Many strange new creatures are discovered in China

ONE OF the core tenets of fossilisation is that hard material preserves more readily than the soft stuff. This fact has made studying the evolution of the first animals 540m years ago a bit of a problem since the vast majority (with the notable exception of trilobites) lacked hard body parts. So far, only a handful of fossil sites that formed in unusual ways have allowed palaeontologists to glimpse what ancient ecosystems were like without all soft-bodied organisms being filtered out of the equation. Now another new site has been added to the list. This week Xingliang Zhang of Northwest University in China reports in Science the discovery of a new site full of animals that have never been seen before.Most fossils form when sediment in water slowly rains down upon the body of a dead animal. Soft tissue rots away but hard bits (like bone) get entombed and protected inside the sedimentary rock that forms around them. For soft-bodied animals to be preserved, something catastrophic must take place. In the case of the world’s two most famous Cambrian sites, the Burgess Shale accumulation in Canada and the Chengjiang site in China, this catastrophe was a series of storms that dumped vast quantities of mud upon a community of animals, burying them alive. Much animal flesh still rotted away but traces of their soft bodies were preserved as organic films in the anoxic mud hardened around them.