Pterocystis pontica Prokina, Zagumyonnyia and Mylnikova, 2019
Diagnosis: Spine- and plate-scales were found. Spine-scales are 3.25-4.72 μm in length, with hollow shaft and flattened round basal membrane, 0.55-1.13 μm in diameter. Membrane is stretched along a shaft, parallel to a longitudinal axis of scales and with dense margin. Plate-scales ovoid in shape, 1.8-2.4 × 0.9-1.3 μm, with axial rib (1.24-1.71 μm in length), slightly shifted toward the narrowed end of scales. Hollow shaft of spine scales is 3.25-4.72 μm in length, 0.11-0.15 μm in diameter, slightly curved in arc. Round flattened distal tip truncated (or broken off) on some scales.
Ecology: Marine, Black Sea.
Remarks: This species is related to the genus Pterocystis due to the correspondence with the genus diagnosis: (1) oval plate scales with axial rib; (2) spine scales with basal membrane; (3) hollow shaft curved dorsally; (4) absence of a clear boundary between basal and lateral wings of basal membrane. Pterocystis pontica differs from P. anapoda Siemensma et Roijackers, 1988 and P. paliformis (Dürrschmidt, 1987) Siemensma, 1991 by the absence of elongated basal membrane and larger size of basal membrane relative to the length of a shaft; from P. pyriformis (Dürrschmidt, 1987) Siemensma, 1991 by the absence of pear-shaped basal membrane, and lateral wings extending along almost the entire length of a shaft; from P. canadensis Cavalier-Smith et Von der Heyden, 2007 and P. pinnata (Nicholls, 1983) Siemensma et Roijackers, 1988 by the absence of well marked basal wing, and lateral wings extending along almost the entire length of shaft.