Middle Cenozoic micromammals from Linxia Basin, Gansu Province, China, and their implications for biostratigraphy and palaeoecology

(Uploaded by Plazi for the Bat Literature Project) We report late Oligocene to late Pliocene micromammal assemblages from 19 localities of the Linxia Basin of Gansu Province, China. Abundant material (> 7000 specimens) includes members of Eulipotyphla, Chiroptera, Rodentia and Lagomorpha, and comprises 121 species arranged in 24 families. The Yagou assemblage (basal part of the Jiaozigou Formation) is one of the few early Late Oligocene micromammalian faunas known from China. The Galijia (Dongxiang Formation) and Yihachi ("Liushu" Formation) assemblages represent the richest and most productive middle and late Miocene micromammal faunas known from northwestern China. These middle Cenozoic faunas show a closely similar community structure and taxonomic composition, and a similar pattern of faunal turnover, with contemporary faunas throughout the Mongol-Xinjiang Region, implying the existence of a unified biogeographic zone. The discoveries contribute to the temporal ordering of individual fossil assemblages of northern China and help develop a framework for Cenozoic biostratigraphy and biochronology in central Asia. Our palaeoenvironmental analysis suggests change towards warmer and moister equable habitats of the late Oligocene to early and middle Miocene, followed by the onset of drier temperate shrub-steppe environments. The composition of extant families of micromammals that developed during the Neogene reflects a faunal distribution analogous to the Holarctic Region today and suggests a shared ecology.