Chengjiang Fossil Site, Fossil site and UNESCO World Heritage Site in Chengjiang, Yunnan, China

The Chengjiang Fossil Site covers 512 hectares of Maotianshan hill and nearby outcrops in Chengjiang City, Yunnan. Its Heilinpu Formation, specifically the Maotianshan Shale Member, preserves early Cambrian marine fossils about 518 million years old. The beds have yielded 16 phyla and nearly 300 species, including the oldest known vertebrate, Myllokunmingia.

The site was discovered in 1984 by a Chinese geologist and revealed a wide range of animal life from the early phase of animal development known as the Cambrian explosion. The find shifted how scientists understood the speed at which complex organisms appeared on Earth.

The name Maotianshan, "Cat Heaven Hill", refers to the hill above the fossil beds and has no link to the fossils themselves. The site's fossil assemblage is called the Chengjiang biota, and the 2012 World Heritage listing covers 512 hectares. Finds include the oldest known vertebrate, Myllokunmingia, described in 1999.

The site is located outside Chengjiang City, and joining a guided tour from Kunming is a comfortable way to get there. On-site panels and a museum help make sense of the ancient layers and orient you around the grounds.

Many of the fossils found here still contain soft body parts and even internal organs, which is extremely rare in rocks of this age. This level of preservation allows researchers to study the exact body structure of animals that lived over half a billion years ago.