Mammals started flying when birds did

The first gliding mammal winged through forests at least 70 million years earlier than scientists had previously presumed, a new fossil shows. The specimen dates from about 150 million years ago, during the time when birds were developing flight.

“This changes our view about the early evolution of mammals,” says Jin Meng of the American Museum of Natural History in New York City. Scientists had proposed that mammals from that period “lived in the shadow of dinosaurs and were relatively primitive,” Meng says. He and his colleagues report the finding in the Dec. 14 Nature.

Farmers found the new fossil in Inner Mongolia last year. The creature weighed roughly a pound and was similar in shape to today’s flying squirrel. It soared on skin flaps stretching from its extra long arms to its gangly legs, which were covered with dense hair. The animal is one of the oldest in the fossil record to show fur, and it’s so different from any other known mammal that the researchers had to create a new genus, family, and order for it. The team named the creature Volaticotherium antiquus, or “ancient gliding beast.”

Since V. antiquus was so light and had large membranes for gliding, it must have swooped and turned nimbly. It steered with a long, stiff tail that acted as a rudder, say the researchers.

The creature has no known descendants or ancestors. Meng speculates that now that researchers know what to look for, they may soon discover some V. antiquus relatives.