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Pseudorhombodinium lisbonense
Pseudorhombodinium lisbonense Wrenn, 1996, p.214,216,218, pl.1, figs.1–4; pl.2, figs.1–5; pl.3, figs.1–4.
Holotype: Wrenn, 1996, pl.3, fig.4.
Age: middle Eocene.
Original description (Wrenn, 1996):
Pseudorhombodinium lisabonense gen. Et. Sp. Nov.
Diagnosis: Dorsoventrally compressed, circumcavate, organic walled peridinioid cyst having a subrhombic to subpentagonal outline, more or less incised parasulcal and paracingular grooves, a distinctive and complex flagellar structure, diminutive antapical horns of nearly equal length, and no paracingular or postcingular horns. Hexa style tabulation is indicated only by the six-sides 2a intercalary archeopyle (Type Ia/Ia). The periarcheopyle is iso-deltaform, the endoarcheopyle is eury-deltaform and both have adcingularly adnate opercula composed of a single paraplate, the 2a.
Shape: The pericyst ouline is subrhombic to subpentagonal in dorsoventral view and sublenticular in polar view. Relatively uncompressed cyst seen in lateral view are ventrally concave and dorsoventrally convex. The pointed apex horn is very short and the truncated antapex of the periphragm gives rise to two short (5-10 µm) antapical horns of nearly equal length. The closely spaced, diminutive antapical horns are separated by the distal end of the parasulcal depression and a small invagination in the antapical outline of the cyst. The endocyst is subpentagonal to subcircular in dorsoventral view and may be somewhat bilobate antapically. No endocysts were observed in polar view.
Phragma: The shagreenate to microgranular perophragm is approximately 1 µm thick and bears nontabular pustules, pits and perforations. The uniformly thick endopragm is thinner (< 0.5 µm) than the periphargm, has a smooth to micrgranular surface and bears circular perforations less than 1 µm in diameter. The cyst is circummcavate in dorsoventral view.
Paratabulation: Neither the pericyst or endocyst exhibit direct evidence of paratabulation other than the archeopyle. The six-sided 2a intercalary archeopyle indicates that the paratabulation is hexa. A very small 3’ paraplate, very narrow 1a and 3a paraplatres and a wide, squat 4’’ paraplate are interpreted from the shape of the periarcheopyle margin. The 3’, 2a, and 4’’ paraplates are stacked.
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Holotype: Wrenn, 1996, pl.3, fig.4.
Age: middle Eocene.
Original description (Wrenn, 1996):
Pseudorhombodinium lisabonense gen. Et. Sp. Nov.
Diagnosis: Dorsoventrally compressed, circumcavate, organic walled peridinioid cyst having a subrhombic to subpentagonal outline, more or less incised parasulcal and paracingular grooves, a distinctive and complex flagellar structure, diminutive antapical horns of nearly equal length, and no paracingular or postcingular horns. Hexa style tabulation is indicated only by the six-sides 2a intercalary archeopyle (Type Ia/Ia). The periarcheopyle is iso-deltaform, the endoarcheopyle is eury-deltaform and both have adcingularly adnate opercula composed of a single paraplate, the 2a.
Shape: The pericyst ouline is subrhombic to subpentagonal in dorsoventral view and sublenticular in polar view. Relatively uncompressed cyst seen in lateral view are ventrally concave and dorsoventrally convex. The pointed apex horn is very short and the truncated antapex of the periphragm gives rise to two short (5-10 µm) antapical horns of nearly equal length. The closely spaced, diminutive antapical horns are separated by the distal end of the parasulcal depression and a small invagination in the antapical outline of the cyst. The endocyst is subpentagonal to subcircular in dorsoventral view and may be somewhat bilobate antapically. No endocysts were observed in polar view.
Phragma: The shagreenate to microgranular perophragm is approximately 1 µm thick and bears nontabular pustules, pits and perforations. The uniformly thick endopragm is thinner (< 0.5 µm) than the periphargm, has a smooth to micrgranular surface and bears circular perforations less than 1 µm in diameter. The cyst is circummcavate in dorsoventral view.
Paratabulation: Neither the pericyst or endocyst exhibit direct evidence of paratabulation other than the archeopyle. The six-sided 2a intercalary archeopyle indicates that the paratabulation is hexa. A very small 3’ paraplate, very narrow 1a and 3a paraplatres and a wide, squat 4’’ paraplate are interpreted from the shape of the periarcheopyle margin. The 3’, 2a, and 4’’ paraplates are stacked.
(...)