The known longest cave system in the world is Mammoth Cave in central Kentucky, United States, with 663 km of surveyed passageways.

The cave researchers conducted a joint expedition on March 11 at Shuanghe Cave, attracting more than 30 experts from China, France, Canada and Portugal.

Jean Bottazzi, a well-known French caver who had lived in China for several years to explore the country's underground kingdom, found a new tunnel in Shuanghe Cave connecting with Duiwo Cave, where the new lizardlike species was found.

Duiwo Cave was discovered in 2003 but wasn't explored until 2015 because of technical difficulties. It has been measured at 8 km long so far after three years of exploration.

Dong Xianwu contributed to this story.