Apteodinium subtile, He Chengquan, 1991

Holotype: He Chengquan, 1991, pl.3, fig.8
Location and stratigraphy: Wuqia County Basebulak; Wulagen fm.
Age: Middle Eocene

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Original description: [He Chengquan, 1991]: (translated by Suning Hou, 07-01-2019):

Description:
Cyst outline taro-shaped, the body sub-circular-oval, the upper and lower cysts nearly equal or epicyst larger, with an apical horn, usually conical or papillary, 2.5-10 μm long; Hypocyst semi circular, no antapical horns.
Cingulum near equator, clear or obtuse, annular, 5-7.5 μm wide, not concave at sides of cyst, with fine ridges on edges; Cingulum may become blurred if specimens are eroded.
Lack of sulcus.
Thin wall, the surface of granular, usually corroded rough pit-shaped -irregular reticular wrinkles, contour granular - nearly smooth.
Archeopyle precingular, P-type, outline trapezoid, formed by the third precingular plate movement. Operculum shedding or adhering to the side of the cyst (the cyst is often laterally pressed.)

Dimensions:
Cyst length 60-77.5 μm, width 60-75 μm (measured 9); Holotype width 55 μm, apical horn length about 3.5 μm.