Palaeontologist, Dr. Michael Archer, has been suspecting if it were not for the satellite technology, he would have been on an isolated outcrop only in north-west Queensland.

While an untrained eye would see a baseball-sized rock carried by the palaeontologist as congealed dirt, experts believe that the same had hints to an essential time, though unknown, in the history of the continent.

It has been found that flecks of white bone could barely be seen on the surface of the rock. These have, however, been identified by a group of scientists as the teeth and limbs of many distinct primitive mammal groups. These first had been discovered in the fossil record back over 20 million years.

The rock is being studied by Michael Archer and his colleagues from the University of NSW by searching through the dust and dirt of Riversleigh. Piles of silt-covered rocks have been extracted by them from a small pit that was unveiled last year next to the Riversleigh World Heritage fossil site.

"While the known fossil deposits span environmental change over the last 25 million years, there are some `holes' in the record including the period about 13 to 5 million years ago", Professor Archer was cited as saying.