Protoperidinium brevipes (Paulsen) Balech 1974 . Rev. Mus. Argent. Cienc. Nat. “ B. Rivadavia ”, Hydrobiologia 4 (1): 60. (Figs. 3–4, 7) .

References: Lebour 1925: 131, Pl. XXVII, Fig. 2 a–d; Schiller 1937: 200, Fig. 196 a–m; Kiselew 1950: 186, Fig. 310 a– g; Wood 1968: 98, Fig. 287 (as Peridinium brevipes); Konovalova & Selina 2010: 146, Table XIII, 6 a–b, XIX 1–2; Krakhmalny 2011: 191, Table 76, Figs. 5, 9–15;

Basionym: Peridinium brevipes Paulsen 1908 . Nord. Plankton 18: 108, Fig. 151.

Synonyms: Peridinium varicans Paulsen 1911, P. incurvum Lindemann 1924 .

Description: Cells rounded or pentagonal, with a conical epitheca and an apical pore. The epithecal plate pattern comprises seven precingular plates (7ʹʹ), four apical plates (4ʹ), three anterior intercalary plates (3a), 1ʹ plate – “meta”, 2a – “quadra”. The cingulum median, slightly ascending, deep, bordered. The sulcus broadens towards the antapex. The hypotheca with two short antapical spines. Thecal plates littered with microtubercles and pores. Dimensions: 31.7–58.0 μm long and 27.6–52.8 μm wide.

Distribution: Coastal cold-water species (Steidinger & Tangen 1997). Data on the distribution of P. brevipes are given from the GBIF.org (2022) (Fig. 79).