嘉宾（Guest）：Dr. Alida Bailleul （IVPP） 

讨论主题（Topic）：Early avian evolution under the microscope 

时间（Time）：2019.4.9（周二）下午 3:00 — 4:00 

地点（Location）： 南楼321室

内容简介： 

       Skeletal and soft-tissues are important vessels capable of shedding light on unknown aspects of the biology of extant vertebrates. Here, the focus will be made on selected avian tissues that inform on the evolution of the reproductive system in stem birds.  

       First, the tissues of a new enantiornithine specimen (Lower Cretaceous Xiagou Formation; IVPP V25371) with an unlaid egg two-dimensionally preserved within its abdomen will be described. The findings recovered from the microstructure of both the egg and the femur will be discussed into a broader phylogenetic context. 

       Lastly, some fragments of purported ovarian follicles from an enantiornithine from the Jehol Biota (STM10-12) are described histologically in an attempt to shed light on the specific tissues preserved. Methods of analysis include standard paleohistology, paraffin histology, paleohistochemistry, scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The fossil tissues are compared to those of chicken ovarian follicles, and to a fossil seed preserved in Jeholornis (IVPP V13274) because of the persistent hypothesis that these structures were misidentified and are in fact digested seeds. These preliminary histological findings, and their implications for our understanding of the early evolution of the avian reproductive system, will be discussed. These new types of microscopic analyses must be encouraged and further perfected not only as a means to provide further insight into the evolution of all extinct vertebrates beyond their mineralized skeletons, but also as a way to verify identifications and test hypotheses based on macroscopic observations.