​Beijing, May 18 (IANS) Chinese scientists have found fossils of the world's oldest known multi-cellular organisms, dating back as far as 1.56 billion years, nearly one billion years earlier than previously estimated.

The research published on Wednesday in the journal "Nature Communications" showed the fossils were found in carbon-rich compressions in China's Hebei province. The biggest was 30 cm long and eight cm wide, Xinhua news agency reported.

Zhu Maoyan, the lead researcher, said the Yanshan Mountain region has Mesoproterozoic sedimentary mudstone. Organic fragments extracted from the host rock show well-preserved multi-cellular cell structures.

Zhu said multi-cellular life with modest diversity existed in the early Mesoproterozoic seas, but the species' affinity to extant species remains unclear.

"Further research will shed light on the ancient marine ecosystem," he said.

Prior to this discovery, fossils of multi-cellular life only dated back some 600 million years.

The new fossils show organisms large enough to be visible to the naked eye and predate the diversification of multi-cellular life by nearly one billion years.​