In the late 1970s, someone discovered two fossilized teeth in coal deposits in northwestern Bulgaria, then brought them to the Bulgarian National Museum of Natural History. Ivan Nikolov, the museum’s paleontologist at the time, cataloged the teeth, jotting down the word “Guredjia” on a handwritten label before stashing them away in the collection.
Now, decades later, paleontologists have finally unraveled the mystery of these long-forgotten teeth. They belonged to a newly identified species of panda that roamed Bulgaria’s swampy, forested regions around six million years ago during the Miocene Epoch. Researchers named the animal, the last known European giant panda, Agriarctos nikolovi in honor of the paleontologist who originally cataloged the teeth, according to a study published this week in the Journal of Vertebrate Paleontology.
Nikolai Spassov, a present-day paleontologist at the museum, found the coal-blackened upper carnassial tooth and upper canine in the museum’s archives, but couldn’t immediately make sense of the old handwritten label. Eventually, he determined that Guredjia was the old name for a village called Ognyanovo, located in northwest Bulgaria in the northern foothills of the Ihtimanska Sredna Gora mountains.
“It took me many years to figure out what the locality was and what its age was,” Spassov says in a statement. “Then it also took me a long time to realize that this was an unknown fossil giant panda.”
After studying the teeth more closely and comparing them to those of other bears, the researchers realized they’d stumbled upon a new species. Though A. nikolovi is likely a close relative of today’s giant pandas, they’re not direct ancestors, per Spassov.
Paleontologists were able to glean many important insights from the fossil teeth. For one, they suggest that A. nikolovi was roughly the same size or maybe slightly smaller than today’s giant pandas. The artifacts also indicate that the animals ate a mostly vegetarian diet, but not one that included bamboo; their teeth weren’t strong enough to crush bamboo’s woody stems, which leads the researchers to believe they likely ate softer plant materials instead. The teeth were, however, robust enough to ward off attacks from predators, according to the researchers.
A. nikolovi likely disappeared because of the Messinian salinity crisis, a mysterious event in which the waters of the Mediterranean dried up starting around six million years ago. The specialized pandas likely lost the humid, wooded habitats and the main sources of food they needed to survive.
Various giant pandas once roamed across Europe and Asia, however, today just one species remains: Ailuropoda melanoleuca. These iconic black-and-white bears munch on 26 to 84 pounds of bamboo each day while living high in the forested mountains of China. Once listed as "endangered," pandas are now considered "vulnerable," but they still remain at risk because of development and climate change. Today, 1,864 giant pands live in the wild, according to the World Wildlife Fund.
Scientists still aren’t sure where pandas originated—whether in Asia or in Europe—because they just don’t have enough fossils to form a complete picture of their evolution. One theory is that pandas originated in Asia, but traveled to Europe and continued evolving. Another suggests the opposite: That the bears developed in Europe and then arrived in Asia.
“We have a nice fossil record in Europe starting at least 11.6 million years ago, but we do not have a complete fossil record in Asia from the same time period,” David Begun, an anthropologist at the University of Toronto who was not involved in the study, tells NBC News’ Tom Metcalfe. “So it is impossible to say if they were there as well, but remain undiscovered.”
The newly discovered species reinforces just how little scientists know about “ancient nature” and demonstrates that “historic discoveries in paleontology can lead to unexpected results, even today,” says Spassov.