In the bustling amber markets of Myanmar, a paleontologist named Lida Xing has collected tiny golden time capsules containing prehistoric insects, a baby snake and most famously a dinosaur’s feathered tail. One day in 2014, a bead seller’s wares caught his eye.
“I noticed that there was a very small bird foot in one of the beads, which made me very excited,” said Dr. Xing, who works at the China University of Geosciences in Beijing.
After some quick negotiations, Dr. Xing swooped up the specimen, a grisly, dismembered claw suspended in the beautiful honey-colored bead, which he called “Ugly Foot.” With the 99-milion-year-old amber bead now in his possession, Dr. Xing and his colleagues studied and CT-scanned the entombed appendage. They saw that the top of the foot was coated in fuzzy feathers. Closer inspection revealed that there were bristlelike feathers protruding from the tops of the toes.
“Feathered birds or feathered dinosaurs with feathered feet have been something that scientists have been looking for decades,” said Jingmai O’Connor, a paleontologist from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences in Beijing.
The finding, published last month in the journal Scientific Reports, offers clues to better understanding how the feet of birds and their extinct relatives have changed over time, the scientists said. It also contributes to the study of the evolutionary transition that occurred among dinosaurs, prehistoric birds and the birds we see flying around today.
Instead of “Ugly Foot,” the team bestowed upon their fuzzy bird foot a more endearing nickname.
“This specimen we called ‘Hobbit Foot’ because hobbits are known for having really hairy feet,” Dr. O’Connor said.
The “Hobbit Foot” belonged to a member of a now extinct group of birds called enantiornithines, which were prehistoric relatives of living birds. Unlike most modern birds, many enantiornithines — or “opposite birds” — had beaks with teeth and claws protruding from their wings. They also lacked fanned tails.
The reason paleontologists thought prehistoric birds with feathered feet existed, Dr. O’Connor said, was because we had seen traces of their fluffy feet in present-day birds.
Barring a few exceptions like snowy owls, ptarmigans, special chicken and pigeon breeds and some others, most living birds have featherless feet covered in scales. The scales on the top of their feet are different from the scales on the bottom. The top ones overlap, sort of like fish scales, while the bottom ones instead resemble dinosaur scales.
Paleontologists think the ancestors of birds began with scaly feet. Eventually, the scales on the top of the feet evolved into feathers. But they later reverted back into scales. The scales on the bottom of the feet did not undergo this change and instead stayed primitive. These changes, scientists think, explain the differences we see in the top and bottom scales of some modern bird feet. The newly discovered feathered foot in amber, the researchers said, provides support to their picture of the evolution of these foot scales.
The research was not without its challenges, said Ryan McKellar, a paleontologist at the Royal Saskatchewan Museum in Canada, and an author on the paper.
The team thinks the bird’s leg had been ripped from its body by either a hungry predator or scavenger before being coated by oozing tree resin. But it was not trapped alone. Nearly touching the foot was a wing, presumably belonging to the same bird. In order to get a closer look at the feathered foot, the team needed to slice the amber bead, which was only about the size of a dried apricot.
“Basically we had to saw through the amber within a three or four-millimeter window,” said Dr. McKellar. “It was one of those gut-wrenching moments.”
After an hour, Dr. McKellar successfully cut the amber in half, giving the team a clear view of their precious “Hobbit Foot.”