Scientists at the Virginia Institute of Technology found that the first mass extinction in the history of the Earth occurred approximately 550 million years ago due to a decrease in the level of oxygen dissolved in water. Writes about it “Lenta.ru” citing an article in Proceedings of the National Academy of Sciences (PNAS).
It is specified that the first known mass extinction occurred at the end of the Ediacaran period. The Ediacaran biota are the most ancient complex organisms that lived approximately 635-542 million years ago. The biota consists of three complexes different in time – Avalonsky, Belomorsky and Nama. Each has its own generic diversity, but it is significantly reduced from the Belomorsky complex to Nama. Scientists suggest that this is due to the mass extinction, but its causes are still unclear.
The researchers analyzed a number of fossils of the Ediacaran biota to calculate the parameters of the environments in which ancient animals lived and under what conditions they were buried. It turned out that about 80% of the animals that existed at the time of the Belomorsky complex were absent from the Nama complex. The scientists noted that sampling bias is excluded, since the representation of sampling sites and depositional conditions between the complexes are similar to each other. There are minimal ecological differences between the Belomorian complex and the Nama complex; therefore, the option of replacing one biota with another is impossible.
Disappeared taxa are characterized by a variety of behavioral and morphological features, this does not refute the model of mass extinction. At that time, those species of animals survived, whose feature was a large body area in relation to volume. This confirms the theory that the global availability of oxygen in the ocean is decreasing.