South African scientists claim to have uncovered the most complete skeleton yet of an ancient relative of man, hidden in a rock excavated from an archaeological site three years ago.

The remains of a juvenile hominid skeleton, of the newly identified Australopithecus (southern ape) sediba species, are the "most complete early human ancestor skeleton ever discovered", University of Witwatersrand palaeontologist Lee Berger said.

A South African scientist shows a tooth of Australopithecus sediba hidden in a rock excavated from an archaeological site three years ago. Also pictured is a copy of a skull of the same species that was discovered at the Malapa site in the Cradle of Humankind in 2009. Credit:AFP

The skeleton is thought to be about 2 million years old.

The upright-walking tree climber would have been aged between nine and 13 years when he or she died.