Research On Experimental Taphonomy Of Phosphatized Embryo Fossils

The globe-scaled phosphorite-formation events in Ediacaran Period and Early Cambrian have resulted in the wide spread of phosphate rocks all over the world. In particular, a great deal of embryo fossils were found in the Doushantuo Formation of the Ediacaran Period and Meishucun stage of Early Cambrian. Due to the phosphatization, delicate and fine structures of those embryo fossils were preserved. The embryo fossils have not only provided a lot of precious information for explaining the development patterns, origins and evolutions of early animals but also made it possible to verify hypotheses on developmental biology and evolutionary embryology. Currently, however, little is known about the formation mechanism and preservation potential of embryo fossils through phosphatization, furthermore, the probabilities of fossils be kept to become fossils in separate stages need to be studied. This paper, through conducting a series of experimental taphonomy with regard to the above-mentioned aspects, is trying to find the answers.So far, among the discovered phosphatized embryo fossils in the Ediacaran Doushantuo Formation, no blastula stage specimens has been identified. In general, there are three explanations for such phenomenon: first, they are embryos of lower animals and their cleavages ended before the blastula stage; second, gastrula stage was absent in the process of embryonic development of multicellular animals in that geological history and the animals become developed directly from parenchymula development; third, The fidelity was difficult to preserve in the embryos and larvae with high degrees of division due to certain factors, such as their chemical compositions and buried environment, etc.The above two hypotheses need to be verified by more fossil evidences in future. This experiment is aiming at studying the preservation potential of embryo development in different stages through simulating the environment saturated with phosphores and verifying the correctness of the third hypothesis through controlling the experiment. Conditions applied by the experiment can be realized in the natural environment and also were widely exist in the geological history. Through experimentally simulating the process of embryo phosphatization, this paper is also trying to reconstruction the environment and timing of phosphatization, and conduct some exploratory studies on the mechanism of embryo phosphatization.