The large skeleton was in pieces—and scientists in Spain initially thought in 2002 they had a primate from ancient times. Some paleoprimatologists monitoring the work eagerly awaited the scientific implications.
But further investigation into the very dirt around the bones determined that the remnants actually formed part of the fossil of a giant flying squirrel which dominated its ecological niche millions of years ago, as reported in the journal eLife yesterday.
“Due to the large size of the tail and thigh bones, we initially thought the remains belonged to a primate,” said Isaac Casanovas-Vilar, a research at the Institut Catala de Paleontologia Miquel Crusafont.
The best clue was noted in the tiniest details of what remained: specialized wrist bones for the rodent’s soaring activities. The miniscule fragments of the fossil only emerged when what was seen as “dirt” attached to the skeleton was screen washed carefully, according to the paper.
Those wrist bones presented a trove of data—and discoveries, according to the Spanish team.
“Its diagnostic wrist anatomy indicates that the two subtribes of flying squirrels had already diverged at that time,” they write. “Moreover, this new fossil allows for a recalibration of flying squirrel time of origin and diversification, generally providing somewhat older estimates than previous molecular analyses.”
The dating of Miopetaurista neogrivensis—an extinct flying squirrel—shows the fossil to 11.6 million years old. Data compared with other fossils, indicates that the critter was soaring the ancient Spanish forests for millions of years, with relatively few evolutionary changes, according to their analysis.
The extinct Miopetaurista evolved from tree squirrel ancestors between 31 and 25 million years ago—and millions of years earlier than previously believed, according to the scientists.
The extinct critter could reach almost four pounds, according to the skull-to-mass estimates. (For comparison, Eastern gray squirrels currently common in North America top out at just over 1 pound).
Current-day flying squirrels, which are scattered from 52 species across the globe, still exist today. Two species in the tropics and subtropics of Asia are close enough to “be considered living fossils,” according to the researchers.

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