Ediacara Fossils Preserved in Ediacaran Bituminous Limestone

摘要：埃迪卡拉化石代表了埃迪卡拉晚期（约5.8 - 5.4亿年前）最早、最复杂的大型生物。它们于1872年首次在纽芬兰被发现，后来在纳米比亚、澳大利亚、俄罗斯、西伯利亚、英国、北美和华南被发现。尽管埃迪卡拉化石对于理解宏观生命的早期进化具有重要意义，其广泛的地理分布和长期以来成为科学研究的目标，但它们的形态、古生态和系统发育解释尚未完全解决。一个关键的挑战与大多数埃迪卡拉化石的保存方式有关：几乎所有的埃迪卡拉化石都是在砂岩或粉砂岩中以铸件和模具的形式保存的，这使得重建形态变得困难。本项目旨在研究中国南方长江三峡地区灯影组（5.51 - 5.42亿年前）沥青灰岩中保存罕见的埃迪卡拉组合。初步调查发现了至少五种新的埃迪卡拉虫。这些化石似乎是在三维空间和原位保存下来的。其中一些显示出降解的有机壁遗迹，形态重建表明它们平卧在水-沉积物界面或其附近。本项目的近期目标是对长江三峡地区灯影组进行系统的野外调查和采集，并利用系列薄切片、光镜、扫描电镜和电子探针技术对灯影埃迪卡拉化石进行细致的研究。本研究的长期目标是解决与灯影埃迪卡拉组合的生物多样性、体形、地学和古生态学有关的问题。因此，这项研究的科学意义在于提高我们对最早的复杂大型生物——埃迪卡拉动物群进化的认识。

Ediacara Fossils Preserved in Ediacaran Bituminous LimestoneShuhai Xiao, Virginia Polytechnic Institute and State UniversityEAR-0545135AbstractEdiacara fossils represent some of the earliest, complex macroorganisms in the late Ediacaran Period (approximately 580-540 million years ago). They were first discovered in Newfoundland in 1872, and have later been found in Namibia, Australia, Russia, Siberia, England, North America, and South China. Despite their importance in understanding the early evolution of macroscopic life, their wide geographic distribution, and their long history of being targeted for scientific investigation, the morphological, paleoecological, and phylogenetic interpretation of Ediacara fossils has not been completely resolved. A key challenge has to do with the way most Ediacara fossils are preserved: almost all Ediacara fossils are preserved as casts and molds in sandstone or siltstone, making it difficult to reconstruct the morphologies.This project is designed to study an unusually preserved Ediacara assemblage from bituminous limestone of the Dengying Formation (551-542 million years ago) in the Yangtze Gorges area of South China. Preliminary investigation has recovered at least five new Ediacara forms. The fossils appear to have been preserved in three dimensions and in situ. Some of them show remains of degraded organic walls, and morphological reconstruction indicates that they lived procumbently at or near the water-sediment interface. The immediate objective of this project is to carry out systematic field investigation and collection of the Dengying Formation in the Yangtze Gorges area, and to carefully study the Dengying Ediacara fossils using serial thin section, light microscopy, SEM, and electron microprobe techniques. The long-term goal of this research is to address questions related to the biodiversity, bodyplan, taphonomy, and paleoecology of the Dengying Ediacara assemblage. Thus, the scientific significance of this research is to advance our knowledge about the evolution of the earliest complex macroorganisms - the Ediacaran biota.