海相遗迹化石对显生宙生物大辐射事件的响应*

通过系统梳理前寒武纪和显生宙海相遗迹化石记录及笔者自己的研究,发现在寒武纪生命大爆发、奥陶纪生物大辐射、中生代海洋革命共3次里程碑式的生物大辐射过程中,海相遗迹化石的属级多样性变化和歧异度增减均与生物多样性呈正相关,生物扰动强度和深度明显增加,造迹生物的觅食策略和行为习性多样化明显增多。寒武纪生命大爆发时期,最有代表性的生物行为变化是出现了具有垂向分量的潜穴; 奥陶纪生物大辐射期间,海相遗迹化石的分布逐渐从滨、浅海扩展至半深海和深海,表现为造迹生物群落栖息地的扩张; 中生代海洋革命时期,海相和陆相遗迹化石同步增加,生物对生态空间利用的深度、广度和集约性同步增强,遗迹化石面貌表现为深海雕画迹的多样性和歧异度大幅增加、形态类型多样、多种觅食策略共存。地史时期的海相遗迹化石面貌受环境外因和生物内因控制,表现出形态由简到繁、分布范围由小到大的变化趋势,对生态空间的利用表现为由沉积物表层至浅层再到深层、由二维到三维、由局域(浅水)到广域(浅水和深水以及陆地)的发展,印证了生物获取生态机会的过程。

Marine ichnofossils as a record of major biodiversification events in the Phanerozoic

In this paper,we analyzed the trace fossil records of the major Phanerozoic biodiversification events,including the Cambrian Explosion,the Great Ordovician Biodiversification Event,and the Mesozoic Marine Revolution. The ichnodiversity and ichnodisparity of marine trace fossils show a positive correlation with biodiversity during these three biodiversification events. The intensity and depth of bioturbations both increased distinctly. The feeding strategies and the behavior of marine trace-makers became more complex. The most prominent change in the trace-making behavior during the Cambrian Explosion is the appearance of vertical burrows(or vertical elements in burrows). The shallow-marine ichnofauna expanded to the bathyal-marine and deep-marine environments during the Ordovician,as represented by the appearance of morphologically complex deep-marine trace fossils. It shows a further intensification of the exploitation of the marine benthic ecological niches in the Cretaceous. Characteristic change during this period is the significant diversification of deep-marine graphoglyptids,with the development of multiple morphological types and feeding strategies. Under the influences of the environment and biotic changes,marine ichnofaunas became more complicated in morphology and ethology and adopted progressively wider environmental distribution during the Phanerozoic. The marine ichnofaunas displayed increasing penetration depth,transferred from two-dimensional to three-dimensional structures,and radiated from the shallow shelf to the deep sea and continent. These features may be attributed to the process that organisms acquire ecological opportunities.