Minidiscus proschkinae (Makarova) J. S. Park & J. H. LeeThalassiosira proschkinae Makarova et al. (1979): 922, pl. 1, figs. 1–7 — Snoeijs (1993): 113, pl. 99; Hasle and Syvertsen (1997): 84, table 14, pl. 13; Hoppenrath et al. (2007): 59, fig. 24 e.Minidiscus proschkinae — Park et al. (2017); Li et al. (2020); Guiry and Guiry (2025).DescriptionForms chains of 2–3 cells, linked by mucilage thread extruded from central fultoportula. Cells circular with flattened valve face or slightly convex, with sharp-angled mantle. Diameter 11.7 (3–11.5) µm. Single rimoportula located on valve surface adjacent to central fultoportula, both without external tubes and with a single areola in between. Areolae in tangential rows, 30–35 (25–30) in 10 μm, at valve centre. Marginal fultoportula processes (MFPs), without external tubes, 6 (6–8) closely spaced, 5 (1.24–1.91 µm) separation, processes 2.75 in 10 µm.DiagnosisThe external rimoportula and central fultoportula, both without external tubes and close together, the MFPs without external tubes and the unique ornamentation of the valve surface place this specimen in Minidiscus proschkinae. Our molecular data from Trincomali Channel and plankton from Miners Bay Wharf, Mayne Island, support the presence of Minidiscus proschkinae.NotesPreviously identified in Haida Gwaii, BC, by Pienitz et al. (2003). iNaturalist ID: 260112129 (Fig. 27).