Non-mineralized microbial pseudofossils in Gaojiashan biota: A new understanding of the preservation of organisms soft bodies in the latest Ediacaran

The Ediacaran Gaojiashan biota from the Dengying Formation in Lijiagou section in the southern Shaanxi Province contains a large number of phosphatized fossils, including abundant tubular fossils, vase-shaped fossils and calcified cyanobacteria. With the deepening of research, microbial pseudofossils are recovered in the biota. The structure and even the whole body were duplicated by aggregated spherical or filamentous cyanobacteria through direct replacement of microorganisms. Microorganisms can enrich and accumulate phosphate rapidly by changing the physical and chemical conditions in the environment, which plays an important role in the preservation of non-mineral tissues including soft bodies of organisms. According to the degree of substitution, they can be divided into complete substituting and incomplete substituting types. Soft bodies or possible embryonic morphological characteristics were completely duplicated by microorganisms through casting moulds. This discovery provides another way for the preservation of non-mineralized biological tissues in Gaojiashan biota and a new understanding of the preservation of organisms soft bodies in this period.