Oldest modern bird fossil looks like a duck from the back and a chicken from the front
Go to a Cajun restaurant in New Orleans, and you might be offered a slice of turducken: a fancy dish of chicken stuffed inside of a duck stuffed into a turkey. Now, paleontologists have their own version: the oldest modern bird skull ever found, which predates the split between the duck lineage and that of both chickens and turkeys—and so has traits of all three.
“This is an incredibly informative specimen,” says Amy Balanoff, a paleontologist at Johns Hopkins University, Baltimore, who wasn’t involved in the work. Whereas the earliest birds, like the 150-million-year old Archaeopteryx, look very different from today’s, the new fossil has clear characteristics of modern land and waterfowl, perhaps offering a glimpse of their common ancestor. Discovered near the Dutch town of Maastricht, in famous fossil beds that formed between 66.8 million and 66.7 million years ago, the turducken lived just before the mass extinction that killed off the dinosaurs. And because at least some of its descendants survived the cataclysm, “it gives us some clues about what characteristics were key in surviving that event,” Balanoff says.
Luck and technology prompted the find, says Daniel Field, a paleontologist at the University of Cambridge, who led the work. John Jagt, a curator at the Maastricht Natural History Museum, had spotted “four very small blocks of rock with broken limb bones poking out” in the museum’s collection, Field says. “It’s hard to imagine a less exciting looking fossil.” Just the same, Field and his postdoctoral fellow Juan Benito put the rock into a computed tomography scanner, hoping the x-rays would reveal the structures inside. When they saw the scan, Field says, their shouts made the technician run back into the room. “She thought we had broken the machine.”
The scan revealed a complete skull of what looked like a modern bird. The bones in the top and the back of the head closely resemble those of modern ducks, whereas the face and beak have unfused bones, as seen in today’s chickens and turkeys. “You can play this game all day: ‘Oh, it’s a duck! No, it’s a chicken!’” Field says.
Most of the bird’s body is missing, but a piece of leg bone suggests it had long legs for its head size. Combined with the fact that the Maastricht deposits formed in a shallow sea, the fossil’s proportions suggest it was a small shorebird, about the size of a modern seagull.
In a Nature paper this week, Field and his colleagues named the bird Asteriornis maastrichtensis, for Asteria, the Greek goddess of falling stars who turns herself into a quail. The falling stars nod to the asteroid impact and extinction that struck not long after the bird lived. Some scientists had argued that modern birds evolved in the Southern Hemisphere because the oldest modern bird fossils found until now came from Antarctica. But the new fossil is likely older than the Antarctic ones, arguing against that assumption.
The ability to look inside the intact rock was crucial to the discovery, Field says. The skull is less than 1 millimeter away from the femur, so “if we had started chipping away, we would have destroyed the skull.” So was the team’s willingness to gamble on an unassuming rock, he adds. “We have to be more hopeful in our collecting.”