The almost perfectly preserved skull of a prehistoric bird could be a sort of “Rosetta Stone” for understanding the evolution of avian intelligence — a process that has been a mystery until now. 

The research team determined the bird — Navaornis hestiae — was from the Mesozoic Era (about 252 million to 66 million years ago) and was roughly the size of a starling. The bird likely lived around 80 million years ago and died out before the fifth mass extinction event that wiped out most non-avian dinosaurs.

According to the study published in the journal Nature, this fossil fills a 70-million-year gap in understanding how bird brains evolved from the earliest known avian-like dinosaur, the Archaeopteryx (that lived 150 million years ago), to modern-day birds. 

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A Prehistoric Brain Scan 

After the initial discovery in Brazil in 2016 by William Nava (the fossil’s namesake), the director of the Museu de Paleontologia de Marília in Brazil’s São Paolo State, researchers from Cambridge University in the U.K. and the Natural History Museum of Los Angeles County in the U.S. could render 3D scans of the bird’s skull and reconstruct it’s brain.

“The brain structure of Navaornis is almost exactly intermediate between Archaeopteryx and modern birds,” said Guillermo Navalón from Cambridge’s Department of Earth Sciences and co-lead author of this study in a press release. “It was one of these moments in which the missing piece fits absolutely perfectly.” 

According to the study, Navaornis’ cerebrum was larger than Archaeopteryx, meaning it may have been more cognitively advanced. However, the research team also noted that other areas of Navaornis’ brain, like the cerebellum, were not as developed, so it may not have been able to fly as well as modern birds. 

“Modern birds have some of the most advanced cognitive capabilities in the animal kingdom, comparable only with mammals,” said Daniel Field from Cambridge’s Department of Earth Sciences and senior author of the study. “But scientists have struggled to understand how and when the unique brains and remarkable intelligence of birds evolved — the field has been awaiting the discovery of a fossil exactly like this one.”

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Opposite Birds 

When the team first examined Navaornis’ skull, they thought it resembled a pigeon’s skull. However, after a closer look, researchers determined Navaornis was part of a group known as enantiornithines, also known as opposite birds.

About 130 million years ago, opposite birds branched off from modern birds. They still had complex feather patterns and could fly well. These creatures often had teeth and small claws on the ends of their wings. 

After looking at Navaornis’ brain, researchers were left wondering how the species could fly since its cerebellum wasn’t fully developed. Today, modern birds use their cerebellum as their spacial control center. 

“This fossil represents a species at the midpoint along the evolutionary journey of bird cognition,” said Field in a press release. “Its cognitive abilities may have given Navaornis an advantage when it came to finding food or shelter, and it may have been capable of elaborate mating displays or other complex social behavior.”

While there is only one Navaornis fossil, researchers are hopeful that the information they can garner from it will clear the way to understand how modern birds evolved from their prehistoric forbears. The team believes there is still more to gain from the dig site where Navaornis first emerged.

“This might be just one fossil, but it’s a key piece in the puzzle of bird brain evolution,” said Field in a press release. “With Navaornis, we’ve got a clearer view of the evolutionary changes that occurred between Archaeopteryx and today’s intelligent, behaviourally complex birds like crows and parrots.”

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A graduate of UW-Whitewater, Monica Cull wrote for several organizations, including one that focused on bees and the natural world, before coming to Discover Magazine. Her current work also appears on her travel blog and Common State Magazine. Her love of science came from watching PBS shows as a kid with her mom and spending too much time binging Doctor Who.