Planothidium quarnerensis f. rhombica (Giffen) Witkowski & Riaux-Gobin

Joh, Gyeongje, 2021, Distribution and frequent occurrence of diatom taxa (Bacillariophyta) inhabiting warmer oceans in Seogwipo coast of Jeju Island, southernmost Korea, Phytotaxa 517 (1), pp. 1-67 : 25

33. Planothidium quarnerensis f. rhombica (Giffen) Witkowski & Riaux-Gobin ( Figs 89, 90 )

Basionym: Cocconeis quarnerensis f. rhombica Giffen.

Type locality: Mahé Island, Seychelles .

Reference: Riaux-Gobin et al. 2018, p. 117, figs 45–48.

Morphomerics: Valves 13–24 (15–18) μm long, 7–11 (10–11) μm wide, transapical striae 10–11 (8–9) in 10 μm of sternum valve, 11–12 (9) in 10 μm of raphe valve.

Remarks: The structure of vestigial striae is distinct in the axial area of sternum valve. Local specimens are slightly longer, but narrower in width, compared with the type ones. This taxon was reported only from the type locality, Mahé Island of the Seychelles, and probably tropical taxon in warmer coasts. It was rare epiphytes on seaweeds along the Seogwipo coast in Jeju Island, and this is a new report to South Korea.

Figures

FIGURES 78–90. Diatom taxa of Seogwipo coast in Jeju Island (9). Fig. 78. Cocconeiopsis orthoneoides. Fig. 79. Navicula semiarea. Figs 80, 81. Fallacia vittata. Figs 82–84. Cocconeis dirupta var. flexella. Figs 85, 86. Achnanthes citronella. Figs 87, 88. Cocconeis pellucida. Figs 89, 90. Planothidium quarnerensis f. rhombica. Scale bars = 10 μm.