Diverse and well-preserved latest Permian phytoplankton assemblages are described from four sections of the Yangtze Block, South China from localities in Zhongzhai (Guizhou Province), Shangsi (Sichuan Province), Xiakou (Hubei Province) and Dongpan (Guangxi Province). Most of the species have been reported previously from other upper Permian sections worldwide. The South Chinese phytoplankton taxa are generally very small in size, usually displaying diameters of about 20 μm and commonly include the genera Micrhystridium, Veryhachium and Leiosphaeridia. However, larger taxa with vesicles often exceeding 80 μm in diameter, such as Dictyotidium, are also abundant in the Shangsi section. Due to the presence of large populations of Micrhystridium and Veryhachium, a simple classification scheme for the Micrhystridium/Veryhachium complex is proposed, based on the geometrical shape of the vesicle. We propose dividing the complex into five groups: the Veryhachium cylindricum group, representing all ellipsoidal specimens; the Veryhachium trispinosum group, all with triangular-shaped vesicles; the Veryhachium lairdii group, all with rectangular forms; the Micrhystridium pentagonale group, all with pentagonal specimens; and the Micrhystridium breve group, which includes all spherical forms.

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