Abstract:Discoid fossils are the earliest and the most important components in the Ediacaran biota, which were crucial for the rebuilding of the ecosystem during the Ediacaran–Cambrian transition and for the understanding of the early evolution of organisms during the "Cambrian Explosion of life". Aspidella, a disk-like Ediacaran form genus, is a typical fossil in Ediacaran sediments distributed worldwide. This article describes the Ediacaran biota element Aspidella disc-like fossil (cf. Aspidella) which is here first recorded in siliceous rocks at the bottom of the Taozichong Formation of the Ediacaran–Cambrian transitional strata in Qingzhen of Guizhou as a disc characterized by concentric ring, central bulge and indentation. A 3D image of the Aspidella fossil shows obvious step-like layer changes. We tend to think that cf. Aspidella of Taozichong Formation is the holdfast of benthic soft-body phylloids, and its internal sediments are formed by normal sedimentation of seawater. Fragments of holdfast biofilm containing Fe and Al substances have been found. It is confirmed that the holdfast was preferentially preserved by a microbial mat, while the stem and compound leaves disappeared, and differential compaction of clay and sand produced a stepped profile on the bulb wall of the holdfast after death. Based on the similarity between the bioassemblages in the Ediacaran–Cambrian Taozichong Formation of South China and the Ediacaran in the North China and Qaidam blocks, and the global paleogeographic pattern during the transition period from Ediacaran to Cambrian, the South China Plate have moved continuously from the middle latitudes to the low latitudes of the North China and Qaidam blocks. Environmental changes may have induced the population continuation of late Ediacaran biota elements in the South China Cambrian strata, and further expanding the temporal and spatial distribution of classic Ediacaran-type fossils in geological history.
