An article published in “The Journal of the Geological Society” describes a research on fossils dating back to about 600 million years ago found in the Chinese site of Weng’an. A team of researchers led by the British University of Bristol believes that those might not be some of the oldest remains of animals ever found but algae.
In the Weng’an area there’s the Doushantuo Formation, characterized by sedimentary rocks that contain an abundant amount of fossils in excellent state of conservation. In its layers microfossils have been found with an age ranging from 550 to 635 million years ago in the Ediacaran, a geological period in many ways still mysterious. They’re the source of many discussions about the interpretation of organisms that lived at that time, which are really unique and are therefore difficult to reconstruct completely from a few fossils.
Among the many fossils found in the Doushantuo Formation there are acritarchs, which form a very diverse group of microfossils. Most likely these are eukaryotic organisms, meaning that they’re composed of complex cells such as animals, plants and fungi, but their classification is very vague at the moment, so much that they form a heterogeneous group into which microfossils not yet well identified are added.
The positive news is that well-preserved microfossils have been found in the Doushantuo Formation that allow the identification of subcellular structures, including possible cell nuclei. This is a type of identification possible thanks to sophisticated tomographic analyzes but those are the only information available to try to figure out whether those are animals or other types of organisms. That’s because they are not recognizable as remains of adult animals but only as single cells or groups of cells that may be embryos or other organism parts.
Various researchers pointed out some cellular features of the fossils discovered in Weng’an as a clue to their animal nature. However, these are features common also to other groups of multicellular organisms, including algae. In the absence of elements that can prove their nature, it’s impossible to assign them to a specific group.
This new research offers more questions than answers by showing the ambiguity of the characteristics of the Weng’an organisms. It’s yet another demonstration of the difficulties paleontologists are encountering in understanding the nature of the organisms of the Ediacaran period, so different not only from the ones living today but also from those that evolved in the following periods.
Another problem in Weng’an is that mining operations are becoming more intense. The phosphate digging for the production of fertilizers could lead to the destruction of the rocks containing these microfossils that are precious to understand a period of evolution of life on Earth that’s still mysterious in many ways.