An 80-million-year-old bird skeleton could tell us more about how the unique intelligence of modern birds evolved. © Stephanie Abramowicz
By Emma Caton
A remarkable fossil could transform our understanding of how the intelligence of modern birds evolved.
The 80-million-year-old complete skull of a bird is revealing more about the evolution of brain structure from the earliest known bird-like dinosaurs to modern birds.
A ‘one of a kind’ discovery could help solve one of the most enduring mysteries of vertebrate evolution – how birds developed their unique intelligence.
Researchers have identified an exceptionally well-preserved fossil bird dating back to the age of the dinosaurs. The skull has been preserved almost intact, which is rare for any fossil bird let alone for one so ancient.
The fossil bird, which has been named Navaornis hestiae, lived approximately 80 million years ago in what is now Brazil, before the mass extinction event that killed all non-avian dinosaurs. It was discovered by palaeontologist William Nava, for whom the species is now named after.
Scientists used advanced micro-CT scanning technology to digitally reconstruct the bird’s skull and brain in remarkable detail.
The researchers say their discovery, reported in the journal Nature, could help to determine the evolutionary origins of the modern avian brain. This is because the fossil fills a 70-million-year gap between animals such as Archaeopteryx and modern day crows.
Professor Daniel Field, a palaeontologist and coauthor of the study, says, “Modern birds have some of the most advanced cognitive capabilities in the animal kingdom, comparable only with mammals.”
“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.”
Navaornis represents an intermediate step in evolution between the first bird-like dinosaurs, such as Archaeopteryx, and living birds. © Júlia d’Oliveira.
As well as being exceptionally well-preserved, the discovery of this fossil has huge significance as the brain structure of Navaornis is almost exactly intermediate between Archaeopteryx and modern birds.
Before this latest fossil, knowledge of this evolutionary transition was practically non-existent.
It shows that Navaornis had a larger cerebrum than Archaeopteryx, suggesting it had more advanced cognitive capabilities than the earliest bird-like dinosaurs. However, most areas of its brain, like the cerebellum, were less developed, suggesting that it hadn’t yet evolved the complex flight control mechanisms of modern birds.
While Navaornis is one of the best-preserved bird fossils ever found from the Mesozoic Era, the researchers believe more finds from Brazil could offer further insights into bird evolution.
“This might be just one fossil, but it’s a key piece in the puzzle of bird brain evolution,” says Daniel. “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.”
The researchers say it is only the first step in understanding the evolution of bird intelligence.
Navaornis lived in a dry area with slow-flowing creeks. It would have shared this environment with other small animals, like lizards and other birds, as well as large dinosaurs. © Júlia d’Oliveira.
At first glance, Novaornis would probably have looked a lot like a living bird. It was about the size of a European starling, with a toothless beak and large eyes. But closer examination would have revealed features absent in living birds, such as claws protruding from the wings.
It is not certain what Navaornis would have been eating, but its bill would have allowed it to eat a wide range of items like invertebrates and seeds.
The fossil was discovered in Presidente Prudente, in the Brazilian state of São Paulo. During the Late Cretaceous, this site was likely a dry area with slow-flowing creeks. Navaornis would have shared this environment with other small animals, like lizards and other birds, as well as large dinosaurs.
Navaornis is a member of an extinct group of early birds called Enantiornithes, or the ‘opposite birds’. This group diverged from modern birds more than 130 million years ago, but had complex feathers and were likely competent flyers.
However, the brain anatomy of Navaornis poses a new question. Without an expanded cerebellum, it is uncertain how these birds manged to control their flight.
“This fossil represents a species at the midpoint along the evolutionary journey of bird cognition,” said Daniel. “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 behaviour.”
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