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Dimidiadinium
From Williams et al., 2017:
[Dimidiadinium, Brideaux, 1977, p. 37
Type species: as Gonyaulacysta dangeardii, Sarjeant, 1968 (pl.3, fig.8; text-fig.3)] ; Dimidadinium dangeardii, Brideaux, 1977
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Original description: [Brideaux, 1977]:
Shape:
Pericyst ambitus elongate, the length up to twice the width; main portion of the ambitus rounded and subrhombic; epipericyst prolonged to form an apical horn or prominence; hypopericyst tapering gently then more sharply posteriorly and forming a frustum, subquadrate to quadrate in plan; hypopericyst open antapically forming an antapical breach, or closed. Endocyst ambitus subcircular to ovoid to subrhombic, slightly elongate, rounded apically or produced to form a small apical prominence. A distinct apical pericoel not present; antapical pericoel formed by separation of the hypopericyst and hypoendocyst; ambital pericoel not developed; slight dorso-ventral compression.
Phragma: Periphragm smooth or with minor surface ornamentation; of constant thickness; produced to form smooth or variably ornamented parasutural ridges, the ornament varying from small spines to large spines of variable length, or trifurcate spines, the ornament intergonal and/or gonal in position. Endocyst smooth or with minor sculpture and of constant thickness.
Paratabulation: Paratabulation denoted by smooth to ornamented parasutural ridges and determined as 4`, ?a, 6", 6c, 5```-?6```, 0-1 p, 1````. Evidence of paratabulation not observed on the endocyst.
Archeopyle/operculum: Periarcheopyle formed by the loss of the third precingular paraplate; perioperculum simple, detached, somewhat gibbous to hoof-shaped. Endoarcheopyle and endoperculum similar. Formula: P/P.
Pericingulum/perisulcus: Pericingulum slightly to moderately helicoid, denoted by smooth or ornamented parasutures which delineate six cingular paraplates. Perisulcus present; generally narrower anteriorly and terminating adjacent to the first apical paraplate, slightly to distinctly broader posteriorly, terminating adjacent to the antapical paraplate or antapical breach; laterally delineated by smooth or spiny parasutures; perisulcal region slightly to moderately depressed relative to the rest of the pericyst outline.
[Dimidiadinium, Brideaux, 1977, p. 37
Type species: as Gonyaulacysta dangeardii, Sarjeant, 1968 (pl.3, fig.8; text-fig.3)] ; Dimidadinium dangeardii, Brideaux, 1977
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Brideaux, 1977]:
Shape:
Pericyst ambitus elongate, the length up to twice the width; main portion of the ambitus rounded and subrhombic; epipericyst prolonged to form an apical horn or prominence; hypopericyst tapering gently then more sharply posteriorly and forming a frustum, subquadrate to quadrate in plan; hypopericyst open antapically forming an antapical breach, or closed. Endocyst ambitus subcircular to ovoid to subrhombic, slightly elongate, rounded apically or produced to form a small apical prominence. A distinct apical pericoel not present; antapical pericoel formed by separation of the hypopericyst and hypoendocyst; ambital pericoel not developed; slight dorso-ventral compression.
Phragma: Periphragm smooth or with minor surface ornamentation; of constant thickness; produced to form smooth or variably ornamented parasutural ridges, the ornament varying from small spines to large spines of variable length, or trifurcate spines, the ornament intergonal and/or gonal in position. Endocyst smooth or with minor sculpture and of constant thickness.
Paratabulation: Paratabulation denoted by smooth to ornamented parasutural ridges and determined as 4`, ?a, 6", 6c, 5```-?6```, 0-1 p, 1````. Evidence of paratabulation not observed on the endocyst.
Archeopyle/operculum: Periarcheopyle formed by the loss of the third precingular paraplate; perioperculum simple, detached, somewhat gibbous to hoof-shaped. Endoarcheopyle and endoperculum similar. Formula: P/P.
Pericingulum/perisulcus: Pericingulum slightly to moderately helicoid, denoted by smooth or ornamented parasutures which delineate six cingular paraplates. Perisulcus present; generally narrower anteriorly and terminating adjacent to the first apical paraplate, slightly to distinctly broader posteriorly, terminating adjacent to the antapical paraplate or antapical breach; laterally delineated by smooth or spiny parasutures; perisulcal region slightly to moderately depressed relative to the rest of the pericyst outline.