On the basis of morphological and taphonomic study of a large sample population, Miaohephyton bifurcatum Steiner, emend. from the terminal Proterozoic Doushantuo Formation (600-550 Ma), South China, is interpreted as algal fragments shed from their parent thalli for reproductive or environmental reasons. Characters such as regularly dichotomous, multicellular thalli with forked tips, apical and intercalary meristematic growth, abscission structures, and possible conceptacles collectively suggest an affinity with the brown algae, in particular the order Fucales. In conjunction with reports of xanthophyte fossils in older Neoproterozoic rocks, this reinterpretation of Miaohephyton bifurcatum indicates that photosynthetic stramenopiles (chrysophytes, synurophytes, xanthophytes, phaeophytes, and diatoms; or chromophytes sensu stricto) diversified during the Neoproterozoic Era along with the red and green algae. This, in turn, suggests that the secondary endosymbiosis that gave rise to the photosynthetic stramenopiles took place relatively soon after the evolutionary transformation of cyanobacteria to rhodophyte plastids.

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