Scientists have identified the oldest fossil ever found of a modern bird.
The fossil, found in a limestone quarry near the Belgian-Dutch border, dates from less than one million years before the asteroid impact which eliminated all large dinosaurs.
A research team, led by Cambridge University, identified a near-complete 66.7 million-year-old bird skull within the rock.
The skull combines many features common to modern chickens and duck-like birds, suggesting it may be close to the last common ancestor of modern chickens and ducks.
It has been colloquially nicknamed the Wonderchicken and formally named Asteriornis, in reference to Asteria, the Greek Titan goddess of falling stars.
Researchers used high-resolution X-ray CT scans to peer through the rock and view the skull just one millimetre beneath.
"The moment I first saw what was beneath the rock was the most exciting moment of my scientific career," said Dr Daniel Field from Cambridge's Department of Earth Sciences, who led the research.
"This is one of the best-preserved fossil bird skulls of any age, from anywhere in the world.
"We almost had to pinch ourselves when we saw it, knowing that it was from such an important time in Earth's history.
Co-author Albert Chen, a PhD student based at Cambridge, said: "The origins of living bird diversity are shrouded in mystery - other than knowing that modern birds arose at some point towards the end of the age of dinosaurs, we have very little fossil evidence of them until after the asteroid hit.
"This fossil provides our earliest direct glimpse of what modern birds were like during the initial stages of their evolutionary history."
The announcement of the Wonderchicken find coincides with a new exhibit at Cambridge's Sedgwick Museum of Earth Sciences, where visitors can learn more about Asteriornis and see the fossil up close.
"Dawn of the Wonderchicken" runs from March 19 to June 15, and admission is free.