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Pseudostephodinium
From Williams et al., 2017:
[Pseudostephodinium, Yu Jing-xian et al., 1981, p. 262
Type species: Pseudostephodinium sanshuiense, Yu Jing-xian et al., 1981 (pl.1, fig.34)]
Age: Late Cretaceous.
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Original description: [Yu Jing-xian, 1981]: (Translation: Chen et al., 1988, p. 26)
Diagnosis:
Cysts proximate, shape rhomboidal to pentagonal. Periphragm thin and appressed to endophragm, separated only at the apex. Surface ornamented with folds. Epicyst triangular in outline. Apical horn prominent, two antapical horns weakly developed. Paracingulum planar, indicated by ledge-like extension, 5-9 μm wide and reinforced with ribs or folds.
Paratabulation uncertain.
Archeopyle not discernible.
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Chen et al., 1988, p. 26:
From an inspection of the photomicrographs and figures accompanying the description, the basis for several of the characteristics attributed to the genus is not clear. These characteristics include the apical cavation, the antapical horns, and the reinforced, wide cingular structure. Further consideration of the genus is unwarranted until the uncertainties are clarified.
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GSC: (Provisional: courtesy R. Fensome):
Proximate cysts. Outline rhombic to pentagonal to shape of a top with lopped-off bottom. Periphragm thin. Endocyst closely appressed to periphragm. Only on both sides of apex of upper test do periphragm and endophragm appear. Surface has creases. Upper test triangular. Apical horn pronounced. Antapical horns generally undeveloped. Cingulum annular. Surrounding the girdle region is annular wing, 5 - 9 μm wide, with fibrously ramified thickening or creases perpendicular [to] wing annulus. Pressure of wing on periphragm creates a rhombic [frame-like] decorative wrinkling zone surrounding the area outside the apical horn zone. No archaeopyle observed. Tabulation unclear.
Discussion:
With its equatorial wing, annular cingulum. and general lack of antapical horns, this genus resembles Stephodinium but is distinguished from it by the lesser width of the wing annulus and lack of an archaeopyle.
[Pseudostephodinium, Yu Jing-xian et al., 1981, p. 262
Type species: Pseudostephodinium sanshuiense, Yu Jing-xian et al., 1981 (pl.1, fig.34)]
Age: Late Cretaceous.
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Original description: [Yu Jing-xian, 1981]: (Translation: Chen et al., 1988, p. 26)
Diagnosis:
Cysts proximate, shape rhomboidal to pentagonal. Periphragm thin and appressed to endophragm, separated only at the apex. Surface ornamented with folds. Epicyst triangular in outline. Apical horn prominent, two antapical horns weakly developed. Paracingulum planar, indicated by ledge-like extension, 5-9 μm wide and reinforced with ribs or folds.
Paratabulation uncertain.
Archeopyle not discernible.
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Chen et al., 1988, p. 26:
From an inspection of the photomicrographs and figures accompanying the description, the basis for several of the characteristics attributed to the genus is not clear. These characteristics include the apical cavation, the antapical horns, and the reinforced, wide cingular structure. Further consideration of the genus is unwarranted until the uncertainties are clarified.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
GSC: (Provisional: courtesy R. Fensome):
Proximate cysts. Outline rhombic to pentagonal to shape of a top with lopped-off bottom. Periphragm thin. Endocyst closely appressed to periphragm. Only on both sides of apex of upper test do periphragm and endophragm appear. Surface has creases. Upper test triangular. Apical horn pronounced. Antapical horns generally undeveloped. Cingulum annular. Surrounding the girdle region is annular wing, 5 - 9 μm wide, with fibrously ramified thickening or creases perpendicular [to] wing annulus. Pressure of wing on periphragm creates a rhombic [frame-like] decorative wrinkling zone surrounding the area outside the apical horn zone. No archaeopyle observed. Tabulation unclear.
Discussion:
With its equatorial wing, annular cingulum. and general lack of antapical horns, this genus resembles Stephodinium but is distinguished from it by the lesser width of the wing annulus and lack of an archaeopyle.