An international research team led by Prof. WANG Bo from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS), together with Dr. ZHANG Qianqi from Shenyang Normal University and other collaborators, has discovered a diverse fossil insect assemblage from the Lower Jurassic Xiaomeigou Formation in Dachaidan Town, Qinghai Province. Named the Dachaidan Entomofauna, the discovery provides critical insights into the evolution of Mesozoic insects on the Qinghai-Tibetan Plateau.

The results were published in Fundamental Research on April 17.

The Qinghai-Tibetan Plateau, also known as the "Roof of the World," is a global hotspot for geological research. Although Cenozoic insect fossils have been relatively well documented, the evolutionary history of insects on the plateau during the Mesozoic era remains largely unknown.

The newly discovered Dachaidan Entomofauna is dominated by beetles (Coleoptera, 48%), followed by cockroaches (Blattodea, 26%), stoneflies (Plecoptera, 12%), and bugs (Hemiptera, 6%). Among these, the beetles are mainly archostematans and polyphagans, with some specimens preserving exquisite microstructural details. 

The presence of both terrestrial insects (beetles, cockroaches, and bugs) and aquatic stoneflies (adults and nymphs) indicates that these insects inhabited a swamp environment, consistent with the coal-bearing fluvial sequences of the Xiaomeigou Formation.

The stoneflies belong to the extinct family Perlariopseidae, a key group for Jurassic–Cretaceous stratigraphic and palaeoecological correlation across Asia. Notably, the aquatic insect assemblage from Dachaidan represents a unique hypotrophic ecosystem, characterized by a detritivore-based aquatic food web, where primary production consisted largely of terrestrial organic detritus and dead benthic algae. 

Previously, such ecosystems were thought to exist only in the Early Jurassic–Early Cretaceous period in southern Siberia, western Mongolia, and northern Kazakhstan. The Dachaidan Entomofauna thus marks the first record of this ecosystem type in China.

Compared with other Early Jurassic entomofaunas in China, the Dachaidan assemblage has distinctly different taxonomic compositions and palaeoecological features, highlighting significant regional differences among Early Jurassic insect faunas on different tectonic plates in China. 

The discovery provides direct evidence for reconstructing the palaeogeographic distribution of Jurassic insect assemblages and offers insight into the evolution of terrestrial ecosystems on the Qinghai-Tibetan Plateau during the early Mesozoic era. It further underscores the plateau's immense potential as a fossil treasure trove.

This study was supported by the National Natural Science Foundation of China, the Second Tibetan Plateau Scientific Expedition and Research, and the Doctoral Research Start-up Foundation of Liaoning Province.

Representative fossils from Dachaidan Entomofauna (a) stonefly (Plecoptera: Perlariopseidae Sinitshenkova, 1985); (b) cockroach (Blattodea: Caloblattinidae Vršanský & Ansorge, 2000); (c) beetle (Coleoptera: ZygadeniaHandlirsch, 1906); (d) cockroach (Blattodea: Caloblattinidae Vršanský & Ansorge, 2000); (e, f) beetle (Coleoptera: Zygadenia Handlirsch, 1906); (g, h) stonefly nymphs (Plecoptera). (Image by NIGPAS)