Hantzschia subrobusta, You & Kociolek, 2015

You, Qingmin, Kociolek, John Patrick & Wang, Quanxi, 2015, The diatom genus Hantzschia (Bacillariophyta) in Xinjiang Province, China, Phytotaxa 197 (1), pp. 1-14 : 8-9

Hantzschia subrobusta Q-M You & J. P. Kociolek, sp. nov. (Figs 40–46; figure 42 = holotype)

Valves distinctly asymmetrical to the apical axis. Ventral margins obviously concave at center, slightly convex at poles. Dorsal margins smoothly convex throughout with similar angles of bend at ventral margins along most of valve except poles. Ends protracted, narrowly-rostrate. Length 165–205 μm, breadth 12–14 μm. Fibulae, 4–6 in 10 μm, not equidistant, the median two are more distant than the others, each of them mostly connected with 1–2, rarely 3–5, transapical costae. External raphe branches continuous in the valve middle (Fig. 45), undetected internally with SEM. Striae parallel throughout, 14–17 in 10 μm. Striae puncta not discernible in LM. In SEM puncta appear as small, rounded poroids (Figs 44–46), c. 30–38 in 10 μm, extending from one margin to the other even at the fibulae (Fig. 45).

Type:— CHINA. Chabuchaer. ( SHTU, slide XJ-010181! Holotype illustrated in figure 42)

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Etymology:— The specific epithet reflects its similarity to H. amphioxys var. robusta Østrup.

Distribution and ecology:— Yili River, Chabuchaer, Xinjiang, China. Altitude 600m, pH 8.2, collected in the wetland near the Yili River.

Observations:— This is a rare taxon. It is most similar to H. amphioxys var. robusta Østrup (1910: 249) , while there are differences relative to the valve dimensions and number of costae connected fibula. Specimens from Xinjiang are relatively shorter and narrower when compared to specimens from European populations. Moreover, Xinjiang’s specimens are similar to H. alkaliphila ( Lange-Bertalot et al. 2003) , but the two differ mainly in outline, valve breadth and interior striae arrangement near the fibulae ( Table 4).