taxonID	type	description	language	source
50A32D8078865F32AC92846E8B398F8E.taxon	description	Figs 5, 6	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
50A32D8078865F32AC92846E8B398F8E.taxon	description	Description. Light microscopy (LM) (Fig. 5 A – P). Valves elliptic-lanceolate with narrowly rostrate to subcapitate apices. Valve dimensions (n = 40): Valve length 17 – 21 µm, width 6.5 – 7.0 µm. Rapheless Valve (Fig. 5 A – H): Axial area narrow, linear, slightly broadened in the middle. A horseshoe-shaped hyaline area present on one side of the central area, containing a cavum. Striae weakly radiate along the valve outline, 13 – 14 in 10 µm (measured opposite the hyaline area). Raphe Valve (Fig. 5 I – P): Axial area narrow, straight, linear. Central area subcircular to rectangular, bordered by 3 – 4 slightly shortened striae on each side. Raphe branches straight, with proximal raphe endings drop-like. Striae radiate along the valve outline, 13 – 14 in 10 µm. Scanning electron microscopy (SEM) (Figs 5 Q, 6 A – C). Rapheless Valve (Figs 5 Q, 6 A): Striae composed of 3 – 4 rows of circular areolae, narrowing near the central area adjacent to the axial area. Striae extend onto the valve mantle. Irregular circular depressions present between the axial area, central area, even between striae. Internally, areolae covered individually, striae wider than virgae and sunken between them. Cavum opening slightly constricted. Raphe Valve (Fig. 6 B, C): Striae composed of 3 – 4 rows of areolae, striae near the central area regularly shortened and narrowing towards the axial area. Striae extend onto the valve mantle. Raphe branches straight, with proximal raphe endings expanding into pores surrounded by drop-like depressions. Distal raphe ends are curved in the same direction, slightly extending onto the valve mantle. Internally, proximal raphe endings slightly deflected to the opposite side, and distal raphe endings terminating in a faint helictoglossa. Internally, areolae covered individually, striae wider than virgae and sunken between them.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
50A32D8078865F32AC92846E8B398F8E.taxon	etymology	Etymology. The species was named for its narrowly rostrate valve apices.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
50A32D8078865F32AC92846E8B398F8E.taxon	distribution	Distribution and ecology. This species has currently only been found at its type locality, where it was collected from floating debris in a pond (water temperature 18.0 ° C, elevation 780 m). The species was observed only in sample (GZ 201510051) at a low relative abundance (0.75 %). In the type material, P. angustirostratum was rare. The associated diatom flora included Sellaphora sp. (15.5 %), Planothidium rostratum (12.5 %), Planothidium liboensis (5.75 %), Fallacia sp. (5.0 %), Achnanthidium minutissimum (5.0 %), Nitzschia palea (5.0 %), and other taxa with lower abundance (less than 5 %) such as Planothidium ellipticum, Sellaphora rotunda, Achnanthidium spp., Punctastriata nyingchiensis, Staurosira construens, Cocconeis placentula, and Platessa hustedtii. Additional ecological information is presented in Table 1.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
233C8D096BE25097A314A5F236BF6C22.taxon	description	Figs 3, 4	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
233C8D096BE25097A314A5F236BF6C22.taxon	description	Description. Light microscopy (LM) (Fig. 3 A – P). Valves elliptical with slightly constricted ends and rostrate extensions. Valve dimensions (n = 75): Length 12 – 18 µm, width 5 – 7 µm. Rapheless Valve (SV) (Fig. 3 A – H): Axial area narrow, straight, linear. Central area with a large, unilateral, horseshoe-shaped hyaline area containing a clearly visible cavum, on the opposite side, striae extend to the axial area. Striae radiate along the valve outline, 15 – 16 in 10 µm (measured opposite the cavum). Raphe Valve (RV) (Fig. 3 I – P): Axial area narrow, straight, and linear, widening slightly towards the central area. Central area irregular, rectangular to slightly rounded, bordered by 2 – 3 shortened, asymmetrical striae on each side. Raphe branches straight, with proximal raphe endings drop-like. Striae radiate along the valve outline, 14 – 17 in 10 µm. Scanning electron microscopy (SEM) (Figs 3 Q, 4 A – C). Rapheless Valve (Figs 3 Q, 4 A): Striae composed of 4 to 5 rows of circular areolae, typically parallel to each other. Near the central area, striae often narrow to 3 areolae adjacent to the axial area. Striae extend onto the valve margin, and no areolae exist on the mantle. The axial area and central area exhibit irregular depressions. The cavum opening is broad, striae are distinctly wider than the