Ecology of the Ediacaran-Cambrian transition: The trace-fossil record

埃迪卡拉-寒武纪界线（541 Ma）代表了生物圈历史上的一个主要分界线。埃迪卡拉纪的生物群以软体生物为主，现在大部分被认为与现代后生动物无关。另一方面，寒武纪见证了几乎所有现代动物群体的快速发展，这是一个被称为寒武纪大爆发的重大进化事件。埃迪卡拉-寒武纪过渡期的演化研究大多基于体化石和分子钟的分析。然而，遗迹化石记录（包括动物留下的足迹、痕迹和洞穴）为校正寒武纪大爆发提供了独立的证据。虽然一些优秀的开创性论文已经考虑了这一转变的遗迹学，但仍然缺乏定量和系统的分析来测试寒武纪大爆发的时间和意义的相互竞争的假设。综合沉积学、遗迹学和地层学分析提供了对这些古老生态系统生态学的一瞥，特别有助于了解埃迪卡拉-寒武纪过渡期的底栖生物群落。该项目的目的是：（1）系统地评价生命史上这一关键时期的痕迹化石记录，（2）在层序地层框架内整合遗迹学和沉积学信息，以评价寒武纪辐射对沉积剖面的影响和程度。计划开展的活动包括：（1）在阿根廷、加拿大、南非、纳米比亚和伊朗的几个埃迪卡拉-寒武纪演替的野外工作，（2）修订关键的痕迹化石收集，（3）分析埃迪卡拉-寒武纪遗迹动物群数据库。生态学理论的最新发展和对遗迹化石的行为学意义的日益理解，为我们对生物圈历史上这一关键时期的看法取得重大突破铺平了道路。这项新的分析将提供一个更全面的图片的事件年表涉及寒武纪辐射，宏观进化和生态意义的这一重大事件。

The Ediacaran-Cambrian boundary (541 Ma) represents a major divide in the history of the biosphere. Ediacaran biotas were dominated by soft-bodied organisms that are now considered for the most part to be unrelated with modern metazoans. On the other hand, the Cambrian witnessed the rapid development of almost all modern groups of animals, a major evolutionary event known as the Cambrian explosion. The majority of evolutionary studies on the Ediacaran-Cambrian transition have been based on the analysis of body fossils and molecular clocks. However, the trace-fossil record (that consisting of tracks, trails and burrows produced by animals) provides an independent line of evidence to calibrate the Cambrian explosion. Although several excellent pioneering papers have considered the ichnology of this transition, there is still a lack of quantitative and systematic analysis to test the competing hypotheses on the timing and significance of the Cambrian explosion. Integrated sedimentological, ichnological and stratigraphical analysis provides a glimpse into the ecology of these ancient ecosystems and is particularly relevant to understanding the benthic communities of the Ediacaran-Cambrian transition. The aims of this project are: (1) to systematically evaluate the trace-fossil record across this critical interval in the history of life, and (2) to integrate ichnologic and sedimentologic information within a sequence-stratigraphic framework, in order to evaluate the impact and extent of the Cambrian radiation across a depositional profile. Planned activities include: (1) fieldwork in several Ediacaran-Cambrian successions in Argentina, Canada, South Africa, Namibia and Iran, (2) revision of key trace-fossil collections, and (3) analysis of a database of Ediacaran-Cambrian ichnofaunas. Recent developments in ecology theory and a growing understanding of the ethologic significance of trace fossils is paving the way for a major breakthrough in our view of this critical time in the history of the biosphere. This new analysis will provide a more comprehensive picture of the chronology of events involved in the Cambrian radiation, and of the macroevolutionary and ecological significance of this major event.