The first skull of the earliest known ancestor of the giant panda has 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.

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The animal, formally known as Ailuropoda microta, or "pygmy giant panda," would have been about 3 feet long, compared to the modern giant panda, which averages in excess of 5 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 schuh-HON.

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