Land was home to a menagerie of dinosaurs, amphibians and even some of the oldest, now-extinct mammals.
When you think about the Jurassic Period, you probably think of massive, lumbering dinosaurs. But they likely shared their airspace with smaller, furrier creatures.
Fossils of two extinct mammals that lived in what is now China some 160 million years ago revealed the outlines of wing-like membranes joining the rodent-like animals' front and hind limbs, a team of United States and Chinese scientists wrote in the journal Nature.
Paleontologists believe that it was two kinds of flying creatures - Maiopatagium furculiferum, discovered in Liaoning province, and Vilevolodon diplomylos of Hebei province.
Maiopatagium and Vilevolodon were found in the same rock formation in northeast China, where the fine sediment of a shallow Jurassic freshwater lake preserved them in excellent condition. Prof Zhe-Xi Luo, from the University of Chicago, US, said: "These Jurassic mammals are truly the first to glide". "Not only did these fossils show exquisite fossilization of gliding membranes, their limb, hand and foot proportion also suggests a new gliding locomotion and behavior". The fossils also showed that the bones in forelimbs were proportioned similarly to the bones in other known gliders, and the shoulders were seemingly created to maximize mobility-a must-have for being able to glide through the sky on extended arms.
Fossils with the remains of the dermal membrane, helping the animal to plan, scientists have discovered in China.
It is a long instated fact that dinosaurs existed millions of years ago. Those membranes apparently stretched down to the wrists and ankles of each species, a configuration similar to that seen in many of today's "flying" mammals.
Gliding is different from powered flight which involves flapping wings, as employed by birds and bats.
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Gliding mammals today include flying squirrels, lemurs and possums. Maiopatagium's teeth resemble those of fruit bats, suggesting it ate soft plant parts.
"Mammals are more diverse in lifestyles than other modern land vertebrates, but we wanted to find out whether early forerunners to mammals had diversified in the same way", added Luo. After all, which is easier: climbing down from your tree, walking through the underbrush (which could be home to any number of predators) and climbing up another tree; or just gliding from one tree to another?
Their gliding ability would have given them access to food that ground-bound competitors could not reach, said the team. It's the same reason that some modern-day tree-dwelling mammals evolved the ability to glide, Luo says.
They were the earliest known mammalian gliders, having evolved the ability 100 million years before the first modern mammals adopted the same technique.
The animals come from a dead-end evolutionary branch, because it was wiped out at the same time as the dinosaurs. Recently, though, a series of new discoveries - including these two gliding mammals - serve as evidence that there was actually far more variation in mammalian lifestyles at this time than previously thought. "They did their own evolutionary experiment to glide".
"It's wonderful that the aerial adaptions occurred so early in the history of mammals", said David Grossnickle, a graduate student at the University of Chicago in the US.
"We need to completely rethink the community structure and ecological relationships of the Mesozoic, especially with regards to how mammals fit into it", Polly says.