Two new Stephanodiscaceae species (Bacillariophyta) from SW China

Two new freshwater centric diatom species were described from the southwest of China based on light and scanning electron microscopy. Pliocaenicus weixiense sp. nov. has a transversely undulate valve face, marginal fultoportulae situated at the end of the hyaline strips, central fultoportulae forming a ring positioned in a circular pattern, each with 3–4 (usually 3) satellite pores, and a single rimoportula located at the base of the inner distal end of the costa. Tertiarius aspera sp. nov. has an uneven valve face with small granules that may be present on the marginal area and valve mantle, marginal fultoportulae situated on each costa close to the margin of the valve, 6–7 central fultoportulae forming a ring near the valve center each with two satellite pores, and one rimoportula located on the valve face/mantle junction in the middle of costa on the internal valve. T. aspera sp. nov. is the first reported extant species in the genus. This study played an important role in studying the taxonomic status and ecological information of the genus, and the establishment of the two new taxa will help demonstrate the unique nature of freshwater diatom flora in the southwest of China.