Early–Middle Ordovician brachiopod diversification in the middle Yangtze region of South China

Abstract

The evolution of the Early–Middle Ordovician brachiopod diversity in the middle Yangtze region of South China has been analyzed. The brachiopods in this region originated in the early Tremadocian and radiated from the late Floian to the late Dapingian. The composition of rhynchonelliformean brachiopods underwent major changes in the late Floian, and endemic genera migrated from the upper Yangtze region to replace the cosmopolitan genera. A global comparison of the brachiopod diversity curves of South China, Laurentia, and Baltica reveals that (1) the processes and scales of brachiopod radiation in different paleocontinents were distinct; (2) unlike the global evolution of graptolites and chitinozoans, the correlation between brachiopod diversification and regional habitat change was more obvious, and the impact of habitat heterogeneity was reflected not only between plates but also in the interior of the plates, such as the closely connected middle and upper Yangtze regions of South China; and (3) geographical isolation was a key factor in the differential radiation on different paleocontinents.