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

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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.