An exceptionally preserved fossil assemblage from the early Jurassic of Chongqing (China) reveals a complex lacustrine ecosystem.

One of the five greatest mass extinction events in the history of life occurred at the end of the Triassic (~ 201 million years ago), as confirmed by profound loss of life in marine realm. Terrestrial ecosystems were also suffered but the extent of life loss and timing of subsequent recovery remain equivocal, largely because of scarcity of fossil record. Here we report an exceptionally-preserved fossil assemblage, Yuzhou Biota, from the Sinemurian (~ 199-193 Ma), Early Jurassic lacustrine deposits of northern Chongqing, China. The biota documents the first known trophically complex lacustrine ecosystem after the end-Triassic extinction in China, including various representative species ranging from primary consumers (e.g., ostracods, conchostracans, gastropods and bivalves) to large predators (e.g., a variety of jawed fishes and pliosauroids). The most striking feature is its diversified aquatic vertebrates; the hybodontiforms, ceratodontiforms, ptycholepiformes, ginglymodians and pliosauroids from the biota all represent their first occurrences above the Triassic-Jurassic boundary in China. As such, the discovery enriches our understanding of the faunal turnover of aquatic vertebrates following the end-Triassic mass extinction, and provides a novel window on the Early Jurassic lacustrine ecosystems.