Isabeliinium psilatum (Yu Jingxian and Zhang Wangping, 1980) Lentin and Williams, 1985

Originally Deflandrea, subsequently (and now) Isabelidinium.

Holotype: Yu Jingxian and Zhang Wangping, 1980, pl.2, fig.20
Age: Campanian-Early Maastrichtian


Original description Yu Jingxian and Zhang Wangping, 1980 [translation Suning Hou 2025]:

Deflandrea psilata sp. nov.
Holotype: Slide W3–5e, Plate II, Figure 20
Description: The cyst measures 48.3–50.6 µm in length, with the holotype measuring 48.3 µm, and 33–34.5 µm in width, with the holotype measuring 34.5 µm. The central body measures 34.5–39.1 µm in length, with the holotype measuring 39.1 µm, and 28–29.9 µm in width, with the holotype measuring 29.9 µm.
The cyst is dorsoventrally flattened and has a nearly pentagonal outline with thin walls. The apex is small and conical, opening to the exterior at its tip. The two antapical horns are indistinct, with the left one slightly visible and appearing solid.
The central body is ovoid, nearly filling the cyst cavity. It has a cingulum approximately 5.7 µm wide, arranged in a slightly spiral pattern. The surface is smooth, and the archeopyle is intercalary and polygonal in shape
Comparison: The new species has a smooth surface and resembles D. korojonensis Cook & Eis. in shape. However, it is distinguishable by its well-defined cingulum, a central body that nearly fills the entire cyst, and its smaller size.
Stratigraphy: Upper part of the Uytak-Kukbay Formation. 乌依塔克一库克拜组上部。