晚石炭-早二叠世华南蜓类有孔虫的形态分异及其生态指示意义

Paleoecology involves study of the relationships that fossil organisms have with their natural environment, and is one of the most important subjects of Paleobiology. It offers a better way to understand the coevolution of organisms and environment. Permo-Carboniferous has a pivotal role in the Late Paleozoic Ice Age(LPIA). Marine environment distinctly changed with the sea level fluctuation and temperature shift. Evolutionary rates of marine invertebrates were supressed to a rather low level. However, fusulinid, one of the extinct larger benthic foraminifera, diversified rapidly during this period, resulting from its sensitivity to environmental change, and therefore made it an ideal object for the research on relationship between organisms morphologic diversification and environmental changes during LPIA. This project chooses the South China as work area for containing varied carbonate facies sections and abundant fusulinid fossils. Here an interdisciplinary research including paleontology, sedimentology, geochemistry will be carried out and aimes for the relationship between fusulinid morphologic diversification and environmental changes. Morphologic characteristics of fusulinid species from different sections implying facies gradient under similar temperature during the same period will be statistically summarized. Meanwhile morphologic evolution of different fusulinid taxa possibly mainly due to temperature and salinity changes during the glacial will be detailed analysied. Afterwards those results will be used to compare with the changes of environmental factors, such as temperature, light, water energy, nutrition supply, salinity and others, resulting from facies and geochemistry analyses, to disclose the essential link. Moreover, study on fusulinid morphology will be conducted to clarify its adaptative traits and ecological implication, and further, to help understand the evolution of fusulinid and dynamics of earth ecosystem during LPIA.

探究地质历史时期生物体与周围环境之间相互关系的古生态学是古生物学研究的重要内容，是深入理解生物与环境协同演化过程的重要途径。晚石炭-早二叠世是晚古生代冰期发育的最关键时期，海洋环境发生显著的变化，海洋无脊椎生物世界的演化因而极其缓慢。但蜓类有孔虫却大规模辐射分异，显示出对环境变化的高度敏感，是研究冰期生物形态分异与环境变化关系的理想对象。本项目选择沉积相发育多样化、蜓类化石丰富的华南地区作为工作区域，研究蜓有孔虫在晚石炭-早二叠世不同沉积相区的形态分异，以及不同蜓类群在整个环境变化过程中的形态演化，并通过沉积学、地球化学等方法，考察不同沉积相区以及海洋环境变化过程中各项环境因子的变化特征，综合分析蜓类形态分异与各环境因子之间的相关关系，探索蜓类的生态适应机制，挖掘蜓类形态分异的生态指示意义，以深入理解晚古生代冰期蜓类有孔虫的演化过程及地球生态环境的变化。

蜓类有孔虫是晚古生代的标志化石，长久以来都在地层划分和对比中显示着重要的作用。作为海洋底栖生物，它们对生态环境敏感，其分异度、丰度、形态变化等都是反映环境变化的良好指标。本项目计划即紧扣这一目标，从蜓类的形态分析、动物群特征分析以及与环境变化的响应关系等方面展开研究。. 蜓类有孔虫的形态分析长期以来都仅限于定性的主观判定，缺乏统一、客观的定量标准。针对此，项目组运用定量化的形态测量学方法，将蜓类个体发育阶段形成的各外壳轮廓作为样本，比较得到它们的形态差异，由此形成的曲线即蜓类个体发育过程的形态变化曲线。此曲线不仅量化了蜓类自身发育过程中的形态变化，更可以作为不同蜓类群之间的形态差异比较基础。运用这一方法分析得到：早二叠世假希瓦格蜓亚科中的重要类群，壮希瓦格蜓和球希瓦格蜓在个体发育过程中呈现出显著差异，可能是导致它们地理分布范围不同的原因。对华南假希瓦格蜓亚科所有类群的分析，显示出这一类群在个体发育过程中均存在异速生长过程，导致了壳体的巨大化。 . 二叠纪时处于冈瓦纳特提斯区的云南保山、腾冲地块，一直以来都是“非适宜环境”下蜓类动物群分异的代表区域。项目组的研究表明，这两个地区的蜓类动物群均以低分异-高丰度为特征，尤以早二叠世的动物群为代表。对腾冲地块蜓类动物群的研究详细考量了赋存蜓类的沉积相水动力条件，证明蜓类动物群的低分异-高丰度特征与生活环境的水动力条件无显著关联，可能与温度条件不适有关。. 要进一步探求蜓类动物群的形态分异与环境条件的影响，需要借助地球化学的手段。项目组从形态较为相似的现代有孔虫入手，寻找可能一致的环境响应方式，可能是间接反映蜓类有孔虫生态适应的一个有效途径。针对现代大型底栖有孔虫展开的初步研究显示，Mg、Na、Sr、Si、B、Fe元素在有孔虫壳体中的含量较高，且在同种的不同个体之间差异较小，可用于探究不同形态类群对相同环境条件的响应。