing in feathered dinosaurs that are closely related to birds but aren’t quite birds. Their wing feathers stop at the elbow. That tells us that these non-avian dinosaurs couldn’t fly, but Archaeopteryx could. This also adds to evidence that suggests dinosaurs evolved flight more than once, which I think is super exciting.
Bottom line: An exquisitely preserved Archaeopteryx, on display at the Field Museum in Chicago, has revealed new details about how some dinosaurs evolved to become birds.
Source: Chicago Archaeopteryx informs on the early evolution of the avian bauplan
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The post How did dinosaurs become birds? This fossil offers insights first appeared on EarthSky.
