Ancient fossils: Plants or animals?

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BLACKSBURG, Va., Feb. 21 (UPI) -- U.S. scientists say mysterious ancient fossils discovered in China defy classification, puzzling researchers who can't decide if they're plant or animal.

Either way, they say, the fossils could shed new light on the evolution of large, complex organisms and indicate they may have diversified earlier than thought, LiveScience.com reported.

The researchers say the fossils, found in China's southern Anhui province, date to between 580 million and 635 million years ago.

Two of the fossil organisms resemble seaweed, while three other new types are difficult to classify as animal or plant.

"Some of my colleagues are more leaning toward the animal interpretation," said study researcher Shuhai Xiao, a professor of geobiology at Virginia Polytechnic Institute and State University. "But my personal view is that we still don't know what they are."

These fossils date to the first part of the Ediacaran Period, the time when life became big, or at least visible to the naked eye, scientists say.

"Animals in the Ediacaran Period are almost universally bizarre, and it is very difficult to place them in any modern animal phyla," Xiao said. "They may be precursors to modern animals or offshoots of modern animals that don't have any direct descendants."