NANJING, July 8 (Xinhua) -- Using advanced experimental techniques, Chinese paleontologists have confirmed that the yunnanozoans, mysterious fishlike forms which lived 518 million years ago, were the oldest vertebrates on earth.

The Chengjiang fauna, a Cambrian fossil site in southwest China's Yunnan Province, has retained a large number of ancestral groups of vertebrates, and scientists have been expecting to solve the mystery of the origin of vertebrates from it.

Researchers from the Nanjing Institute of Geology and Palaeontology under the Chinese Academy of Sciences have examined specimens of yunnanozoans from the Chengjiang fauna using previously unexplored techniques such as x-ray microtomography, scanning and transmission electron microscopy, and energy dispersive spectrometry element mapping.

They found evidence that yunnanozoans branchial arches consist of cellular cartilage with an extracellular matrix dominated by microfibrils, a feature considered specific to vertebrates.

"Many primitive features of yunnanozoans may provide key insights of evolution that could unravel the mystery of where vertebrates came from," said Zhao Fangchen, a researcher with the institute.

The research findings were published in Science magazine on Friday.