Latest Permian acritarchs from South China and the Micrhystridium / Veryhachium complex revisited.

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 generaMicrhystridium,VeryhachiumandLeiosphaeridia. However, larger taxa with vesicles often exceeding 80 μm in diameter, such asDictyotidium, are also abundant in the Shangsi section. Due to the presence of large populations ofMicrhystridiumandVeryhachium, a simple classification scheme for theMicrhystridium/Veryhachiumcomplex is proposed, based on the geometrical shape of the vesicle. We propose dividing the complex into five groups: theVeryhachium cylindricumgroup, representing all ellipsoidal specimens; theVeryhachium trispinosumgroup, all with triangular-shaped vesicles; theVeryhachium lairdiigroup, all with rectangular forms; theMicrhystridium pentagonalegroup, all with pentagonal specimens; and theMicrhystridium brevegroup, which includes all spherical forms. [ABSTRACT FROM PUBLISHER]