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Chengjiang fossils (China)
c. 518 million years ago (found 1984)· Fossil or site· Animals
Well establishedStrong fossil, genetic or geological evidence.
A trove of 518-million-year-old fossils in Yunnan, China, preserving soft-bodied animals from early in the Cambrian explosion.
See it on the Life map →What happened
In 1984 paleontologist Hou Xianguang split a mudstone slab near Chengjiang, Yunnan province, and found a complete soft-bodied arthropod. The site has since yielded more than 250 species, many with guts, eyes, gills and even traces of nerves preserved as thin films. Sudden mudflows buried animals in oxygen-poor water, slowing decay. Finds include early arthropods, worms, sponges, radiodont predators and the first known vertebrates.
Why it matters
It shows the Cambrian explosion was well under way by 518 million years ago, about 10 million years before the Burgess Shale, and reveals early animal anatomy in detail.
The evidence (fossils, genes, rocks)
Tens of thousands of specimens collected since 1984, dated by uranium-lead ages from volcanic ash layers; a UNESCO World Heritage Site since 2012.
Still debated
How soft organs such as brains survived is still studied, and some claimed nerve and brain traces are disputed as possible decay or mineral artifacts.
Connections (2)
▸Chengjiang fossils (China) preserve First vertebrates: jawless fishWell established
The connection
Chengjiang's fine mud and rapid burial preserved soft tissues that normally rot, including the cartilage, gill pouches and muscle blocks of the earliest fish. Without this rare preservation, the first jawless vertebrates, which had no bone or teeth, would probably be invisible in the fossil record.
When and how
Near Haikou and Chengjiang, Yunnan province, China, about 518 million years ago; Haikouichthys and Myllokunmingia were described by Shu Degan and colleagues in 1999.
The evidence
Over 500 specimens described in 2003 show consistent vertebrate features: eyes, gill arches, zigzag muscle blocks and simple backbone elements.
Debates and open questions
Whether these animals are full vertebrates or close relatives just outside the group, and whether some features are artifacts of decay.
▸Chengjiang fossils (China) are an older counterpart of Burgess Shale (Canada)Well established
The connection
Both sites record the Cambrian explosion through the same rare soft-tissue preservation. Chengjiang is about 10 million years older and on a different continent, yet shares many kinds of animal, such as radiodonts, lobopodians and early chordates. Together they show that these communities were widespread and lasted for millions of years.
When and how
Chengjiang, Yunnan, China (about 518 million years ago, found 1984) and the Burgess Shale, British Columbia, Canada (about 508 million years ago, found 1909).
The evidence
Shared genera and close relatives at both sites, with dates from volcanic ash at Chengjiang and from fossil zones at the Burgess Shale.
Debates and open questions
How much the differences between the sites reflect time, geography or local setting, and why such preservation was common in the Cambrian but rare afterward.