Hantzschia minima M.Rybak sp. nov. (Figs 1–15, 46–52) LM observations (Figs 1–15): — Valves dorsiventral with straight or almost straight dorsal margin. Ventral margin weakly concave in middle, becoming slightly convex near apices.Apices abruptly protracted, small and clearly capitate, slightly deflected towards dorsal side. Valve dimensions (n=20): length 17.5–38.5 μm, width 3.5–4.5 μm. Fibulae 5–8 in 10 μm, unequally spaced, middle two fibulae clearly more distant. Striae equidistant, weakly radiate in middle, 22–25 in 10 μm. In some specimens, striae in valve middle slightly more spaced than others (Figs 10, 14). Areolae not discernible. SEM observations (Figs 46–52): — Valves on the ventral side bordered by a clearly thickened keel (Figs 46, 47). Striae composed of round areolae occluded by individual hymens. 49–60 in 10 µm (Figs 47, 51). External central raphe endings slightly deflected, very close together (Fig. 51). Distal raphe endings clearly hooked (Fig. 49). Internally central raphe endings deflected to opposite directions (Fig. 52). Striae forming narrow, deep, parallel grooves (Figs 48, 52). Each fibulae connected to 1–4 transapically costae (Fig. 48). Type:— Indonesia, Kairatu, West Seram, Molouki, 3°21’46.5”S 128°22’19.48”E, coll. date. 28 June 2018, holoslide no. SZCZ28484! and the unmounted material with the same number at the Szczecin Diatom Collection (University of Szczecin, Poland), iso - slide no. 2018/445 and the unmounted material with the same number at the University of Rzeszów, Poland. The type population is illustrated on Figs 1–15 and 46–52. Etymology:— The species epithet “ minima ” refers to its small size. Hantzschia minima sp. nov. is one of the smallest species in the genus. Distribution:— So far, the species was only observed from the type locality. Associated diatom flora:— The most abundant taxa in assemblage were: Hantzschia minima sp. nov., Humidophila contenta (Grunow) Lowe, Kociolek, Johansen, Van de Vijver, Lange-Bertalot & Kopalová (2014: 357), H. lacunosa (Moser, Lange-Bertalot & Metzeltin) Lowe et al. (2014: 358), Luticola intermedia (Hustedt) Levkov, Metzeltin & Pavlov (2013: 138), L. sublagerheimii Levkov, Metzeltin & Pavlov (2013: 229) and Pinnularia borealis Ehrenberg (1843: 420). The share of Hantzschia tokarczukiana sp. nov. did not exceed 5% in the assemblages.

Published as part of Mateusz, Rybak, Natalia, Kochman-Kędziora & Muzaky, Luthfi Oktiyas, 2022, Four novel species from the genus Hantzschia Grunow (Bacillariophyta: Bacillariaceae) from rural areas of Southeast Asia, pp. 207-221 in Phytotaxa 567 (3) on pages 209-212, DOI: 10.11646/phytotaxa.567.3.1, http://zenodo.org/record/7156659