HIGH-RESOLUTION INVESTIGATION OF INVERTEBRATE MARINE COMMUNITIES FROM GUIZHOU, CHINA FOLLOWING THE LATEST PERMIAN MASS EXTINCTION EVENT

The Permian-Triassic transition is a key interval for the evolution of modern marine ecosystems. The timing of the key radiations and changes in ecosystem structure are poorly understood, but the immediate extinction aftermath is becoming increasingly recognized as a key interval for the diversification of many marine animals. To investigate the diversification of the benthos and changes in ecological parameters during this critical interval, we undertook a high resolution study of the post-extinction microbialite unit by investigating 83 paleoecological samples from the Great Bank of Guizhou, an isolated shallow marine platform in the Nanpanjiang Basin of south China. Here we recognize 52 benthic invertebrate species from 4373 individuals, including three new bivalve, and three new gastropod species. This raises the diversity of the Great Bank of Guizhou basal microbial unit to 91 invertebrate species. 71% of the genera are Permian holdovers, whilst only 18% of the species are Permian holdovers. This new data records no temporal trends in the richness, composition, or body size of the benthos during the deposition of the microbialite unit. The benthic community is both ecologically and taxonomically diverse, recording articulate brachiopods, lingulids, crinoids, echinoids, bivalves, gastropods, microconchids, foraminifera, and ostracods. The small body sizes of the benthic community, and the large lophophoral cavity in the lingulids suggests that these animals lived in a highly stressed environment. We propose that the microbialite unit contains a survival fauna in an interval that represents persistent environmental stress from the late Permian climate event, associated with deoxygenation, high sea surface temperatures, and elevated primary productivity.