Brachiopod biogeographic change during the Early to Middle Ordovician in South China

Biogeographic analysis of the Early to Middle Ordovician brachiopod fauna of South China shows close linkages to that of Laurentia during the Tremadoc, but as the South China block drifted away from Gondwana its faunal affinity gradually shifted to closer relationships with the terranes of Baltica, Avalonia, Sibumasu and southern Kazakhstan during the Floian to Darriwilian interval. Palaeobiogeographically, a major change of brachiopod faunal affinities in South China happened at the beginning of the Floian in the Tetragraptus approximatus Biozone, which is earlier than trends in the α- and β-diversity change. The first acme of brachiopod α-diversity change that occurred in the Didymograptellus eobifidus Biozone (middle Floian) in South China was manifested by modest increases of regionally distributed genera, together with expansion of cosmopolitan families, outweighing a decrease in endemic genera. It is postulated that South China served as a "cradle" for brachiopod biodiversification during the Early to Middle Ordovician, because there are more than 10 genera that had their earliest known occurrence in this region.