The trace-fossil record of the Cambrian explosion

寒武纪大爆发是生命史上最具戏剧性的事件之一。在埃迪卡拉纪（Ediacaran）之后，生物化石主要是软体生物，化石记录发生了迅速的变化，下寒武纪岩石中出现了几乎所有基本动物体型的化石代表。关于动物的早期进化有两种对立的观点。有一种观点认为化石记录只是表面价值，倾向于现代门快速起源（寒武纪大爆发）。另一种观点强调化石记录的不完美性，强调后生动物进化历史中前寒武纪的深层根源。根据第二种观点，在中生代开始时突然出现的化石只是一种人为的产物，这是由于与矿化骨骼的获得有关的身体化石的可重复性增加而产生的。遗迹学包括对生物和基质之间相互作用产生的生物结构（称为遗迹化石）的研究。由于遗迹化石通常是由软体动物产生的，它们不像身体化石那样受到同样的限制。因此，遗迹化石可以提供一个独立的证据线来校准寒武纪大爆发。本项目的目标是：（1）记录寒武纪大爆发及其Fortunian前奏的遗迹动物群;（2）探索遗迹化石的潜力，以提高我们对生物圈历史上关键时期寒武纪生态系统建设的认识;以及（3）探索遗迹学信息如何提供对这个突破的时间和环境约束的见解，揭示了进化创新中潜在的历时性。

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.******