Samples of the fossilized fish, dating back 530 million years, were first found in 1997 at Haikou, near Kunming, capital of southwest China's Yunnan Province.

The findings were made by Chinese palaeontologist Shu Degan in partnership with scholars from Britain, France and Japan.

The latest edition of British-based Nature magazine carries an article depicting the structural features of the head and backbone of haikouichthy, which are acknowledged as evidence that the fish was the most ancient vertebrate.

The prestigious scientific weekly has carried seven articles on serial research findings by Professor Shu and other palaeontologists on deuterostome in the "Cambrian Life Explosion."

The earth's fauna were divided into two large groups, vertebrates and invertebrates, by scientists some 200 years ago and zoologists have been trying to discover the evolutionary relationship between the two, Professor Shu Degan says.

Many hypotheses have been raised by zoologists and molecular biologists, which have contradicted each other. For years direct proof from authentic fossils for the origin of vertebrates has been wanting.

"To pinpoint vertebrates' origin in positive palaeontological research, the primary work is to search for fossilized remains of the most primitive vertebrates," says Professor Shu, who works with the Northwest University, based in northwest China's Shaanxi Province.

In 1999, a group of Chinese scholars, including Shu, also discovered fossils of the Haikou fish in the Lower Cambrian stratum of 530 million years ago at the Chengjiang Fossil Fauna in Yunnan Province.

The discovery, hailed by Nature as "catching the first fish," helped move back the history of the most primitive vertebrates another 50 million years.

However, initial reports on the conclusion was based on only two specimens which bore limited anatomical information, especially crucial information about the heads and backbones of common vertebrates. This made it impossible to determine the fish's position in evolutionary history.

Fortunately, hundreds of specimens of Haikou fish were found recently by the Research Institute of Earlier Life in the Northwest University, providing a great deal of significant biological information, including head and backbone structures.

Development of the reproductive organ of the Haikou fish was far behind that of its non-reproductive organ, according to Professor Shu. This unique structural feature of Haikou fish, the most primitive vertebrate, probably provides clues for the crucial intermediate species in the process of vertebrates evolving from invertebrates, for which scientists in evolution have for long waited, Shu says.

Analytical findings of existing fish and fossilized lower fishes also show the Haikou fish is the most primitive vertebrate known and that southern China is probably the "root" of the whole evolutionary tree of vertebrates, the professor says.

(China Daily January 31, 2003)