The world's oldest known fossil primate skeleton, a previously unknown genus, was unearthed from an ancient lakebed in central China, paleontologists say.

The journal Nature reports the new fossil provides insights into a pivotal event in primate and human evolution, the evolutionary divergence between the lineage leading to modern monkeys, apes and humans on the one hand and that leading to living tarsiers on the other.

"It represents a big step forward in our efforts to chart the course of the earliest phases of primate and human evolution," said Xijun Ni of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences in Beijing.

The tiny skeleton of Archicebus Achilles, representing both a new genus and new species, is about 7 million years older than the oldest fossil primate skeletons known previously, researchers said.

"Archicebus differs radically from any other primate, living or fossil, known to science," Christopher Beard of the Carnegie Museum of Natural History in Pittsburgh said. "It looks like an odd hybrid with the feet of a small monkey, the arms, legs and teeth of a very primitive primate, and a primitive skull bearing surprisingly small eyes. It will force us to rewrite how the anthropoid lineage evolved."