Proterozoic phytoplankton and timing of Chlorophyte algae origins

Abstract

Abstract: Morphological and reproductive features and cell wall ultrastructure and biochemistry of Proterozoic acritarchs are used to determine their affinity to modern algae. The first appearance datum of these microbiota is traced to infer a minimum age of the divergence of the algal classes to which they may belong. The chronological appearance of microfossils that represent phycoma-like and zygotic cysts and vegetative cells and/or aplanospores, respectively, interpreted as prasinophyceaen and chlorophyceaen microalgae is related to the Viridiplantae phylogeny. An inferred minimum age of the Chlorophyte origin is before c.1800Ma, the Prasinophyceae at c.1650Ma and the Chlorophyceae at c.1450Ma. These divergence times differ from molecular clock estimates, and the palaeontological evidence suggests that they are older. © The Palaeontological Association.