virgae and sunken between them, areolae are covered by individual hymenes. Raphe Valve (Fig. 4 B, C): Striae composed of 4 to 5 rows of circular areolae, with some striae consisting of 3 areolae near the axial area and valve margin. Striae extend onto the valve margin, and no areolae exist on the mantle. The central area typically displays 2 to 3 shortened areolae. Raphe branches are straight, with proximal raphe endings expanding into pores, surrounded by shallow, drop-like depressions. Distal raphe ends are curved in the same direction, briefly extending onto the mantle. Internally, proximal raphe endings are slightly deflected to the opposite side, distal raphe endings terminate in a small helictoglossa. The central nodule is raised, striae are markedly wider than the virgae and sunken between them, and areolae are covered by individual hymenes.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
233C8D096BE25097A314A5F236BF6C22.taxon	etymology	Etymology. The species was named for the type locality, Libo County.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
233C8D096BE25097A314A5F236BF6C22.taxon	distribution	Distribution and ecology. This species has currently only been found at its type locality, where it was collected from rocks and floating debris in ponds, as well as from rocks beneath a waterfall (water temperature 18.0 – 19.5 ° C, elevation 629 – 780 m). The species was observed in samples GZ 201510045 (1.0 %), GZ 201510051 (5.8 %), and GZ 201510066 (1.5 %). In the type material (GZ 201510051), P. liboensis exhibited a relatively high abundance. The associated diatom flora included Sellaphora sp. (15.5 %), Planothidium rostratum (12.5 %), Fallacia sp. (5.0 %), Achnanthidium minutissimum (5.0 %), Nitzschia palea (5.0 %), and other taxa with lower abundance (less than 5 %) such as Planothidium ellipticum (Cleve) Round & Bukhtiyarova, Sellaphora rotunda Wetzel, Ector, Van de Vijver, Compère & Mann, Achnanthidium spp., Punctastriata nyingchiensis, Staurosira construens, Cocconeis placentula, and Platessa hustedtii. Additional ecological information is presented in Table 1.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
C92B2E999C1F5D70A6AC6EF828CC24C1.taxon	description	Figs 7, 8	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
C92B2E999C1F5D70A6AC6EF828CC24C1.taxon	description	Description. Light microscopy (LM) (Fig. 7 A – P). Valves elliptical, with rounded ends not extended. Valve dimensions (n = 50): Length 9.5 – 18.0 µm, width 5.5 – 7.5 µm. Rapheless Valve (Fig. 7 A – H): Axial area linear-lanceolate, with central area slightly broadened. One side of the central area has two striae with widened spacing, opposite side striae slightly shortened. Striae weakly radiate along the valve outline, narrowing towards axial area, 10 – 12 in 10 µm (measured opposite hyaline area). Raphe Valve (Fig. 7 I – P): Axial area linear-lanceolate, slightly widened in the central area. Central area subcircular, bordered by 2 – 3 slightly shortened striae on each side. One side of the central area has two striae with widened spacing. Striae radiate weakly, 10 – 12 in 10 µm. Raphe branches straight, occasionally slightly curved. Scanning electron microscopy (SEM) (Figs 7 Q, 8 A – C). Rapheless Valve (Figs 7 Q, 8 A): Striae composed of 4 – 5 rows of circular areolae, markedly narrow near the axial area, reducing to 2 – 3 rows of areolae, striae almost extend onto the valve margin, and some areolae exist on the mantle. Irregular depressions present on the axial area, central area and even on the virgae. Internally, areolae covered. Virgae widen gradually from the ends towards the center, with striae sunken between virgae, a distinctly wider virgae present on one side of the central area (Fig. 8 A, White arrow). Raphe Valve (Fig. 8 B, C): Striae composed of 5 – 6 rows of small circular areolae, markedly narrowing near the central area, reducing to 2 – 3 rows of areolae. striae don’t extend onto the valve margin, and some areolae exist on the mantle (Fig. 8 B, White arrows). Raphe branches straight, occasionally slightly curved. Externally, proximal raphe endings expand into pores, distal raphe ends are curved in the same direction, and extend onto the mantle. Internally, proximal raphe endings slightly deflected to the opposite side, and distal raphe endings terminate in a small helictoglossa. Internally, areolae covered individually by membranes, striae sunken between virgae.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
C92B2E999C1F5D70A6AC6EF828CC24C1.taxon	etymology	Etymology. The species was named for the Maolan Nature Reserve, where the type specimen was collected.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
