Chengjiang biota

The Chengjiang biota is a collection of fossils about 518 million years old from the Maotianshan Shale near Chengjiang in Yunnan Province, southwest China. Hou Xianguang of the Nanjing Institute of Geology and Palaeontology found the first specimens in 1984. Over the years Chinese teams, including Chen Junyuan and Shu Degan, have found well over 250 species, from arthropods and worms to sponges and animals with no living relatives. UNESCO made the site a World Heritage Site in 2012.¹²

Fine silt buried animals during storms or sudden mud flows in an oxygen-poor sea floor, which slowed decay. The mudstone then preserved the guts, eyes and nerves of animals such as Fuxianhuia, a shrimp-like arthropod, and Leanchoilia with its grasping appendages. Chengjiang is about 10 million years older than the Burgess Shale and shows that the main animal body plans were already established early in the Cambrian.¹

The most famous fossils are Myllokunmingia and Haikouichthys, small fish-like animals with gill pouches, a head and muscle blocks, that are among the earliest vertebrates known. Predators like Lyrarapax, a relative of Anomalocaris, hunted among sponges, worms and arthropods. Chengjiang made it plain that the Cambrian Explosion was a real diversification of animals, not an artefact of poor older records, and it gave scientists a view of soft anatomy, such as guts and nerves, that sites with only shells and bones rarely allow.¹²