Faunal Differentiation Across Environment and Space During the GOBE in South China

The Great Ordovician Biodiversification Event (GOBE) marks one of the most profound changes in marine ecosystems in Earth history, with increased biodiversity observed across the globe. Numerous hypotheses have been proposed to explain the diversity change, but distinguishing amongst them requires biodiversity to be quantified across environments at both local and regional scales. Here, we present a high-resolution, assemblage-level dataset comprising 528 stratigraphic sections and 21,430 fossil occurrences from South China spanning the Furongian (late Cambrian) to the Middle Ordovician. We quantified changes in species richness and faunal composition across four depositional environments: littoral, platform, slope, and deep-shelf, and evaluated faunal turnover geographically and environmentally. Our results reveal that patterns of richness and faunal composition diverged across environments during the GOBE, and the rapid rise of regional richness was accompanied by increasing faunal differentiation across environments and space. We found local richness remained relatively stable, while the spatial extent of fossil-bearing environments expanded considerably during the GOBE. Taken together, these patterns suggest increasing sea level expanded shallow-marine shelf environments, which may have facilitated faunal differentiation in space and across environments, thereby contributing to the increase of marine diversity in South China during the Ordovician.