C92B2E999C1F5D70A6AC6EF828CC24C1.taxon	distribution	Distribution and ecology. This species has currently only been found at its type locality, where it was collected from rocks in a subsurface stream and in rapidly flowing river water (water temperature 18.0 ° C, elevation 650 – 811 m). The species was observed in samples GZ 201510099 (3.75 %), GZ 201510100 (0.25 %), and GZ 2015108 (0.75 %). In the type material (GZ 201510099), P. maolanensis was rare. The associated diatom flora included Cocconeis placentula (23.0 %), Achnanthidium delmontii (7.5 %), Navicula lundii (7.5 %), Navicula antonii Lange-Bertalot, Navicula sp. (6.0 %), Achnanthidium minutissimum (5.5 %), and other taxa with lower abundance (less than 5 %) such as Platessa hustedtii, Achnanthidium spp., Encyonema hophense Krammer, and Achnanthes prominula Levkov & Tofilovska. Additional ecological information is presented in Table 1.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
09DF36F8ECAA562C80062B02ACA36692.taxon	description	Figs 1, 2	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
09DF36F8ECAA562C80062B02ACA36692.taxon	description	Description. Light microscopy (LM) (Fig. 1 A – P). Valves elliptical with slightly constricted ends and rostrate extensions. Valve dimensions (n = 60): Length 11.5 – 19.0 µm, width 5.5 – 7.5 µm. Rapheless Valve (Fig. 1 A – H): Axial area narrow, straight, linear. Central area features a U-shaped hyaline region widening towards the valve margin, on the opposite side, striae extend to the axial area. Striae radiate along the valve outline, 14 – 17 in 10 µm (measured opposite hyaline area). Raphe Valve (Fig. 1 I – P): Axial area narrow, straight, linear. Central area rectangular to nearly circular, bordered by 3 – 4 shortened, asymmetrical striae on each side. Raphe branches straight. Striae radiate along the valve outline, 14 – 18 in 10 µm. Scanning electron microscopy (SEM) (Figs 1 Q, R, 2 A, B). Rapheless Valve (Fig. 1 Q, R): Striae composed of 3 – 4 rows of circular areolae, the outer two rows larger than those near the center. Striae narrow to 2 rows towards the axial area and may expand to 3 – 4 rows near the valve margin, a larger areola marks the end of striae near the valve margin (Fig. 1 Q, white arrow). The central and axial areas feature irregular, shallow, linear depression. Internally, areolae are covered. A clearly visible sinus is present on one side of the central area, forming a shallow circular depression (Fig. 1 R, white arrow). Raphe Valve (Fig. 2 A, B): Striae composed of 3 – 4 rows of circular areolae. Striae narrow towards one end near the axial area. The central area typically displays 2 to 3 shortened striae. Striae almost extend onto the valve margin. Raphe branches are straight, with proximal raphe endings expanding into pores, surrounded by shallow, drop-like depressions. Distal raphe ends are curved in the same direction, briefly extending onto the mantle. Internally, proximal raphe endings are slightly deflected to the opposite side, distal raphe endings terminate in a small helictoglossa. Central nodule is raised, with striae wider raised virgae and sunken between them, and areolae are individually covered.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
09DF36F8ECAA562C80062B02ACA36692.taxon	etymology	Etymology. The species was named for its outline being similar to P. reichardtii.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
09DF36F8ECAA562C80062B02ACA36692.taxon	distribution	Distribution and ecology. This species has currently only been found at its type locality, where it was collected from rocks in a rapid stream (water temperature 18.0 ° C, elevation 780 m). The species was observed in sample GZ 201510041 P (2.0 %), GZ 201510045 (2.5 %). In the type material (GZ 201510045), P. pseudoreichardtii was rare. The associated diatom flora included Navicula lundii Reichardt (19.5 %), Achnanthidium delmontii Pérès, le Cohu & Barthès (12.0 %), Planothidium rostratum (Østrup) Lange-Bertalot (6.0 %), Platessa hustedtii Lange-Bertalot (5.5 %), and Achnanthidium minutissimum (Kützing) Czarnecki (5.0 %), and other taxa with lower abundance (less than 5 %) such as Navicula capitatoradiata Germain, Achnanthidium rivulare Potapova & Ponader, Staurosira construens Ehrenberg, Punctastriata nyingchiensis Luo & Wang, Cocconeis placentula Ehrenberg, and Nitzschia palea Smith. Additional ecological information is presented in Table 1.	en	Li, Yun, Lu, Lin-Xin, Zhou, Hui-Wen, Yu, Pan, Kociolek, John Patrick, Pang, Wan-Ting, Wang, Quan-Xi, You, Qing-Min (2025): Four new Planothidium species (Achnanthidiaceae, Bacillariophyceae) from the Karst region of Guizhou in China. PhytoKeys 259: 81-102, DOI: 10.3897/phytokeys.259.150757
