A 160-million-year-old fossil was unearthed in China, giving researchers a look into an extinct species and its secret to successful evolution.

The fossil was of a rodent-like creature representing a multituberculates species known as Rugosodon eurasiaticus.  Its skeleton holds insight to traits that helped the animal survive, like teeth that were adapted to chew on plants and animals, and rotating ankle joints, according to a news release. 

The findings were published in the Aug. 16 issue of Science. The American Association for the Advancement of Science explained the scientists' analyses in a news release.

"The multituberculates flourished during the Cretaceous era, which ended over 60 million years ago. Much like today's rodents, they filled an extremely wide variety of niches-below the ground, on the ground and in the trees-and this new fossil, which resembles a small rat or a chipmunk, possessed many of the adaptations that subsequent species came to rely upon," the researchers said.

Multituberculates lived during the Jurassic period and were extinct by the Oligocene epoch, according to the news release.  They roamed the planet for more than 100 million years before evolution took over and "modern" rodents became superior.  The animals evolved "complex teeth" that allowed them to eat planet, and were able to live amongst treetops with their ankle joint adaptation. 

"The later multituberculates of the Cretaceous [era] and the Paleocene [epoch] are extremely functionally diverse: Some could jump, some could burrow, others could climb trees and many more lived on the ground," explained Zhe-Xi Luo, a co-author of the Science report. "The tree-climbing multituberculates and the jumping multituberculates had the most interesting ankle bones, capable of 'hyper-back-rotation' of the hind feet."

"What is surprising about this discovery is that these ankle features were already present in Rugosodon-a land-dwelling mammal," he said. (Such highly mobile ankle joints are normally associated with the foot functions of animals that are exclusively tree-dwellers-those that navigate uneven surfaces.)

Researchers believe the fossil they unearth is from the early station of evolution, the beginning stage for "diversification" between other rodent-like mammals.  

"This new fossil from eastern China is very similar to the Late Jurassic fossil teeth of multituberculates from Portugal in western Europe," explained Dr. Luo. "This suggests that Rugosodon and its closely related multituberculates had a broad paleogreographic distribution and dispersals back-and-forth across the entire Eurasian continent."