EAPSI: Documenting the Geological Controls that Influenced the Exceptional Preservation of Trilobites from 520 Million Years Ago in Southwestern China

保存完好的软体生物和三叶虫化石部分来自早寒武世(5.2亿年前)，非常罕见，但对于了解地球上最早的动物的进化具有重要意义。了解导致它们作为化石保存下来的地质过程，有助于我们了解长期快速、反复的环境变化如何影响早期动物的生物多样性。该项目将与位于中国的云南大学的张锡光博士合作，研究中国西南部两个早寒武世化石组合的保存和沉积控制，这些化石组合含有罕见的、保存极为完好的三叶虫和软体生物。这次合作提供了一个机会，可以接触到这些到目前为止只在中国发现的早寒武世化石。这些组合赋存于中国昆明附近红景绍组两个不同厚度的泥岩层中。地质上较年轻的组合包含所有发育阶段的完全关节到部分关节的三叶虫，属于典型的张山物种；该组合还包含许多软体生物。相反，地质上更古老的组合由一簇簇成熟的三叶虫标本组成。这项研究将涉及对每一张1米床层进行逐层解剖，以便将编织细节(例如，方位、姿势、关节状态、是否存在软体保存、聚集等)化石的一部分将被记录下来。这些特定于地层的数据将被顺序数字化到地理信息系统(GIS)数据库中，然后在这个地层精细尺度上对它们进行空间和时间评估，以便在两个挖掘区段之间进行挖掘学和行为比较。这项研究将提供有关环境过程的新信息，这些过程导致了早期进化历史中动物生命的特殊但罕见的保存。该NSF EAPSI奖是与中国科技部合作资助的。

Well-preserved fossilized parts of soft-bodied organisms and trilobites from the early Cambrian (520 million years ago) are exceptionally rare but are significant for understanding the evolution of Earth's earliest animals. Understanding the geological processes that lead to their preservation as fossils sheds new light into how rapid, repeated environmental changes over long intervals of time affected the biodiversity of early animals. In collaboration with Dr. Xiguang Zhang at the Yunnan University in China, this project will investigate the preservational and depositional controls of two early Cambrian fossil assemblages from Southwestern China bearing rare, exceptionally well-preserved trilobites and soft-bodied organisms. This collaboration affords an opportunity to have access to these early Cambrian fossils recovered thus far only in China. These assemblages are contained within two different 1 m thick mudstone beds of the Hongjingshao Formation near Kunming, China. The geologically younger assemblage contains fully articulated to partially articulated trilobites of all developmental stages belonging to the species Zhangshania typical; this assemblage also contains numerous soft-bodied organisms. Conversely, the geologically older assemblage comprises of clusters of mature specimens of the trilobite Hongshiyanaspis sp. This study will involve dissecting each 1 m bed layer by layer so that taphonomic details (e.g., orientation, posture, state of articulation, presence of soft-bodied preservation, clustering, etc.) of the fossils will be recorded. These bed-specific data will be sequentially digitized into a Geographic Information Systems (GIS) database, where they will then be assessed spatially and temporally at this stratigraphic fine scale to allow for taphonomic and behavioral comparisons to be made between the two excavated sections. This study will contribute new information concerning the environmental processes that led to the exceptional, but rare, preservation of animal life during its early evolutionary history. This NSF EAPSI award is funded in collaboration with the Chinese Ministry of Science and Technology.