Carapace growth in modern and fossil Spinicaudata (Crustacea: Branchiopoda): testing its applicability in unravelling Middle Jurassic to Late Cretaceous lacustrine faunal turnover in NE China

脊椎动物甲壳类在泥盆纪成为湖泊群落的重要组成部分。在3亿多年的时间里，它们一直保持着高度丰富的状态，主导着湖泊无脊椎动物群落。在早白垩世全球多样性高峰之后，晚白垩世全球多样性急剧下降，并在早新生代将其排除在湖泊环境之外。化石记录中棘尾动物存在的减少构成了湖泊生态系统一般演化的一个重要方面。今天，棘尾目代表着一个生态专门化分支，适应于临时的、新鲜的到低盐湿地，这些湿地通常不支持营养水平较高的动物。该项目旨在通过计算大型底栖动物群落组成随氧、温度和养分有效性环境梯度的变化速率，来揭示东北中国地区中侏罗世-晚白垩世湖泊动物群落更替的控制因素。将为四个目标地层的每个化石层面编制生物地球化学替代数据(Delta15N、Delta13Corg、Corg/N、GDGT生物标志物)，以进行进一步的统计测试。许多层面包含单一的棘尾类组合，使得甲壳形态成为湖泊生态系统变化的另一个重要信息来源。化石形态沿环境梯度的变化模式将与拟议的饲养实验的结果进行比较，这些实验旨在研究氧气、营养物质的可用性和温度对现代物种甲壳生长的影响。

Spinicaudatan crustaceans became important elements of lake communities during Devonian times. They remained highly abundant for more than 300 million years, dominating the lacustrine invertebrate community. The Early Cretaceous global diversity peak was succeeded by a proposed dramatic decline during the Late Cretaceous and their exclusion from lake environments during the early Cenozoic. That decline of spinicaudatan presence in the fossil record forms an important aspect of general lake ecosystem evolution. Today, Spinicaudata represent an ecologically specialized clade adapted to temporary, fresh- to oligohaline wetlands that commonly do not support animals of higher trophic levels. The project aims at unravelling factors that controlled lacustrine faunal turnover in Middle Jurassic–Late Cretaceous fossillagerstätten of NE China by calculating the rate of change in macrobenthic community composition along environmental gradients of oxygen, temperature and nutrient availability. Biogeochemical proxy data (delta15N, delta13Corg, Corg/N, GDGT biomarkers) will be compiled for each fossiliferous bedding plane of four targeted formations for further statistical testing. Numerous bedding planes contain monospecific assemblages of Spinicaudata, rendering carapace morphology an additional important source of information for lake ecosystem change. Patterns of fossil morphological change along environmental gradients will be compared with results of proposed rearing experiments that target effects of oxygen, nutrient availability and temperature on carapace growth in modern species.