Scientists have concluded that a newly discovered species of mammals used all four limbs to hang from trees. (Courtesy of April I. Neander/University of Chicago/Reuters)

In dense Chinese forests populated by dinosaurs 160 million years ago, two furry critters resembling flying squirrels glided from tree to tree, showing that even in such a perilous neighborhood, early mammals had succeeded in going airborne.

Scientists have announced the discovery of fossils of two Jurassic Period gliding mammals so well preserved and complete that they show the winglike skin membranes the creatures employed while gliding between trees.

The two species, Maiopatagium furculiferum from Liaoning province and Vilevolodon diplomylos in Hebei province, come from an extinct early mammalian side branch.

These two and another apparent glider from about the same time that was described in 2006 were the vanguard of the mammalian air force. It was not until more than 100 million years later that bats, which use powered flight like birds, and more gliding mammals appeared, following the dinosaurs’ demise.

Mammals first appeared roughly 210 million years ago. These fossils underscore that early mammals were not merely cowering at the feet of dinosaurs but boasted a range of body plans and lifestyles. They included ­beaver-tailed swimmers, tree climbers, hoppers, burrowers and small carnivores that ate baby dinosaurs.

Maiopatagium furculiferum is one of two newfound fossils from 160 million years ago. (Courtesy of Zhe-Xi Luo/Beijing Museum of Natural History, University of Chicago/Reuters)

“Despite living in dinosaur-dominated ecosystems, early mammals diversified into many ecological niches,” said University of Chicago paleontologist Zhe-Xi Luo, who led the research, which was published in the journal Nature.

Gliding may have offered Maiopatagium and Vilevolodon advantages in gathering food and avoiding predators. They were unrelated to today’s four groups of gliding mammals: flying squirrels in North America and Asia, Africa’s scaly-tailed gliders, Australia’s marsupial sugar gliders and Southeast Asia’s colugos.

Maiopatagium was about nine inches long, similar in size to flying squirrels. Vilevolodon was a bit smaller. Maiopatagium’s teeth resembled those of fruit bats, suggesting it ate soft plant parts. Vilevolodon’s teeth were more like those of squirrels, good for eating seeds.

Judging from hand and foot bones, the scientists concluded that the two roosted, using all four limbs to hang from trees and gripping tree branches with their feet like bats.

— Reuters