Half the species in a new Cambrian fossil site are completely new to us

Enlarge / The level of detail in some of the fossils is astonishing. (credit: Dongjing Fu et. al.)

The first signs of complex animal life begin in the Ediacaran Period, which started more than 600 million years ago. But it's difficult to understand how those organisms relate to the life we see around us today. Part of this issue is that those fossils are rare, as many rocks of that period appear to have been wiped off the Earth by a globe-spanning glaciation. But another problem is that the organisms we do see from this period aren't clearly related to anything that came after them.

With the arrival of the Cambrian Period about 550 million years ago, all of that changed. In fossil beds like the famed Burgess Shale, we can see organisms that clearly have features of the major groups of life that have persisted to this day. As more collections of fossils become available, we can even watch groups diversify as the Cambrian progressed. But there's still considerable debate over whether these changes represent a true, multi-million-year "explosion" and what environmental changes might have driven this diversification.

We may be on the verge of some big help in answering these questions, as scientists are announcing the discovery of a spectacular deposit of Cambrian fossils from South China. The fossils include dozens of species, half of which we've never seen before, and appear to represent a previously upsampled ecological zone. The preservation is such that soft-bodied creatures like jellyfish, and the softer body parts of creatures with shells, can easily be made out in the rocks. Best yet, the researchers who uncovered the samples suggest that rocks from the same formation are widespread in China.