WASHINGTON - The first skull of the earliest known ancestor of the giant panda was been discovered in China, researchers report.

Discovery of the skull, estimated to be at least 2 million years old, is reported by Russell L. Ciochon in Tuesday's edition of Proceedings of the National Academy of Sciences.

Ciochon, an anthropologist at the University of Iowa, and a team of U.S. and Chinese researchers, made the find in a limestone cave in south China.

The animal, formally known as Ailuropoda microta, or "pygmy giant panda," would have been about three feet long, compared to the modern giant panda, which averages in excess of five feet.

Previously this animal had been known only by a few teeth and bones, but a skull had never been found.

Judging by the wear patterns on its teeth it also lived on a diet of bamboo, the main food of the current giant panda, the researchers said.

Other than size, the animal was anatomically similar to today's giant panda, said Ciochon, pronounced, pronounced schuh-HON.

The work was funded by the Chinese National Natural Science Foundation and University of Iowa.