A reconstruction of an extinct flying squirrel, Miopetaurista, from Europe that was likely similar to the squirrel found in the U.S. (Photo courtesy of Oscar Sanisidro)
Giant flying squirrels, comparable in size to a house cat, roamed North America about 5 million years ago, scientists have discovered after analyzing an unusual fossil found in an ancient sinkhole.
Scientists discovered the flying squirrel fossil among animal remains found in Tennessee 25 years ago. The specimen belongs to the extinct genus Miopetaurista, which is more common in Asia, although there are two suspected specimens from Florida, according to a study published Feb. 21 in the Journal of Mammalian Evolution.
“It's amazing to imagine these huge flying squirrels gliding over the rhinoceroses and mastodons that roamed the Tennessee forests 5 million years ago,” said study co-author Joshua Samuels, an associate professor of earth sciences at East Tennessee State University.
The research team suggests that Miopetaurista moved to North America when the continent connected to Asia via the Bering Land Bridge in the early Pliocene (5.3 to 2.6 million years ago). According to the study, Miopetaurista would have found warm forests like those found in modern-day Tennessee, which were similar to forests in Asia at the time.
This specimen of Miopetaurista was identified from a single tooth found at the Gray Fossil Site in East Tennessee. Other fossils from the site show that the region was full of unusual fauna when Miopetaurista lived.
Scientists continue to study the history of flying squirrels, which have an incomplete fossil record. The earliest North American specimens date back about 36 million years. However, flying squirrels disappeared from the fossil record about 9 million years ago before apparently reappearing with Miopetaurista in Florida about 4 million years ago, according to the study.
The Gray fossil site discovery is about a million years older than the two fossils found in Florida, making the find potentially the oldest Miopetaurista fossil ever discovered in North America to date.
The Gray Fossil Site sinkhole formed and filled with water about 5 million years ago. Surrounded by forest, the pond became a source of drinking water for many ancient species. Sediment and mud then gradually filled the pond, burying and preserving the animals that died there, according to East Tennessee State University.
Miopetaurista weighed about 3.3 pounds (1.5 kilograms), which is significantly heavier than the flying squirrels found in Tennessee today. For example, the northern Tennessee flying squirrel (Glaucomys sabrinus) weighs only 2.5 ounces (71 grams), according to the Tennessee Wildlife Resources Agency.
Miopetaurista thrived in what is now Tennessee until its warm ecosystems began to cool at the beginning of the Pleistocene about 2.6 million years ago. The Pleistocene brought ice ages, which likely drove Miopetaurista south to warmer regions like Florida, scientists say.
“As the climate gradually cooled, the Pleistocene ice ages isolated these giant flying squirrels in warmer refuges like Florida, which ultimately played a role in their extinction,” said study co-author Montserrat Grau-Camats, a researcher at the Catalan Institute of Paleontology in Spain.
Sourse: www.livescience.com
