In the latest Journal of Vertebrate Paleontology, researchers announced that they have found a massively diverse set of fossils in a northeast region of China called Inner Mongolia. This group of 160 million year old fossils they’re calling the Daohugou Biota includes pterosaurs and the oldest dinosaurs found with feathers. Also found were two curious mammals; one called Castorocauda lutrasimilis that may have used a flat tail to swim like a beaver and one that appears to be the oldest known mammal to glide like a flying squirrel. These findings, along with previously discovered fossils dating to 30 million years later, could give us valuable insight on what kind of evolutionary changes were taking place during this time frame.

Corwin Sullivan, lead author of the paper and an associate professor at the Institute of Vertebrate Paleontology and Paleoanthropology, said that “the Daohugou Biota gives us a look at a rarely glimpsed side of the Middle to Late Jurassic — not a parade of galumphing giants, but an assemblage of quirky little creatures like feathered dinosaurs, pterosaurs with advanced heads on primitive bodies, and the Mesozoic equivalent of a flying squirrel.”

The particular swimming style employed by today’s beavers may be an older stroke than we thought. (Mark A. Kingler/CMNH)

Rocky’s less friendly looking ancestor. (Chuang Zhao and Lida Xing)

Perhaps more impressive than the diversity of species found on this dig was the condition in which they were found. The remains were remarkably well preserved and included complete skeletons associated with intact feathers, fur, skin, and in the case of one curious salamander, a set of exterior gills. Yuan Wang, a co-author of the paper, pointed out that any evidence the soft tissues is immensely helpful in understanding how these animals evolved.

What I assumed were sweet dreadlocks are actually external gills on the salamander Chunerpeton. (Society of Vertebrate Paleontology)

These fossils are dated to 30 millions years before those of the Jehol Biota, which were found in roughly the same region and showed similarly high levels of biodiversity. Finding such rich caches of specimens in the same place but separated by so many years means that scientists can observe the evolutionary changes that may have taken place between these two time periods.

Want more dino-stories? Check out the Nerdist’s coverage of the sudden color burst scientists think occurred in feathered dinosaurs 150 million years ago.

Sources: Phys.org, DiscoveryNews