Pterocystis foliacea ( Dürrschmidt, 1985 ) Siemensma, 1991

Prokina, Kristina I., Zagumyonnyi, Dmitry G. & Tikhonenkov, Denis V., 2018, Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe, Acta Protozoologica 57 (4), pp. 243-266 : 257-258

Pterocystis foliacea ( Dürrschmidt, 1985) Siemensma, 1991 [bas.: Acanthocystis foliacea Dürrschmidt, 1985 ] ( Fig. 5I–L)

Description: Spine scales leaf-shaped, consist of a hollow cylindrical shaft, lateral and basal wings. Wings connect to each other perpendicularly, forming subapical protrusion. Shaft is 2.49–6.02 µm in length, 0.15–0.20 µm in diameter. Lateral wings are 2.11– 2.58 µm in width, slightly narrowed to truncated tips (0.24–0.46 µm in width). Oval plate scales are 3.67– 4.39×1.92–2.63 µm, with medial thickening and dense margins.

Remarks: Morphology of observed scales corresponds to previous descriptions, however, many authors described smaller plate scales (2.5–3.1×1.4–2.0 µm) ( Dürrschmidt 1985, 1987b; Gaponova 2008; Plotnikov and Gerasimova, 2017; Prokina and Mylnikov 2019).

Distribution: Freshwaters of Europe ( Gaponova 2008), Asia ( Wujek and Saha 2006), Australia (Croome 1987), Africa ( Wujek and Ogundipe 2002), S. America ( Dürrschmidt 1985, 1987b; Prokina and Mylnikov 2019), Japan, New Zealand, Sri Lanka ( Dürrschmidt 1987b). It was found in Russia in freshwaters of Orenburg Region ( Ermolenko and Plotnikov 2013), in saline inland waters of Volgograd Region ( Plotnikov and Gerasimova 2017), in the Black Sea (unpubl. data).