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Resource pulses, occasional events of ephemeral resource superabundance, represent a fundamental mechanism by which energy, nutrients, and biomass are transported across ecotones. They are widespread in extant ecosystems; however, little is known about their deep-time record. We report the earliest-known mayfly swarm from the Early Jurassic Xiwan biota of southern China. Our taphonomic and sedimentological analyses show that these mayflies were buried on the bottom of a calm lake after post-mating death. Our suite of analyses suggests that the complex mating-swarm behavior was already well established in mayflies by the Early Jurassic. More importantly, our find represents the earliest-known resource pulse of insects, a mechanism that can play a substantial role in nutrient transport from aquatic ecosystems to surrounding terrestrial ecosystems. Such an aquatic-terrestrial ecosystem linkage may be a key novelty in Mesozoic lacustrine ecosystems. Our results high-light the underappreciated ecological significance of insects in deep-time terrestrial ecology.

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We present vegetation reconstructions based on an almost complete succession through the Triassic of Tulong, Nyalam County, southern Xizang (Tibet), China. The Permian and earliest Triassic samples were barren of palynomorphs, however, in overlying strata we identified well-preserved and diverse miospore assemblages. Seven pollen and spore zones spanning the Olenekian to the Rhaetian were recognized. These palynological zones were amalgamated into three floral stages that comprise distinct vegetation types: (1) an early Olenekian lycophyte dominated flora with common pteridosperms, indicative of a warm and dry climate; (2) a late Olenekian transitional flora composed of abundant conifers with low abundances of lycophytes, signifying a decrease in temperature and increase in humidity; (3) a Middle to Late Triassic mature conifer-dominated flora with diverse sphenophytes, ferns and cycadophytes, indicative of a stable, temperate and humid climate. The changes in vegetation and climate tentatively correlate with the rifting of northern Gondwana, suggesting that regional tectonics was a contributive driving factor to local floral community change. This work was also supported by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (grant numbers XDB26010206, XDB18000000, XDB03010103), the National Natural Science Foundation of China (grant number 41688103), Key Laboratory of Economic Stratigraphy and Palaeogeography, Chinese Academy of Sciences (grant number 2017KF07), UNESCO grant IGCP 632.