Valve ultrastructure of Nitzschia shanxiensis nom. nov., stat. nov. and N. tabellaria (Bacillariales, Bacillariophyceae), with comments on their systematic position

Nitzschia shanxiensis nom. nov., stat. nov., described originally from Hunan Province, China as N. sinuata var. constricta Chen & Zhu, was observed from Shanxi and Guizhou Provinces. The morphology of N. shanxiensis is documented by light (LM) and scanning electron microscopy (SEM) and discussed in detail, including a comparison with the other similar species. Nitzschia shhanxiensis has a constricted middle portion of the valve, fibulae crossing about 1/2 of the valve face, and lacks a central nodule. In addition to the new species, N. tabellaria (Grunow) Grunow in Cleve & Grunow was also identified from the same locality, and its valve morphology is also documented with LM and SEM. We comment on other species of diatoms related to N. shanxiensis and N. tabellaria and their relationship to other related genera, including Grunowia and Denticula.