Morphological variability in Alveolophora areolata (Moisseeva) Moisseeva and Alveolophora bifaria Nevretdinova & Moisseeva.

The morphological variability of two biostratigraphically important diatom species of the Russian Far East, Alveolophora areolata (Moisseeva) Moisseeva and Alveolophora bifaria Nevretdinova et Moisseeva,was studied using light and scanning electron microscopy. High variability was found in mantle height, diameter, stria organization, areola location on the valve face, alveolus structure and costae of A. bifaria, but less variability in A. areolata. Separation valves of A. areolata lack spines, and rimoportulae were found on the valve face for the first time. Based on the new morphological data, descriptions for these taxa have been emended. [ABSTRACT FROM AUTHOR]