The trace-fossil record of the Cambrian explosion

寒武纪大爆发代表了生命史上最戏剧性的一幕。在埃迪卡拉纪（生物群以软体生物为主）之后，化石记录发生了迅速的变化，寒武纪下岩石中出现了几乎所有基本动物身体形态的化石代表。关于动物的早期进化有两种相反的观点。一种观点认为，化石记录的表面价值有利于现代门的快速起源（寒武纪大爆发）。另一种观点强调化石记录的不完美本质，强调在后生动物进化史中有深层前寒武纪根源的概念。根据第二种观点，在显生宙开始时突然出现的化石只是一种人工产物，这是由于矿物化骨骼的获取增加了人体化石的可保存性。技术包括对生物成因结构（被称为微量化石）的研究，这些结构是由生物与基质之间的相互作用产生的。因为痕迹化石通常是由软体动物产生的，所以它们不像身体化石那样受到保存的限制。因此，痕量化石可能为校准寒武纪大爆发提供一条独立的证据线。本项目的目标是：(1)记录与寒武纪大爆发及其福图尼期前哨有关的水生动物；(2)在生物圈历史的关键时刻，探索化石遗迹的潜力，以提高我们对寒武纪生态系统建设的认识；(3)探索技术信息如何提供对这一突破的时间和环境限制的见解，揭示进化创新的潜在历时性。******

The Cambrian explosion represents one of the most dramatic episodes in the history of life. Following a period known as Ediacaran, when biotas were dominated by soft-bodied*organisms, the fossil record changed rapidly as revealed by the appearance of fossilized representatives of almost all the basic animal body plans in lower Cambrian rocks. There are two opposed views on the early evolution of animals. One view considers the fossil record at face value, favoring a scenario of rapid origination of modern phyla (the Cambrian explosion). The other view stresses the imperfect nature of the fossil record, stressing the notion of deep Precambrian roots in metazoan evolutionary history. According to this*second perspective, the sudden appearance of fossils near the beginning of the Phanerozoic is just an artifact resulting from an increase in preservability of body fossils related to the acquisition of mineralized skeletons. Ichnology comprises the study of biogenic structures (known as trace fossils) that result from the interactions between organisms and the substrate. Because trace fossils are commonly produced by soft-bodied animals, they are not subjected to the same preservational constrains than body fossils. Accordingly, trace fossils may offer an independent line of evidence to calibrate the Cambrian explosion. The objectives of this project are: (1) to document ichnofaunas associated with the*Cambrian explosion and its Fortunian prelude, (2) to explore the potential of trace fossils to improve our understanding of Cambrian ecosystem construction at a critical time in the history of the biosphere; and (3) to explore how ichnologic information provides insights into the timing and environmental constrains of this breaktrough, revealing potential diachronism in evolutionary innovations.******