Scientists uncover 80-million-year-old ancient bird's brain structure

Scientists uncovered the ancient brain structure of an 80-million-year-old fossil bird named Navaornis hestiae, providing unprecedented insights into the evolution of avian intelligence. The fossil, discovered in Brazil, is remarkably well-preserved, allowing researchers to digitally reconstruct the bird's skull and brain in remarkable detail using advanced micro-CT scanning technology. This discovery fills a significant 70-million-year gap in understanding how the distinctive brains of modern birds evolved from their dinosaur ancestors.

Navaornis hestiae belongs to a group of primitive birds known as enantiornithines, which became extinct at the end of the Cretaceous period. The fossilized skull of Navaornis is almost perfectly intact, a rarity for such an ancient specimen, making it one of the most significant finds of its kind. The bird, roughly the size of a starling, lived alongside dinosaurs such as Tyrannosaurus and Triceratops during the Late Cretaceous in what is now Brazil.

The research team, led by the University of Cambridge and the Natural History Museum of Los Angeles County, used the extraordinary three-dimensional preservation of the skull to digitally reconstruct the brain of Navaornis hestiae with unprecedented detail. "This fossil is truly so one-of-a-kind that I was awestruck from the moment I first saw it to the moment I finished assembling all the skull bones and the brain, which lets us fully appreciate the anatomy of this early bird," said Dr. Guillermo Navalón, co-lead author of the study from Cambridge's Department of Earth Sciences.

"Navaornis hestiae fills a roughly 70-million-year-long gap in our understanding of how the distinctive brains of modern birds evolved," said Professor Daniel Field from the University of Cambridge, describing it as a Rosetta Stone for understanding bird brain evolution, as reported by New Scientist. The discovery provides the most complete glimpse to date of the brains of the ancestral birds that once flew above the dinosaurs.

The study revealed that while Navaornis hestiae had an enlarged cerebrum—the part of the brain associated with higher-level cognition—its cerebellum, responsible for complex flight control mechanisms, was not as developed as that of modern birds. This suggests that Navaornis may have possessed more advanced cognitive capabilities than the earliest bird-like dinosaurs, supporting a range of complex behaviors, but did not yet have the sophisticated flight control seen in today's birds.

"The bird's skull is strikingly modern looking. It gives you a very good understanding of the cranial anatomy of these early birds," Luis Chiappe, a paleontologist and curator at the Natural History Museum of Los Angeles County, commented, according to NPR. The researchers noted that at first glance, the skull resembles that of a small pigeon, but closer inspection reveals its primitive features as an enantiornithine.

"You probably would recognize it as a strange bird. It wouldn't look too out of place in the present day except if you look carefully at its wings, you might see that it had pointy claws protruding from them," Field added, according to NPR. He also noted that "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." 

The fossil was discovered in 2016 at a site in Presidente Prudente, São Paulo, Brazil, by William Nava, director of the Museu de Paleontologia de Marília, after whom the species is named. The near-perfect preservation is attributed to the environmental conditions of the site during the Late Cretaceous, which likely featured slow-flowing creeks that enabled exceptional fossilization.

"Navaornis sits right in the middle of this 70-million-year gap and informs us about what happened between these two evolutionary points," explained Dr. Guillermo Navalón, according to Agencia SINC. The researchers emphasize that while the discovery is significant, it is only the first step in understanding the evolution of bird intelligence. Future studies may reveal how Navaornis interacted with its environment, helping to answer broader questions about the evolution of bird cognition over time.

"This might be just one fossil, but it's a key piece in the puzzle of bird brain evolution," Field said The findings related to Navaornis hestiae help clarify the timing and order in which the distinctive neuroanatomical characteristics of birds evolved, offering new insights into one of the most enduring mysteries of vertebrate evolution.

Sources: New Scientist, IFLScience, Agencia SINC, NPR, Phys.org, Nature

This article was written in collaboration with generative AI company Alchemiq