Abstract
In traditional geology, Cambrian was thought to be the first era that life evolved from single cell to multicellular organisms. Through discovery of pre-Cambrian metazoan fossils and calibration in molecular evolution, the original time of metazoans is gradually pushed back to an earlier age. Still, the Cambrian fossils are the first choice for studying the early metazoan evolution and their biomineralization.From the 1980’s, Chengjiang faunas became a very important material to study the biosphere of Cambrian. In this area, fossils were perfectly preserved, so it gave the researchers enough information to understand the biosphere and morphology. At the same time, because the stratum of Chengjiang and other Cambrian strata have great differences in the element composition, we could neglect the effects of the stratum and find out the original structure.Here, we choose the plates of Microdictyon and the sclerites of Chancelloriids both found in Chengjiang, Yunnan and Zhenba, Shaanxi as the main object of study, and try to understand their original structure and the processes of fossilization by comparing the element composition of fossils from different area. We find that the structure of Microdictyon plates is a regular silicate framework, with a phosphate capping which was thought as originally mineralized previously, and a layer of organic carbon around the edge. The sclerites of Chancellariids have a calcareous wall, filling with phosphate, and toughing some organic carbon on their surface.To sum up, we consider that the processes of fossilization in Chengjiang must be unique. It could preserve the soft tissue very well and help us to find out their original structure and know the early metazoan evolution.Abstract ii總目錄 iii第一章、 前言 11. 生命的起源與寒武紀大爆發 12. 生物礦化概論 23. 寒武紀時的生物礦化 44. 微網蟲概論 45. 開腔骨概論 66. 研究目的 7第二章、 材料來源及研究方法 91. 澄江地區的古生物 9i. 岩塊的來源 9ii. 樣品之前處理 9iii. 掃瞄式電子顯微鏡及電子能譜分析 92. 鎮巴地區的古生物 9i. 岩塊的來源 9ii. 岩塊及古生物的分離 10iii. 樣品之前處理 10iv. 掃瞄式電子顯微鏡及電子能譜分析 10v. 穿透式電子顯微鏡 10第三章、 實驗結果 111. 澄江微網蟲骨片在掃瞄式電子顯微鏡下的觀察結果 112. 鎮巴微網蟲骨片在掃瞄式電子顯微鏡下的觀察結果 113. 澄江開腔骨腔骨在掃瞄式電子顯微鏡下的觀察結果 114. 鎮巴開腔骨腔骨在掃瞄式電子顯微鏡下的觀察結果 125. 鎮巴微網蟲骨片在穿透式電子顯微鏡下的觀察結果 12第四章、 討論 131. 微網蟲骨片的礦化結構 132. 開腔骨腔骨的礦化結構 153. 下寒武紀時的生物礦化 164. 結論 17參考文獻 19圖目錄 21