Polystrata alba (Pfender) Denizot, 1968 (Peyssonneliaceae, Rhodophyta) in Late Eocene algal limestones of the Upper Austrian Alpine Foreland Basin forms (1) horizontal crusts, (2) subspherical and irregular, unilayered rhodoliths with sediment-filled inner cavities, and (3) rhodoliths. Most of the described growth forms are unique and previously have not been described from fossil material. Comparisons with present-day analogues, however, reveal that most growth features can be explained by the interplay between sediment input and bottom stability. This actualistic approach allows the reconstruction of paleoecologic and taphonomic processes that influenced both growth forms of P. alba and the resulting sedimentary facies. The model described in this study provides a useful tool for the reconstruction of paleoenvironmental conditions.

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