The remains of the juvenile hominid skeleton, of the 'Australopithecus sediba' species, hidden in a rock excavated three years ago constitute the "most complete early human ancestor skeleton ever discovered," said University of Witwatersrand paleontologist, Lee Berger.
The latest discovery by South African scientists was made in a three-foot wide rock that lay unnoticed for years in a laboratory until a technician noticed a tooth sticking out of the black stone last month.
"I was lifting the block up, I just realised that there is a tooth," said technician, Justin Mukanka.
The rock was then scanned to reveal significant parts of an A sediba skeleton, dubbed Karabo, whose other parts were first uncovered in 2009, the Daily Mail reported.
In 2008, parts of three other skeletons were found in the world-famous Cradle of Humankind site north of Johannesburg.
Scientists are not sure whether the species, which had long arms, a small brain and a thumb possibly used for precision gripping, was a direct ancestor of humans' genus, Homo, or simply it's close relative.
"It appears that we now have some of the most critical and complete remains of the skeleton," Berger said.
The skeleton, which has been dubbed Karabo, would have been aged between nine and 13 years when the upright-walking tree climber died.
The sediba fossils are arguably the most complete remains of any hominids found and are possibly one of the most significant paleoanthropological discoveries in recent time.
The Cradle of Humankind, now a World Heritage Site, is the oldest continuous paleontologies dig in the world.
The university also announced it would open up the process of exploring and uncovering fossil remains to the public and stream it on-line in real time.
"The public will be able to participate fully in live science and future discoveries as they occur in real time -an unprecedented moment in paleoanthropology," said Berger.