THE SHIBANTAN LAGERSTÄTTE AND TERMINAL EDIACARAN ANIMAL EVOLUTION

The terminal Ediacaran stage (ca. 550–539 Ma) sits at the joint between the Proterozoic and Phanerozoic eons, and is pivotal in deciphering the animal evolutionary history across the Proterozoic-Phanerozoic transition. Our knowledge about terminal Ediacaran marine ecosystems mostly comes from a handful of fossil assemblages hosted in siliciclastic sediments in Namibia, western United States, and South America. The Shibantan Lagerstätte (551–543 Ma) in the Yangtze Gorges area in South China is one of the few terminal Ediacaran fossil assemblages hosted in marine carbonate rocks. Thus, it offers a distinct perspective on terminal Ediacaran marine ecosystems and provides key data to test hypotheses about the evolutionary dynamics of animals vs. Ediacara-type organisms. The Shibantan Lagerstätte is taxonomically dominated by sessile and mobile benthic organisms, including rangeomorphs, arboreomorphs, erniettomorphs, palaeopascichnids, possible dickinsoniomorphs, tubular fossils, bilaterians, as well as abundant and diverse ichnofossils. Shibantan fossils preserve evidence for ecological interactions among mobile bilaterians, sessile benthic Ediacara-type organisms, and microbial mats, thus providing new insights into the decline of the Ediacara biota and the concurrent rise of macroscopic bilaterian animals across the Proterozoic-Phanerozoic transition.