December 13, 2006
Mammals May Have Flown Before Birds
NEW YORK - A new fossil discovery from China shows that a tiny squirrel-like creature glided through the air during the age of dinosaurs, more than 75 million years earlier than scientists had documented that ability in a mammal.
The creature might have even beaten birds into the air.Like today's flying squirrels, it stretched a furry membrane between its limbs to provide an airfoil for gliding after it jumped from a tree. But it's not related to anything living today.
Scientists don't know exactly when the animal lived. Its remains could be anywhere from 130 million to 164 million years old, said Jin Meng of the American Museum of Natural History. He and colleagues from Beijing report the discovery in Thursday's issue of the journal Nature.
So it's clearly older than the 51 million-year-old bat that used to be the oldest evidence of flying or gliding in a mammal. And it has a chance of preceding the earliest known bird, Archaeopteryx, which flew about 150 million years ago.
It is much younger than flying reptiles called pterosaurs, which are dated from 230 million years ago.
Still, added to a recent find in the same locale in northeastern China that revealed a semi-aquatic creature, the discovery shows that early mammals were a lot more varied than the land-loving creatures scientists have traditionally envisioned, Meng said.
He and colleagues dubbed the animal Volaticotherium antiquus, which is Latin and Greek for "ancient flying (or winged) beast."
They believe it was nocturnal, like other mammals of the time were thought to be, and like gliding mammals are today. It was the size of a flying squirrel or a bat - less than three ounces. Its stiff tail might have been longer than the trunk of its body.
The find includes not only bones, but also impressions left in rock that reveal the furry membrane the creature used for gliding. Its teeth show it ate mostly insects, researchers said. But it probably couldn't hunt insects while gliding because it was too clumsy a flier and couldn't stay airborne long enough, researchers said.
So why glide? It's hard to draw conclusions for this creature specifically, Meng said, but in general, scientists think that gliding is an energy-saving way to get from tree to tree, compared to repeatedly climbing up and down trunks. Gliding probably increased the foraging range of the creature and maybe helped it escape predators in the trees, he said.
Larry Heaney, curator of mammals at the Field Museum in Chicago who has long studied gliding mammals, said the new creature "has taken the first step" toward powered flight like a bat exhibits.
But from its anatomy, "I would say this animal probably was not very far along the path to true flight," Heaney said. "It was not on the road to the kinds of modifications we see in bats that allow them to actually fly."
Meng said it's not clear whether descendants of the creature gained the ability to fly.
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