The Khesen Formation microfossils offer new clues about the appearance of the first animals

Some microfossils from the Khesen Formation (Image courtesy Yale University)
Some microfossils from the Khesen Formation (Image courtesy Yale University)

An article published in the journal “Geology” describes a research on microfossils in excellent state of conservation discovered in northern Mongolia that could help to understand the evolution from microbes to animals. A team of researchers led by the Yale University studied these embryo-like fossils discovered in what was called Khesen Formation dating to about 540 million years ago, during the Ediacaran period.

The discovery of the Khesen Formation has been defined as the most significant regarding early animal fossils after the Doushantuo Formation at the Chinese site of Weng’an, characterized by sedimentary rocks that contain an abundant amount of fossils in excellent state of preservation and even older, even more than 600 million years.

The strange characteristics of the fossils of the Doushantuo Formation have been the subject of discussions for the past two decades in the field of paleontology for the difficulty of classifying them. For example, an article published in May 2017 in “Journal of the Geological Society” described a research on some of them hypothesizing that they were algae and not animals. That’s an important issue because it concerns the research on the origin of animals.

In the field of paleontology, the discovery of new fossils can make a difference in research concerning a certain group of organisms, in this case in particular the appearance of the first animals. In general, it can help to better understand the organisms that lived in the Ediacaran period and the transition with the Cambrian period.

Among the organisms found also in the Khesen formation there are acritarchs, which form a group of very diverse microfossils and, again, with problems in classifying the various specimens. According to the researchers, the microfossils examined contain a total of 17 species of organisms belonging to 8 taxonomic genera, of which only one part consists of acritarchs.

The researchers identified the Appendisphaera, Cavaspina and Variomargosphaeridium taxa and the possible alga Archaeophycus yunnanensis. There are also organisms attributed to the Megasphaera genus, classified as bacteria but also at the center of discussions. Ross Anderson, the first author of this study, explained that this is just the tip of an iceberg because most of the fossils come from two only samples.

The Khesen formation was considered interesting since the beginning for the presence of phosphorites, sedimentary rocks with a high phosphate content. Rocks of that kind preserved similar organisms in China so the researchers had good hopes of discovering some interesting fossils. The results already arrived from the first exams and there are expectations for the new ones that will be conducted in the future.

In essence, this study is just the beginning of a research campaign on the fossils of the Khesen Formation, which already showed a very interesting potential. The team led by the Yale University has already conducted more work to get more samples in different areas of the Khesen Formation.

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