Tiny fossils spotted in southwest China's Yunnan-Guizhou Plateau indicate the earliest complex animal species were possibly born in China and appeared on the surface of the Earth about 580 million years ago, much earlier than had been thought.

The latest issue of Scientific American this month carries an article about the significance of the tiny, button-shaped organism dating back 580 million years ago, which was believed to be the oldest animal species with symmetrical structure.

Unearthed from Chinese phosphate mines, these species provide the most ancient evidence of animal species complex enough to have a symmetrical two-sided body plan, just like flies, fish and humans in the modern world, instead of a round or radial one. 

"They date back to the time prior to the Cambrian Period at least 40 million years ago, when the fossils recorded a big bang of life," said Chen Junyuan, a noted paleontologist with the Nanjing Institute of Geology and Paleontology in China.

"The delicately preserved fossils indicated the dawn for the world of diversified living species," Chen acknowledged. Before the Cambrian Period 550 million years ago, most life on Earth took the form of bacteria and single-celled species.

The exact timing of the emergence of bilateral animal species, which have defined front, rear, left and right body surfaces, has long been a topic of debate in the present scientific community.

Working along with an expert team from overseas, Chen named the new living species Vernanimalcula guizhouena, meaning "small spring animal from Guizhou" -- a nod by the team to the "spring" following the so-called "Snowball Earth" period that ended roughly 600 million years ago when it was theorized that most of the planet was entombed in ice.

Chen and his peers described 10 bilateral fossils they spotted and collected from the Doushantuo Formation in China, which constitutes a phosphorite rock formation that developed in a shallow sea anywhere from 580 to 600 million years ago.

The oval Vernanimalcula guizhouena was about 0.2 millimeters, equivalent to the size of two to four human hairs laid side by side.

These soft bodies were kept intact due to the phosphate, which, thanks to very special conditions, quickly worked its way into the cellular structures.

Some scientists also held that there were lower bilateral animal species form before Vernanimalcula guizhouena.

The planet had been rigid cold, about 30 degrees Celsius below zero, for tens of millions of years before Vernanimalcula guizhouena came into being and that's extremely unfit for life, said Prof. Chia-Wei Li, a paleontologist with Taiwan Tsinghua University.

This lays down a milestone in the study of early life forms and many paleontologists have dreamed of achieving such findings, said Derek E. G. Briggs of Yale Institute for Biospheric Studies.

The finding of Vernanimalcula guizhouena represented a pioneering job and raised scientists' horizon to explore the early life on the Earth, said Derek E. G. Briggs, a paleontologist with Berlin Technical University in Germany.

(Xinhua News Agency August 26, 2005)