Brightw. (Brightwell, 1858: 95, fig. 5a, b, d, non 5c)
Rhizosolenia styliformis var. polydactyla van Heurck (1909: 28, figs 66, 67, 70, 71, 74, 75)Rhizosolenia styliformis var. longispina Hust., in Schmidt (1914: 316, figs 5–8, 12); Sundström (1986: 15, figs 5, 47–56); Everitt & Thomas (1986: 5, fig. 2D)Rhizosolenia styliformis f. latissima Brightw., in Peragallo (1892), Manguin (1960: 270, pl. 5, fig. 71; pl. 6, figs 72–75)
Hendey (1937: 320, pl. 11, figs 15–17), Priddle & Fryxell (1985: 94, figs A–G), Priddle et al. (1990: 117, pl. 15.3, fig. 4), Armand & Zielinski (2001; 261, figs 4a, 5A–L, from the holotype slide)
Cells solitary or paired, long, cylindrical. Valves 23–90 µm diameter, markedly asymmetrical, with ventral margin (excluding process) extending for c. half of cell length. Process 30–50 µm long, uniformly tapering; claspers visible. Otaria small, rounded, terminating below process base or extending 1–2 µm along it. Girdle bands in 2 dorsiventral rows, the first 2 bands differing from others due to asymmetry of valves.
Arctic (Priddle et al., 1990); Kerguelen (Hustedt, 1958, as R. styliformis var. longispina); Bellingshausen Sea and Weddell Sea (Ligowski, 1993).
The circumscription of R. styliformis has been the subject of much discussion and revision (e.g. Sundström, 1986; Armand & Zielinski, 2001). Confusion regarding its identification has seen most records of R. styliformis in the pre-2000 literature re-named R. antennata f. semispina, R. polydactyla or R. curvata. However, R. styliformis is distinguishable from these taxa by its otaria ending at or below the process base. Researchers are urged to compare their specimens with recent photographic images of the holotype slide provided by Hasle (1975) and Armand & Zielinski (2001) to ensure correct identification.