During the age of the dinosaurs, Myanmar’s Hukawng Valley was filled with trees that oozed sticky resin, which often trapped plants and small animals, preserving their remains for millions of years. Today, the Hukawng Valley is a veritable goldmine of fossils enshrined in amber, as the hardened resin is known; among the discoveries that have been made in the region are the oldest known bee and a dinosaur tail still covered in feathers.
Now, a new report in Current Biology describes a Hukawng Valley specimen that has both fascinated and puzzled experts. In 2014, Lida Xing of the China University of Geosciences obtained a fossil from amber traders, who thought the preserved remains belonged to an ancient lizard. Xing, however, knew it was a bird—one with bizarrely long toes.
“I was very surprised when I saw the amber,” Xing says. “It shows that ancient birds were way more diverse than we thought.”
Dating to around 99 million years ago, the fossil preserves part of the bird’s right hindlimb. According to the study authors, the creature’s body underwent substantial decay before it was encased in tree resin, with some of its skin sloughing off the foot bones and drifting through the amber. But Xing and his colleagues could still make out the shape of the bird’s foot, including its astonishingly lengthy third toes. When researchers scanned the amber with micro-CT and created 3D models of the foot, they found that the bird’s curious digits measured 9.8 millimeters, making them 41 percent longer than the animal’s next-longest toe. Sabine Galvis of Science likens the proportions to “having a toe as long as your shin.”
The team could tell that the bird belonged to an extinct avian family known as the Enantiornithes, which was the most abundant bird group in the Mesozoic era. But when researchers compared the bird’s foot to those of 20 other extinct birds from the period, they could not find any others with similarly hyper-long toes. Scientists also studied the feet of 62 existing birds. None had tootsies quite like the new specimen.
The researchers thus concluded that they had stumbled upon a new species, which they dubbed Elektorornis chenguangi—“elektorornis” meaning “amber bird.” Smaller than a sparrow, E. chenguangi was likely arboreal, meaning that it spent most of its time in trees, rather than on the ground or in water.
“Elongated toes are something you commonly see in arboreal animals because they need to be able to grip these branches and wrap their toes around them," explains Jingmai O'Connor, study co-author and paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. “But this extreme difference in toe lengths, as far as we know, has never been seen before."
Just how E. chenguangi used its hyper-elongated toes is unclear. The aye-aye, a Malagasy primate, is the only known animal with similarly disproportionate digits, and it relies on its toes to scoop insects and larvae out of trees. Perhaps, the researchers theorize, E. chenguangi fed in a similar way. Without any modern birds to compare it to, “[t]his is the best guess we have,” O'Connor says.
E. chenguangi’s unusual adaptation may have served it well for a time, but the species would have been wiped out with all other Enantiornithes when an asteroid slammed into the Earth 66 million years ago, according to Becky Ferreira of the New York Times. In the wake of the calamity, Neornithes, the family that includes all surviving birds, became dominant.
As the new study shows, amber fossils can offer revelatory glimpses into the animals that once populated our planet. But these fossils are controversial. As Joshua Sokol reported for Science in May of this year, the relics are mined in Kachin state, a conflict-ridden part of Myanmar where rival factions compete for the profits generated by amber and other natural resources.
“These commodities are fueling the conflict,” Paul Donowitz, campaign leader for Myanmar at Global Witness, told Sokol. “They are providing revenue for arms and conflict actors, and the government is launching attacks and killing people and committing human rights abuses to cut off those resources.”
Speaking to the Times’ Ferreira, O’Connor acknowledged the ethical concerns surrounding Myanmar’s amber fossils, but noted that “[i]t’s the conflict that has dragged the amber into it, not the other way around.” And the researchers behind the new study hope that the E. chenguangi fossil will continue to be important to scientific research. Moving forward, they plan to extract proteins and pigments from feathers that are exposed on the surface of the amber, with the goal of learning more about the life of this unique bird.