The permafrost of Russia’s Siberian heartland has yielded an array of impressive finds in recent years. Last September, a local resident wandering along the banks of a river in the republic of Yakutia discovered the roughly 50,000-year-old remains of an extinct lion cub almost perfectly preserved by the permanently frozen ground. In 2015, Russian scientists chanced upon the similarly well-preserved remains of two ancient lion cubs dubbed Uyan and Dina.

Now, the Siberian Times reports, Yakutia’s frigid ground has produced yet another revolutionary discovery: Two nematodes, or roundworms, preserved in the Arctic permafrost for around 40,000 years have allegedly come back to life after being “defrosted” by researchers. If proven true, the claim—newly catalogued in the journal Doklady Biological Sciences—would make the roundworms Earth’s oldest living animals, shattering the record for the longest time an animal can survive cryogenic preservation.

According to New Atlas’ Michael Irving, a team of Russian scientists working in collaboration with Princeton University found the viable specimens while analyzing more than 300 soil samples taken from the Arctic permafrost. One of the samples was retrieved from a squirrel burrow located in the Duvanny Yar outcrop and dates to about 32,000 years ago. The older sample, which dates to about 41,700 years ago, was found in a glacial deposit near the Alazeya River. Both nematodes are believed to be female.

Irving writes that the worms were initially stored in a lab kept at -4 degrees Fahrenheit. Later, the samples were defrosted in a petri dish alongside an enrichment culture designed to encourage their growth. After spending several weeks basking in their new 68-degree Fahrenheit environment, the nematodes, against all odds, began moving and eating.

“Our data demonstrate the ability of multicellular organisms to survive long-term (tens of thousands of years) cryobiosis under the conditions of natural cryoconservation,” the scientists said in a statement. “It is obvious that this ability suggests that the Pleistocene nematodes have some adaptive mechanisms that may be of scientific and practical importance for the related fields of science, such as cryomedicine, cryobiology, and astrobiology.”

Robin M. Giblin-Davis, a nematologist and acting director of the University of Florida’s Fort Lauderdale Research and Education Center, tells Gizmodo’s Ed Cara that the feat is theoretically possible. He said the worms, if “protected from physical damage that would compromise their structural integrity during their frozen internment, … should be able to revive upon thawing/rehydration,” but cautions that the team’s “ancient samples” could have been contaminated by contemporary organisms.

Although the Russian scientists acknowledge the possibility of such contamination, they believe it is unlikely. The team followed procedures designed to ensure complete sterility, according to the study, and claims that the depth at which the nematodes were buried—100 feet and 15 feet below the surface—eliminates the possibility of inclusion of modern organisms. As Science Alert’s Mike McRae explains, nematodes generally don’t burrow deep into the Siberian permafrost, as seasonal thawing only reaches a depth of about three feet.

This isn’t the first time researchers have purportedly resurrected long-dead organisms; in 2000, a team claimed to have revived 250 million-year-old bacteria, though this extraordinary claim requires more evidence before the scientific community will wholeheartedly accept it. Still, the new announcement, which centers on multicellular organisms rather than single-celled bacteria, marks a significant milestone for scientists. McRae reports that nematodes have previously been revived after 39 years of dormancy, while their close relatives, the tardigrade (or water bear), have been successfully revived after roughly 30 years on ice.

Byron J. Adams, a nematologist at Brigham Young University, tells Gizmodo’s Cara that the researchers’ claims are feasible, but he believes that further testing should be conducted to definitively assess the worms’ age. He is particularly interested in what the ancient worms might reveal about their species’ evolution, noting that “after 40 thousand years, we should expect to detect significant differences in evolutionary divergence between ancient and contemporary populations.”

If proven true, the new findings offer tangible hope for the resurrection of similarly ancient organisms. The return of the woolly mammoth may remain far in the future, but in the meantime, we have two 40,000-year-old roundworms to spark our dreams of a Pleistocene revival.