New nearly intact fossil reveals roots of avian intelligence

Nov. 13. () –

The identification of a fossil bird from the Mesozoic the size of a starling can transform understanding of how modern birds’ unique brains and intelligence evolved.

The entire skull has been preserved almost intact: a rarity for any fossil bird, but particularly for one so old, making this one of the most significant finds of its kind.

The extraordinary three-dimensional preservation of the skull allowed researchers, led by the University of Cambridge and the Los Angeles County Museum of Natural History, to digitally reconstruct the brain of the bird, which they have named Navaornis hestiae. Navaornis lived approximately 80 million years ago in what is now Brazilbefore the mass extinction event that killed all non-avian dinosaurs.

The researchers say their discovery, published in the journal Nature, could be a kind of “Rosetta Stone” to determine the evolutionary origins of the modern avian brain. The fossil fills a 70-million-year-old gap in our understanding of how the bird brain evolved: between the 150-million-year-old Archeopteryx, the oldest known bird-like dinosaur, and birds living today.

Navaornis had a larger brain than Archeopteryx, suggesting it had more advanced cognitive abilities than the early bird-like dinosaurs. However, most areas of his brain, such as the cerebellum, were less developed, suggesting that it had not yet developed the complex flight control mechanisms of modern birds.

“The brain structure of Navaornis is almost exactly intermediate between Archeopteryx and modern birds; it was one of those moments where the missing piece fits absolutely perfectly,” he said. in a statement co-senior author Dr. Guillermo Navalón, from the Department of Earth Sciences at Cambridge.

The Navaornis fossil owes its name to William Nava, director of the Marília Museum of Paleontology, in the Brazilian state of São Paulo, who discovered it in 2016 at a site in the neighboring town of Presidente Prudente. Tens of millions of years ago, this site was probably a dry area with slow-flowing streams, which allowed for the exquisite preservation of the fossil.

This conservation allowed researchers to use advanced micro-computed tomography technology to reconstruct the bird’s skull and brain with an extraordinary level of detail.

ONE OF A KIND

“This fossil is truly one of a kind, and I was amazed from the moment I first saw it to the moment I finished assembling all the bones of the skull and brain, allowing us to fully appreciate the anatomy of this primitive bird,” Navalón said.

“Modern birds have some of the most advanced cognitive abilities in the animal kingdom, comparable only to those of mammals”, said Professor Daniel Field, from Cambridge’s Department of Earth Sciences, lead author of the research.

“But scientists have struggled to understand how and when the unique brains and remarkable intelligence of birds evolved; “The field has been waiting for the discovery of a fossil exactly like this.”

Before this discovery, knowledge of the evolutionary transition between the brains of Archeopteryx and modern birds was practically non-existent.

“This represents almost 70 million years of avian evolution in which all the major lineages of Mesozoic birds originated, including the first representatives of birds living today,” Navalón said. “Navaornis sits right in the middle of this 70-million-year gap and tells us about what happened between these two evolutionary points.”

While the skull of Navaornis looks a bit like that of a small pigeon at first glance, Closer inspection reveals that it is not a modern bird at allbut a member of a group of primitive birds called enantiornithines, or the “opposite birds.”

“The opposite birds diverged from modern birds more than 130 million years ago, but they had complex feathers and were probably competent flyers like modern birds. However, the brain anatomy of Navaornis raises a new question: how did they control their flight?” the opposite birds without the full set of brain features seen in extant birds, including an expanded cerebellum, which is the spatial control center of an extant bird?

“This fossil represents a species at the midpoint of the evolutionary journey of bird cognition“said Field, who is also the Strickland Curator of Ornithology at the Museum of Zoology, Cambridge. “Its cognitive abilities may have given Navaornis an advantage when it came to finding food or shelter, and it may have been capable of mating displays. elaborate actions or other complex social behavior.

“This discovery shows that some of the birds that flew over the heads of dinosaurs “They already had a completely modern cranial geometry more than 80 million years ago,” said co-senior author Dr. Luis Chiappe of the Los Angeles County Museum of Natural History.