A team of paleontologists from the USA and Catalonia (Spain) has described a new fossil specimen of the giant flying squirrel genus Miopetaurista from the Gray Fossil Site in Tennessee, dating back to the Early Pliocene epoch, approximately 4.9-4.5 million years ago. This discovery, published in the Journal of Mammalian Evolution, represents the oldest known occurrence of this genus in North America and provides valuable insights into the biogeography and evolution of flying squirrels. 

The fossil, identified as Miopetaurista webbi, is just a single lower third molar. This finding is significant because it extends the known range of Miopetaurista, a Eurasian giant flying squirrel, into North America and raises intriguing questions about how these large flying squirrels dispersed across continents. Miopetaurista was a successful group of flying squirrels in Eurasia, with numerous species ranging from Portugal to China throughout the Miocene and Pliocene epochs. 

Image 1. 3D model of the left molar of M. webbi curated at the collections of the Gray Fossil Site & Museum (extracted from Grau-Camats et al. 2025) 

Montserrat Grau-Camats, a researcher at the Institut Català de Paleontologia Miquel Crusafont (ICP), and co-author of the study, explains: "The presence of Miopetaurista in eastern North America is puzzling, as it is distant from the known geographical range of the genus and that of its sister taxon, the extant Petaurista. Our research suggests that Miopetaurista, which was associated with warm forested environments, may have dispersed into North America via the Bering Land Bridge during the warm phases of the Early Pliocene." 

While there are flying squirrels living in Appalachian forests today, those are not closely related to the newly discovered fossils. Instead, the extinct Miopetaurista is most closely related to the living giant flying squirrels (Petaurista) of southeast Asia, Japan and Indonesia. Miopetaurista would have been about twice as large as tree squirrels living in the area today. While about the same size as a house cat, the lightly built bodies of the squirrels would have weighed about 1.5 kilograms. 

About 5 million years ago, the world was much warmer than today, allowing Miopetaurista to disperse into North America across the Bering Land Bridge. The giant flying squirrels spread across the continent, where fossils have been recovered from Tennessee and Florida. The Gray Fossil Site records a warm, wet forest environment, ideal habitat for the new immigrant squirrels from Eurasia. As climates cooled, these squirrels became isolated in warmer refuges, such as Florida, until their eventual extinction during the Early Pleistocene (about 2.6 million years ago). 

Dr. Joshua X. Samuels, a co-author of the study, comments: "It is amazing to imagine these giant flying squirrels gliding over rhinos and mastodons living in the forests of Tennessee 5 million years ago. This really points to the potential of the Gray Fossil Site to keep surprising us after 25 years.". The Gray Fossil Site, where the specimen was found, has yielded a diverse array of plant and animal fossils, providing a detailed record of Early Pliocene life in the southern Appalachian region. The site represents an ancient warm-temperate forest ecosystem, with plant communities similar to those found in the southeastern US today. 

This research not only expands the knowledge of flying squirrel evolution and distribution but also contributes to our understanding of past climates and ecosystems in North America. 

The study was conducted by an international team of researchers, including Montserrat Grau-Camats and Isaac Casanovas-Vilar from the ICP, and Cheyenne J. Crowe and Joshua X. Samuels from East Tennessee State University, in the United States. This research is part of the R+D+I project PID2020-117289GBI00, funded by the Agencia Estatal de Investigación of the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033/). Additional support was provided by the Generalitat de Catalunya through the CERCA Programme. Casanovas-Vilar is a member of the consolidated research group 2021 SGR 00620 GR, funded by the Agència de Gestió d’Ajuts Universitaris i de Recerca of the Generalitat de Catalunya (AGAUR). Fossil specimen collection at the Gray Fossil Site in Tennessee was partially funded by a National Science Foundation Grant (NSF Grant #0958985). Further funding was provided by the Center of Excellence in Paleontology at East Tennessee State University and an ETSU RDC Major Grant (#23-011M) to Samuels. 

Main image: Recreation of life appearance of a giant flying squirrel genus Miopetaurista (Oscar Sanisdro / Institut Català de Paleontologia Miquel Crusafont).

Reference article: 

• 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, 8. https://doi.org/10.1007/s10914-025-09751-w