Scientists have uncovered two fossils of gliding mammals from the Jurassic Period that are so well-preserved and complete, you can even see the skin membranes that acted as wings as the creatures glided through the treetops. The animals are believed to be 160 million years ago and were found in what would have been dense forests in modern day China.

The two species, Vilevolodon diplomylos in Hebei Province, and Maiopatagium furculiferum in nearby Liaoning Province, are from an early mammal side branch in evolution that have since gone extinct.

Scientists think mammals appeared about 210 million years ago, so these are relatively early examples. The find shows that early mammals were quite distinct and had many adaptations to survive such a harsh and unforgiving world.

“Two 160 million-year-old mammal fossils discovered in China show that the forerunners of mammals in the Jurassic Period evolved to glide and live in trees,” the statement from the University of Chicago Medical Center reads. “With long limbs, long hand and foot fingers, and wing-like membranes for tree-to-tree gliding, Maiopatagium furculiferum and Vilevolodon diplomylos are the oldest known gliders in the long history of early mammals.

“The new discoveries suggest that the volant, or flying, way of life evolved among mammalian ancestors 100 million years earlier than the first modern mammal fliers. The fossils are described in two papers published this week in Nature by an international team of scientists from the University of Chicago and Beijing Museum of Natural History.”