Geiselodinium fibrirugulare (Yu Jingxian et al., 1981) Chen et al., 1988

Now Saeptodinium. Originally Sanshuia, subsequently Geiselodinium, thirdly (and now) Saeptodinium.
Holotype: Yu Jingxian et al., 1981, pl.1, fig.11
Age: Late Cretaceous

Sanshuia fibrirugularis gen. et sp. nov.
Description: Outline broadly elliptical to pentagonal. Strongly protruding side. Periphragm only. Endocyst inconspicuous. Surface of wall has several very slender longitudinal creases. Upper test triangular. Apical horn is sharpened extension of upper test. Apical pore inwardly concave. Lower test subtrapezoidal. Two antapical horns of nearly equal size, about 3.5 µm long. No indication of tabulation. Archaeopyle absent. Cingulum annular or slightly spiralled, about 5 - 6.9 µm wide, decorated on edge with a winding sutural ridge [and opening into a] staggered [pattern] in the ventral region. Sulcus wide, subrhombic with marginal ornamentation of broad ridge whose apex reaches upper test.
Size: Cysts 48.3 - 52.9 µm long and 40 - 43.7 µm wide. Holotype 52.9 x 43.7 µm.

Discussion: This species is distinguished from others in the genus by the several long, slender
longitudinal creases on the surface of the periphragm and by the wide and slightly spiralled cingulum.