A giant flying squirrel the size of a house cat swooped through the skies of Southern Appalachia some 4.75 million years ago.
This is the revelation of a team of paleontologists from the East Tennessee State University (ETSU) and the Autonomous University of Barcelona (UAB), in Spain.
In their study, the researchers described a new fossil specimen of the giant flying squirrel Miopetaurista webbi recently unearthed from a veritable prehistoric treasure trove known as the Gray Fossil Site, located in Washington County, Tennessee.
Despite its size, the team explained, the giant squirrel would have weighed in at only around three pounds, helping it to glide and giving it agility as it skittered across the tree tops.
Contrary to what one might expect, however, Miopetaurista is not closely related to the squirrels we now see in North America; they have in fact more in common with the giant flying squirrels of China, Indonesia and Japan.
"It is amazing to imagine these giant flying squirrels gliding over rhinos and mastodons living in the forests of Tennessee 5 million years ago," said paper author Joshua Samuels of ETSU in a statement.
"This really points to the potential of the Gray Fossil Site to keep surprising us after 25 years."
Miopetaurista specimens have previously been unearthed from the Miocene and Pliocene (23.03–5.33 million and 5.33–2.58 million years ago, respectively) epochs of China, France and Germany.
"Finding Miopetaurista in North America was quite unexpected as this genus is only known from Eurasia," said UAB paper co-author Isaac Casanovas-Vilar in a statement.
"There had been some uncertain reports from Florida, but the specimen of the Gray Fossil Site provided new information and helped to confirm that, somehow, these giant flying squirrels crossed the Bering Land Bridge alongside other mammals about 5 million years ago."
This land bridge is hypothesized to have linked North America with Asia at various points in the past.
When Miopetaurista arrived in what we now know of as Tennessee, the researchers explained, the world was much warmer than it is today.
This climate supported dense, humid forests—in fact evidence for such, in the form of plant fossils, has also been found at the Gray Fossil Site—that would have allowed the critter to cross into North America, gliding from tree to tree.
Such agreeable conditions, however, were not to last for poor Miopetaurista.
"As the climate cooled over time, the Pleistocene Ice Ages led to the isolation of these giant flying squirrels in warmer refuges like Florida—and ultimately contributed to their extinction," said paper first author Montserrat Grau-Camats, also of the UAB, in a statement.
"The last American Miopetaurista lived millions of years after all Eurasian species of this genus had disappeared, meaning at the time they were 'living fossils.'"
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Reference
Grau-Camats, M., Casanovas-Vilar, I., Crowe, C. J., & Samuels, J. X. (2025). Gliding between continents: A review of the North American record of the giant flying squirrel Miopetaurista (Rodentia, Sciuridae) with the description of new material from the Gray Fossil Site (Tennessee). Journal of Mammalian Evolution, 32(1), 8. https://doi.org/10.1007/s10914-025-09751-w