Researchers have found fossils of three previously unknown species of squirrel-like animals that once lived in China.

The new study, published this week in the journal Nature, outlines the discovery supporting the idea that the earliest mammals may have originated 200 million years ago. That's millions of years earlier that previous research indicates, according to CBS News.

The new findings are expected to help scientists understand when and how these mammals diversified.

Researchers identified and described three new species, Shenshou lui, Xianshou linglong, and Xianshou songae, from six 160-million-year-old fossils found in China.

"They were good climbers and probably spent more time than squirrels in trees," study author Jin Meng, a curator in the Museum's Division of Paleontology, said in a statement, according to CBS News. "Their hands and feet were adapted for holding branches, but not good for running on the ground."

The new species dates back to the Jurassic period and has been assigned to a new, rare group of Euharamiyida. Researchers estimate that the animals weighted around 1 to 10 ounces and had tails and feet indicating that they were tree dwellers, according to the study.

They mainly ate insects, fruit, and nuts.

Based on the age of Euharamiyida, the divergence of mammals from retiles likely occurred much earlier than research suggests. The research means mammals likely first originated during the Triassic era, around 235 and 201 million years ago, and not in the middle Jurassic, between 176 and 161 million years ago.

"What we're showing here is very convincing that these animals [the three new species] are mammals, and that we need to turn back the clock for mammal divergence," Meng said. "But even more importantly, these new fossils present a new suite of characters that might help us tell many more stories about ancient mammals."

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