A new Sellaphora Mereschkowsky species (Bacillariophyceae) from Hainan Island, China, with comments on the current state of the taxonomy and morphology of the genus

We present light and scanning electron microscope observations on a new species of the diatom genus Sellaphora, Sellaphora wangii Y.Liu & Kociolek, sp. nov., described from Hainan Island, China. This species has a raised conopeum with an axial groove or trough on either side of the axial area containing striae extending into the trough, and round depressions (i.e. pits) on the valve mantle at both apices. Our new species is distinctive and separated from other Sellaphora taxa by a unique combination of features that includes its valve outline, undulate raphe, and bow-tie shaped hymenes of the internal areola openings. The uncertainty and dynamic nature of the classification of Sellaphora prompted a review of the ultrastructural features found in species assigned to the genus. Based on this review, we identify four distinct groups of Sellaphora taxa organized by different combinations of ultrastructural features: stria structure, external and internal openings of the areolae, conopeum, polar bars, and apical pits. Based on the features present in our new species, it would be placed in the group that includes S. pupula, the generitype.