Indoplatessa Tseplik, Radhakrishnan, Karthick & Kulikovskiy, 2025

Tseplik, Natalia, Radhakrishnan, Cheran, Karthick, Balasubramanian & Kulikovskiy, Maxim, 2025, Indoplatessa gen. nov. - a new monoraphid diatom genus based on Platessa arborea (Achnanthidiaceae, Bacillariophyceae), Phytotaxa 694 (2), pp. 161-172 : 165

Indoplatessa Tseplik, Radhakrishnan, Karthick & Kulikovskiy gen. nov. ( Figs 1–41 )

Type species (here designated): Indoplatessa arborea (C. Radhakrishnan, S. Sherly & B. Karthick) Tseplik, Karthick & Kulikovskiy comb. nov.

Description. LM ( Figs 1–30 ). Frustules monoraphid. Valves elliptic-lanceolate, with rounded apices. Raphe filiform, with straight expanded central ends.Axial area on the raphe valve narrow linear, central area almost rectangular, bordered by 2–3 shortened striae that are frequently more widely spaced. Striae radiate throughout the valve. Axial area on the rapheless valve wide, lanceolate, central area not differentiated. Striae parallel or almost parallel at the centre, radiate towards the apices.

SEM. Raphe valve ( Figs 31–34 , 39, 40 ). Raphe filiform, straight. External central raphe ends straight or almost straight, expanded, positioned in a rounded shallow groove, external distal raphe ends also expanded, slightly bent to one side, located in a shallow groove. Internal central raphe ends strongly hooked to opposite sides, distal ends terminate in well-defined helictoglossae and are bent to the sides opposite the central ends. Striae uniseriate, with a tendency to become biseriate near the valve apices. Areolae slit-like, transapically elongated throughout the valve, round only at the central part of the valve near the axial area, covered internally with hymenes. Interstriae wider than the striae, slightly raised internally.

Rapheless valve ( Figs 35–38 , 41 ). Externally, axial area covered with irregular depressions. Striae uniseriate with a tendency to become biseriate throughout the valve, with mostly slit-like, transapically elongated areolae. Width of striae varies, the interstriae are still generally wider than the striae. Interstriae are slightly raised both externally and internally.

Type locality: Tree bark moss from Sikkim, India (27.34829°N, 88.19187°E; elevation 1794 m a.s.l.) .

Etymology: The initial designation of the genus ( Platessa ) was amalgamated with the root Indo -, signifying India.

New combination: Indoplatessa arborea (C. Radhakrishnan, S. Sherly & B. Karthick) Tseplik, Radhakrishnan, Karthick & Kulikovskiy comb. nov.

Basionym: Platessa arborea C. Radhakrishnan, S. Sherly & B. Karthick in Sherly et al. 2022. Platessa arborea sp. nov. ( Bacillariophyceae ): A new tree moss dwelling diatom from the Eastern Himalayas, India. Phytotaxa 552(2): 152, figs 1–67.

Figures

FIGURES 1–30. Indoplatessa arborea comb. nov. Slide no. 58–55, sample no. AHMA #2878. LM, DIC. Figs 1–15. Raphe valves. Figs 16–30. Rapheless valves. Scale bar = 10 μm.

FIGURES 31–34. Indoplatessa arborea comb. nov. Sample no. AHMA #2878. SEM, raphe valves. Figs 31–32. External view. Figs 33–34. Internal view. Scale bars = 1 μm.

FIGURES 35–38. Indoplatessa arborea comb. nov. Sample no. AHMA #2878. SEM, rapheless valves. Figs 35–36. External view. Figs 37–38. Internal view. Scale bars = 1 μm.

FIGURES 39–41. Indoplatessa arborea comb. nov. Sample no.AHMA #2878. SEM. Fig. 39. Partial external view of the raphe valve. Fig. 40. Partial internal view of the raphe valve. Fig. 41. Partial external view of the rapheless valve. Scale bars = 1 μm.