Chengjiang creature oryctocoenose is located in the Maotian Mountain of Chengjiang in Yuxi City, Yunnan Province. There are many fossil remains of more than 80 species of creatures such as Yunnan worms, Fuxian Lake worms, Maotian Mountain worms, trilobite and medusa, etc. It is the most ancient mollusk oryctocoenose preserved in perfect condition, in which the species of mollusk account for 90% or more.     

The discovery of medusa fossils in Chengjiang creature oryctocoenose filled up the gap in ancient bioresearch of China. It is also the first time for international bioresearch circle to find fossils of the pre-Cambrian period. Yunnan worm, found in the oryctocoenose, was the most ancient chordate, which is an astonishing discovery in the international bioresearch. According to the researches, Yunnan worm had a body length of 3 cm to 5 cm, with black color. Inhabiting in water, it swam in wave curves generated by contraction of body muscles. Though ugly in appearance, it was not only the ancestor of all reptiles and mammals including human being, but also the "pioneer inhabitant" on earth.

Generally, after the long geological evolution, only the bones of creatures can be fossilized while the flesh is hardly preserved. However, the specific environment of Chengjiang River enables the mollusk to be turned into fossils, which is a mystery in science.

It takes 1 million to 3 million years for Chengjiang creature oryctocoenose to form. In such a short geologic period, the paroxysmal evolutionary process of animal population was completely recorded, revealing the "Big Bang of Creatures" in the Cambrian period. Scientists regard Chengjiang creature oryctocoenose as one of the world-class scientific discoveries in the 20^th century, which is an unparalleled golden key to uncover the secret of "Big Bang of Creatures" happened in the Cambrian period.