How an Ancient Fossil Bird Unlocked Secrets of Avian Evolution

Piecing together the bird brain evolution puzzle

When people ask me how I became a paleontologist, I always answer the same: Some children grow up into adulthood, and others become paleontologists. Ask anyone in my family, and they’ll tell you how accurate this is.

In fact, there’s something all children and paleontologists have in common: they all have a favorite dinosaur. Don’t trust me? Just read Dr. Andrea Corpolongo‘s recent story in my Medium publication Fossils et al.!

Fun fact: We just released a t-shirt for the publication’s fans!

And well, those who know me know that my answer to this question is Archaeopteryx, a transitional fossil between non-avian dinosaurs and avian dinosaurs (birds) from the Late Jurassic of Germany. But why Archaeopteryx you may ask? Well, because its discovery in 1861 started a revolution inside the field of paleontology, proving some old theories right, and completely changing our understanding of dinosaur and bird evolution.

In fact, it doesn’t happen that often, but from time to time, with patience in the field and the right technological resources, paleontologists make discoveries that either help us understand the evolution of life on Earth better or completely rewrite it.

This week, we saw one of these astonishing discoveries published in one of the most prestigious journals in natural sciences. The cherry on top is that I can count some of the study’s coauthors as good friends of mine, so I’m super excited to tell you more about the significance of this new fossil!

A fossil discovery in Brazil is reshaping what we know about the evolution of bird brains. But what’s so special about this fossil? The specimen, a Late Cretaceous bird called Navaornis hestiae, provides a unique glimpse into the evolutionary steps leading to the intelligent, behaviorally complex birds we see today.

But let’s look into it a bit more, shall we? Found in Presidente Prudente, São Paulo State, this remarkably preserved fossil might just fill a 70-million-year gap in the story of bird brain development.

This discovery addresses one of the long-standing mysteries in vertebrate evolution: How did birds develop such unique brains? And let me tell you, it’ not common to find a fossil that answers such an important mmystery

While the famous Archaeopteryx (150 million years old) shows the beginnings of bird-like traits, and modern birds display complex cognitive capabilities, the evolutionary steps in between have been unclear—until now.

“The brain structure of Navaornis is almost exactly intermediate between Archaeopteryx and modern birds—it was one of those moments in which the missing piece fits absolutely perfectly,” said Dr. Guillermo Navalón, co-lead author of the study.

However, there’s something fascinating about this research: the high-tech methodology they used.

The research team, led by scientists from the University of Cambridge and the Natural History Museum of Los Angeles County, used micro-CT scans to analyze the fossil in exquisite detail. These advanced imaging techniques allowed them to create a three-dimensional reconstruction of Navaornis’ skull and brain, highlighting features impossible to observe through traditional methods. Indeed, technology is taking over even the study of the most ancient species.

However, this state-of-the-art work revealed not just the anatomy of the skull but also clues about the bird’s neuroanatomy—what its brain looked like and how it functioned.

And so, what did the results of the study have to say?

The skull of Navaornis is both ancient and surprisingly modern. While it retains some primitive features typical of enantiornithines, a group of ancient birds where most of the members retained teeth and clawed fingers on each wing, it also shows significant overlap with the geometry of modern bird skulls.

This combination of traits makes Navaornis a crucial snapshot of evolution in action. “This fossil represents a species at the midpoint along the evolutionary journey of bird cognition,” said Professor Daniel Field, senior author of the research and a very good friend of mine.

One of the most surprising findings, though, is that Navaornis’ brain shows early signs of advanced cognitive abilities. Its cerebrum was larger than that of Archaeopteryx, hinting at improved problem: solving and social behaviors. However, the cerebellum, critical for precise flight control, was still relatively underdeveloped, suggesting that this bird wasn’t as skilled a flyer as today’s species.

I know what you’re thinking: Why is this important?

What makes Navaornis so remarkable isn’t just its age or preservation but its position in the evolutionary timeline. It bridges an enormous gap between Archaeopteryx and modern birds, providing context for how bird brains evolved.

“With Navaornis, we’ve got a clearer view of the evolutionary changes that occurred between Archaeopteryx and today’s intelligent, behaviorally complex birds like crows and parrots,” explained Dr. Field.

The fossil also raises fascinating questions about the evolution of flight. Enantiornithines like Navaornis were likely competent flyers, but their brain anatomy suggests they achieved flight with a different set of tools compared to modern birds.

How these ancient species managed to navigate and survive without the advanced spatial control provided by a fully developed cerebellum remains an open question.

Isn’t it fascinating how much we can infer about an extinct species from their brain anatomy?

However, while Navaornis alone cannot answer every question about bird evolution, it adds a critical piece to the puzzle. It shows that some features of modern bird brains and skulls were already taking shape more than 80 million years ago.

As Dr. Field noted, “This discovery shows that some of the birds flying over the heads of dinosaurs already had a fully modern skull geometry more than 80 million years ago.”

The Brazilian site where Navaornis was found is expected to yield even more discoveries, offering further insights into bird evolution. So, the authors of the study emphasize that this is just the start of what could be a transformative period for understanding how birds became the diverse and intelligent creatures they are today.

Navaornis hestiae fills a crucial gap in the evolutionary timeline, showing how bird brains developed over millions of years. Its intermediate traits, advanced enough to hint at early cognition but not fully modern, showcase the gradual assembly of the brain structures that define modern birds.

Additionally, this fossil underscores the value of cutting-edge technology in uncovering the secrets of life’s history. Indeed, Navaornis reminds us that even the smallest creatures can play a mighty role in helping us understand the mysteries of the past.