若干寒武纪三叶虫类群躯体分节进化发育模式

Arthropods are characterized by a segmented body with hardened exoskeletons and jointed appendages, from which derived anatomic data are conventionally regarded as being potentially significant in their systematic and evolutionary studies. Abundant and highly diversified trilobites have been well discovered throughout the Paleozoic, consisting of one of the most distinct arthropod groups. However, our knowledge about the evolutionary development of trunk segmentation of many trilobite branches during the Cambrian radiation is scarce, and hypotheses on this aspect remain controversial. Based on numerous phosphatized eodiscoid exoskeletons collected from the Cambrian of southern China, in this study we attempt to verify some skeletal microstructures, such as tiny marginal spines, gland pores and bristles (or setae), may come into being in accordance with the development of trunk segments. That is, the relatively easy determination of such microstructures may offer a reliable way to mark the trunk segments during ontogenetic development. On this basis, this study, as relying on convincing information derived from their own ontogenetic and anatomic analyses, along with inference of soft body anatomy of some contemporaneous arthropods with Orsten-type preservation, may substantially reveal the essential mode of trunk development and segmentation for eodiscoid trilobites. In addition, this approach will set up a sound base for comparison of trunk segmentation among eodiscoids and some other trilobites that have had their trunk developments been well examined. By theoretical analysis this specimen-based study is expected to provide fresh insights into the evolutionary developmental origin and paleobiology of trunk segmentation for the specialized eodiscoids, as well as other Cambrian trilobite groups.

分节的躯干和附肢是节肢动物最显著的形态特征，其蕴含的基本信息，历来被认为有着潜在重要的系统分类和进化意义。三叶虫是古生代最常见的节肢动物，然而，至今我们对其寒武纪许多代表支系的基本躯体构建、个体发育及早期辐射分异仍感模糊并存在种种争议。大量来自华南寒武系精美保存的磷酸盐化盘虫三叶虫显示：其背壳的一些细微构造，如小刺、腺孔和瘤粒，与其体节大致存在一一对应的内在联系。基于此，依据源自其个体发育和微观形态解剖证据，借鉴三维保存的奥斯坦型（Orsten-type）节肢类随生长显现的详尽形态、结构变异（包括躯干的分节）规律，以识别盘虫三叶虫不同属种体节的增生方式，确认该类群的基本分节模式，并与其它一些个体发育得到详尽研究的三叶虫的躯体分节综合比较，辨析它们分节模式可能存在的异同。从而以合符逻辑、富于新意的思路，探讨这些三叶虫类群的发育、演化和系统分类，力争在理论上能有所突破。

本项目除致力于寒武纪三维保存的磷酸盐及奥斯坦型 (Orsten-type) 化石，还拓展研究了昆明东郊新近发现的布尔吉斯型保存的小石坝化石库 (Lagerstätte)。相关成果可概述如下：..小石坝的抚仙湖虫类 (fuxianhuiids) 展现出一种独特的“背甲掀开”保存模式，清楚显现了该原始节肢类头部组构和特化附肢类型，澄清了以往的谬误，为寒武纪节肢动物系统分类和早期演化提供了至关重要的实证。..叶足类Collinsium ciliosum发育了超乎想象复杂的背刺组合和用于滤食特化的附肢，表现出比其他近亲类群和现生的有爪动物更显著的形态分异和附肢的复杂化，因此在寒武纪大爆发期间开拓出独自的生态空间。..三叶虫Gunnia早期龄虫的磷酸盐化背壳显示，一最初出现在尾轴末端微小的“稚节”(immature ring)，在以往研究中多被忽视。传统生长阶段的划分不过是将一连续的发育过程予以人为粗略的界定。这些来自细微处的证据为探索三叶虫个体发育提供了新思路和有意义的信息。..此外，本研究还报道了小石坝化石库中罕见的骨片呈组合状态的Wiwaxia，及其独特的生活模式；论证了适应捕食生活的双壳瓣节肢类Clypecaris serrata；剖析消化道得以保存的鳃曳类，重新认识其取食习性、生活模式。贵州都匀不同类型磷酸盐化粪化石的发现喻示寒武纪底栖生物群已出现复杂营养结构和营养习性组合。首次在昆明寒武系第4统乌龙箐组发现高度被甲的叶足类Collinsium sp.， 延伸了“柯林斯怪”(Collins' monster) 的地理和地层分布。发现埃迪卡拉系陡山沱组显示右旋结构的球形微体化石，探讨了这类曾经被鉴定为藻类、胚胎或其他生物类群微体化石的分类位置及其生活周期。描述了具有较为完整不同生长阶段龄虫、独特的个体发育模式贵州瓮安寒武系的掘头虫三叶虫Duodingia。..本项目共完成SCI论文10篇（包括1篇《Nature》和1篇《PNAS》）；获得2015年度云南省自然科学一等奖。