First record of the latest Devonian ostracods from Xainza region, Tibet, China: implications on palaeoenvironment and palaeobiogeography

Ostracods of the Devonian–Carboniferous transitional interval in the Lhasa Block are described for the first time at the stratotype section of the Chaguoluoma Formation, Xainza, Tibet. Fifty-three ostracod species of 19 genera are identified and figured including a new species Bairdiacypris xainzaensis n. sp. The ostracod fauna in the Chaguoluoma section may represent an age close to the Devonian–Carboniferous boundary. The benthic ostracods from the Chaguoluoma section belong to the Podocopid association (i.e., Eifelian Mega-Assemblage), which implies an offshore environment. Additionally, ostracods from the Chaguoluoma Formation show a high similarity to the Devonian taxa from South China, suggesting a close biogeographic affinity between the Lhasa Block and South China Plate. They are also compared to the ostracod faunas from Laurentia–Baltica, Gondwana, and Kazakhstan plates, which implies that ostracods could probably benefit from oceanic circulations and sea-level changes to experience faunal exchanges between peri-Gondwana and Laurentia–Baltica during the latest Devonian.