Fossil From Age of Dinosaurs Reveals New Early Bird Species

Paleontologists have revealed a previously unknown species of early bird following the discovery of a remarkable "one-of-a-kind" fossil. The prehistoric species, named Navaornis hestiae, lived approximately 80 million years ago—before the mass extinction event that wiped out all non-avian dinosaurs, which occurred around 66 million years ago. The fossil specimen, described as "exquisitely preserved", was uncovered in 2016 at a site in the locality of Presidente Prudente, São Paolo state, Brazil. It has now been described as a new species in a study published in the journal Nature. Remarkably, the complete skull of the bird, which would have been roughly the size of a starling, has been preserved intact in three dimensions. This kind of preservation is rare for any fossil bird, but particularly one this old, making the discovery one of the most significant finds of its kind. Researchers hope the fossil will cast new light on how the unique brains and intelligence of modern birds evolved—an enduring mystery in the field of paleontology.

"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," study co-lead author Guillermo Navalón with the Department of Earth Sciences (DES) at the University of Cambridge said in a press release. "Modern birds have some of the most advanced cognitive capabilities in the animal kingdom, comparable only with mammals," Daniel Field, a senior author of the study with the DES, said in the release. "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." A dearth of three-dimensional fossils from the Mesozoic Era—a geologic period that lasted from around 252 million years ago to 66 million years ago—has long hindered our understanding of the origin of the distinctive skull and brain of modern birds. But the discovery of Navaornis represents a golden opportunity to glean insights into this evolutionary question, given that it is one of the best-preserved bird fossils ever found from the Mesozoic. The extraordinary preservation of the fossil even enabled the researchers to digitally reconstruct the bird's skull and brain in remarkable detail.

"[Navaornis] fills a roughly 70-million-year gap in our understanding of avian brain evolution, which witnessed major changes in the proportions and geometry of the avian brain culminating in the brains of living birds, which support a level of cognitive prowess and behavioral complexity rivaled only by mammals among living animals," Field told Newsweek. Prior to this find, the knowledge of the evolutionary transition between the brain of the 150-million-year-old Archaeopteryx—the earliest bird-like dinosaur—and modern birds was practically non-existent. "This represents nearly 70 million years of avian evolution in which all the major lineages of Mesozoic birds originated—including the first representatives of the birds that live today," Navalón said. "Navaornis sits right in the middle of this 70-million-year gap and informs us about what happened between these two evolutionary points." After analyzing the fossil, the researchers found that Navaornis likely had a larger cerebrum—the largest part of the brain, located at the top and front of the skull—than Archaeopteryx. This indicates that it had more advanced cognitive capabilities. However, other evidence suggests that it had not yet evolved the complex flight control mechanisms of modern birds. "The brain structure of Navaornis is almost exactly intermediate between Archaeopteryx and modern birds—it was one of these moments in which the missing piece fits absolutely perfectly," Navalón said.

At first glance, the skull of Navaornis appears to be similar to that of a small modern-day pigeon. However, investigations revealed that the species belongs to a group of early birds known as the "enantiornithines" or "opposite birds." Enantiornithines are a highly diverse group of Mesozoic Era birds that went extinct around 66 million years ago alongside all non-avian dinosaurs. They are not direct ancestors of modern birds but represent a side branch of avian evolution. Modern birds evolved from a separate lineage within the broader group of avian and non-avian dinosaurs. While enantiornithines diverged from modern birds around 130 million years ago, they are known to have shared certain traits, such as complex feathers and the ability to fly. "Opposite birds" also retained more primitive reptilian traits, such as teeth in their beaks and clawed fingers on their wings. The latest study has shed light on these Mesozoic creatures' cognitive capabilities. "[Navaornis] represents a species at the midpoint along the evolutionary journey of bird cognition," said Field, the Strickland Curator of Ornithology at Cambridge's Museum of Zoology. "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." Update 11/13/24, 12:38 p.m. ET: This article was updated with additional information and images. Update 11/13/24, 3:57 p.m. ET: This article was updated with comment from Daniel Field. Do you have an animal or nature story to share with Newsweek? Do you have a question about paleontology? Let us know via science@newsweek.com.

Reference

Chiappe, L. M., Navalón, G., Martinelli, A. G., De Souza Carvalho, I., Rodrigo, M. S., Wu, Y., & Field, D. J. (2024). Cretaceous bird from Brazil informs the evolution of the avian skull and brain. Nature. https://doi.org/10.1038/s41586-024-08114-4