Apteodinium helicoides, He Chengquan, 1991

Holotype: He Chengquan, 1991, pl.3, fig.22
Location and stratigraphy: Shache County Altashi, Wulagen fm; Wuqia county Basebulak, Wulagen fm and Basebulak fm member two, three.
Age: Middle-Late Eocene

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

Description:
Cyst oval - long oval, wide waist, divided into nearly equal large two parts by the cingulum. Upper cyst bell, with a distinct apical horn, conical, length 6-7.5μm, the top is blunt or wide; Lower cyst semicircle- high arched, lacking antapical horns.
The cingulum is at the equatorial position, distinct, shallow concave, spiral, 4-7.5 μm wide, the margin of which is decorated with smooth ridges; The ends are staggered about 2-3 times width of the cingulum on the ventral side.
Lack of sulcus.
Thin wall, the surface is fine granular or weak wrinkle-like, contour smooth, with a few longitudinal linear grooves.
The archeopyle is precingular, P-type, outline nearly the horseshoe-shaped, formed by the third precingular plate missing. This operculum is off or in situ preserved.
The cyst may contain yellow-green nuclear.

Dimension:
The cyst length 62.5-85μm, width 42.5-75μm (measured 6), the holotype length 85μm, width 57μm, the apical horn length of 7.5μm, cingulum width 5μm.

Affinities/Comparison:
This species is different from Apteodinium tenuicinctum in spiral and shallow concave cingulum.