The Cambrian Explosion
The Cambrian Explosion
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DOI：
10.1007/978-94-017-9600-2_3
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发表时间：
2016-01-01
期刊：
影响因子：
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通讯作者：
Buatois, Luis A.
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文献类型：
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作者：
Mangano, M. Gabriela;Buatois, Luis A.
根据微量化石证据，寒武纪大爆发是生物圈历史上最引人注目的事件之一。技术数据作为身体化石记录和分子钟的独立证据，对于探索这一事件的本质和相关的进化创新具有很高的价值。与尸体化石相比，埃迪卡拉纪-寒武纪边界上的痕迹化石记录要连续得多，提供了有关生态系统多样化和建设的关键时期的信息。寒武纪早期显示出生物扰动结构的全球和阿尔法物种多样性和物种差异显着增加。典型的寒武纪建筑设计标志着动物与沉积物相互作用的新方式，记录了新角色的活动。显生宙初期，物种多样性和物种差异性的急剧增加支持了寒武纪爆发的假设，并且很难与这样的假设相一致：在寒武纪初期突然出现的尸体化石只是与矿化骨骼的获得有关的埋藏文物。通过比较埃迪卡拉纪-寒武纪边界的微生物垫保存窗口，进一步证明了这一事件的真实性质。埃迪卡拉纪岩石中明显缺乏诊断福图纪时代的独特、复杂的底下采矿策略。与寒武纪第2纪出现主要动物体图的身体化石记录相反，痕迹化石记录显示，主要的多样化事件发生在福尔图尼纪，允许相对较短的时间（约20 Ma）进行系统发育融合。后来发生的事， 寒武纪第二纪（即农业革命）。福尔图尼亚事件标志着与沉积物相互作用的新方式的建立，这种方式是由于独特的身体计划和广泛的行为策略的演变而产生的。以扩散为主的底栖系统中的沉积物推土，例如细粒近海沉积物的改造，是生态系统工程这一阶段的特征。生态系统工程中的第二个事件（寒武纪2）涉及生态结构的进化突破。该事件的地貌特征是由垂直深层悬浮供料器（例如 Skolithospiperock）主导的地貌结构记录的，揭示了平流主导的底栖系统中的生物扰动。悬浮摄食群落的建立，以及由多个鱼类群组成的更复杂的分层结构的存在，表明浮游生物与底栖生物的交换经过了精细校准，记录了寒武纪第二代的早期显生宙生态情景。尽管寒武纪爆发通常被认为仅限于正常海洋条件下的浅海环境（即海洋盐度和 生物学信息表明，深层、缺氧和边缘海洋环境，后者包括与公海相连的浅层潮间带环境和微咸水环境，也参与了这一进化突破。许多经典伯吉斯页岩（BS）型矿床中存在的痕迹化石为原位底栖群落提供了无可争议的证据。除了氧气（氧化还原不连续表面非常接近或位于沉积物-水界面）作为控制因素......
Based on trace-fossil evidence, the Cambrian explosion emerges as one of the most dramatic events in the history of the biosphere. Ichnologic data are highly valuable as an independent line of evidence with respect to the body-fossil record and molecular clocks to explore the nature of this event and the associated evolutionary innovations. In contrast to body fossils, the trace-fossil record across the Ediacaran–Cambrian boundary is far more continuous, providing information on a critical time of ecosystem diversification and construction. The early Cambrian displayed a remarkable increase in both global and alpha ichnodiversity and ichnodisparity of bioturbation structures.Typical Cambrian architectural designs signal new ways of animal–sediment interactions recording the activities of a new cast of characters. This dramatic increase in ichnodiversity and ichnodisparity at the dawn of the Phanerozoic supports the Cambrian explosion scenario, and is hard to reconcile with the hypothesis that the sudden appearance of body fossils near the beginning of the Cambrian is simply a taphonomic artifact related to the acquisition of mineralized skeletons. The real nature of this event is further proved by comparing the microbial mat preservational window across the Ediacaran–Cambrian boundary. Distinct, sophisticated, undermat mining strategies diagnostic of Fortunian age are strikingly absent in Ediacaran rocks. In contrast to the body-fossil record that places the appearance of the main animal body plans by Cambrian Epoch 2, the trace-fossil record shows than the main diversification event took place by the Fortunian, allowing for a relatively short time (approximately 20 Ma) of phylogenetic fuse.The Fortunian diversification event expressed by the appearance of a wide variety of trace-fossil morphologies was decoupled from the major shift in benthic ecologic structure that took place later, during Cambrian Age 2 (i.e., Agronomic revolution). The Fortunian event marks the establishment of novel ways of interacting with the sediment resulting from the evolution of distinctive body plans and a wide repertoire of behavioral strategies. Sediment bulldozing in diffusion-dominated benthic systems, such as reworking of fine-grained offshore deposits, was characteristic of this phase of ecosystem engineering. The second (Cambrian Age 2) event in ecosystem engineering involves an evolutionary breakthrough in ecologic structuring. The ichnologic signature of this event is recorded by ichnofabrics dominated by vertical deep-tier suspension feeders (e.g.,Skolithospiperock), revealing bioturbation in advection-dominated benthic systems. The establishment of suspension-feeding communities, in addition to the presence of a more complex tiering structure consisting of multiple ichnoguilds, suggests finely calibrated plankton to benthos exchange, recording an incipient Phanerozoic ecologic scenario already by Cambrian Age 2.Although the Cambrian explosion is commonly thought as restricted to shallow marine environments under normal-marine conditions (i.e., marine salinity and fully oxygenated), ichnologic information indicates that deep, oxygen-stressed- and marginal-marine environments, the latter including both shallow intertidal settings connected to the open sea and brackish-water embayed settings, were also involved in this evolutionary breakthrough. The presence of trace fossils in many classic Burgess Shale (BS) type deposits provides uncontroversial evidence of an in situ benthic community. In addition to oxygen (redox discontinuity surface very close to or at the sediment–water interface) as a controlling factor for the …