The world's oldest known fossil primate skeleton –dating back 55 million years – has been discovered in China, scientists have announced.

Estimated to have weighed 20 to 30 grammes, the skeleton of the tiny long-tailed creature was unearthed in an ancient lake bed in central China's Hubei province, near the course of the modern Yangtze River.

Archicebus achilles is thought to have been active during the day, to have climbed trees and eaten insects.

The findings represent a decade of intensive research by scientists using expertise at museums throughout the world.

Lead researcher Xijun Ni, a scientist at the Chinese Academy of Sciences in Beijing, said in the journal Nature: "It represents a big step forward in our efforts to chart the course of the earliest phases of primate and human evolution."