Their work is reported in the October 27 issue of Science. It was thought they became extinct before the end of the Precambrian period. This new evidence leaves open the possibility that Ediacarans played a role in the development of the multitude of flora and fauna that characterize the Cambrian period and which are the predecessors of the life on Earth today. The dating was done on grains of the mineral zircon found in the Namibian volcanic ash. Zircon occurs in trace quantities in some volcanic rocks.
Zircons allow uranium into their crystal structure and over time the uranium decays to lead.
This technique allows dating of rocks that are 500 million years old to an accuracy of better than plus or minus 1 million years. The more precisely we can resolve time the more sophisticated the evolutionary questions we can address. Rock and fossil records provide relative ages.