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Ctenidodinium scissum
From Fensome et al., 2019:
Ctenidodinium ?scissum McIntyre and Brideaux, 1980, p.21, pl.8, figs.6–9; pl.9, figs.1–6. Holotype: McIntyre and Brideaux, 1980, pl.8, figs.6,8–9. Originally Ctenidodinium, subsequently (and now) Ctenidodinium?. Questionable assignment: Benson (1985, p.152). Age: Valanginian.
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Original diagnosis: McIntyre, 1980, p. 21
Shape: Pericyst - Ambitus subcircular; apical and antapical prominences absent; ambitus of the envelope formed by projecting parasutural crests ovoid to subcircular. Compression slight to moderate dorsoventral. Endocyst - Ambitus subcircular; apical and antapical prominences absent. Slight to moderate dorsoventral compression. Pericoel - Absent.
Phragma: Periphragm - About 0.25 µm thick; surface sculpture scabrate; periphragm forming membranous, finely folded parasutural crests from 10-22 µm high, typically 10-18 µm high, the crests scabrate, weakly striate or wrinkled basally in places, distally entire or weakly crenulated. Endophragm - 0.5-0.75 µm thick; surface sculpture microreticulate, in places granulate or microrugulate.
Paratabulation: Pericyst - Paratabulation of ?4', 6'', ?6c, 5'''-?6''', 1p, 1'''''. Apical paraplate 1' is elongate; of the precingular paraplates, 2''-4'' are largest and polygonal and 6'' is the smallest; of the postcingular paraplates, 2'''-4''' are the largest and are subquadrate to pentagonal; 1p is small relative to 2'''-4''' and is subquadrate. Endocyst - Paratabulation not evident. Pericingulum - Denoted by cingular parasutures of equal width; slightly helicoid, displaced about one-half to one cingulum width (5-7 µm); six? cingular paraplates. Perisulcus - Denoted by low parasutural crests; wider on the hypopericyst, narrowing and extending onto the epipericyst only a short distance, terminated adjacent to the first apical paraplate; sulcal paraplates present but difficult to distinguish.
Archeopyle: Epicystal, Type AP?a(1"-4", 1"-6"). Operculum simple and partially detached or free.
Dimensions: Pericyst length - 51-67 µm, width 50-69 µm.
Variation: Only a few specimens have been found with complete detachment of the operculum. The majority show only partial detachment or an incipient separation along the pericingulum.
Affinities:
McIntyre and Brideaux, 1980, p. 21: Ctenidodinium spissum differs from other species assigned to the genus in possessing entire-margined parasutural crests and a microreticulate endophragm.
Ctenidodinium ?scissum McIntyre and Brideaux, 1980, p.21, pl.8, figs.6–9; pl.9, figs.1–6. Holotype: McIntyre and Brideaux, 1980, pl.8, figs.6,8–9. Originally Ctenidodinium, subsequently (and now) Ctenidodinium?. Questionable assignment: Benson (1985, p.152). Age: Valanginian.
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Original diagnosis: McIntyre, 1980, p. 21
Shape: Pericyst - Ambitus subcircular; apical and antapical prominences absent; ambitus of the envelope formed by projecting parasutural crests ovoid to subcircular. Compression slight to moderate dorsoventral. Endocyst - Ambitus subcircular; apical and antapical prominences absent. Slight to moderate dorsoventral compression. Pericoel - Absent.
Phragma: Periphragm - About 0.25 µm thick; surface sculpture scabrate; periphragm forming membranous, finely folded parasutural crests from 10-22 µm high, typically 10-18 µm high, the crests scabrate, weakly striate or wrinkled basally in places, distally entire or weakly crenulated. Endophragm - 0.5-0.75 µm thick; surface sculpture microreticulate, in places granulate or microrugulate.
Paratabulation: Pericyst - Paratabulation of ?4', 6'', ?6c, 5'''-?6''', 1p, 1'''''. Apical paraplate 1' is elongate; of the precingular paraplates, 2''-4'' are largest and polygonal and 6'' is the smallest; of the postcingular paraplates, 2'''-4''' are the largest and are subquadrate to pentagonal; 1p is small relative to 2'''-4''' and is subquadrate. Endocyst - Paratabulation not evident. Pericingulum - Denoted by cingular parasutures of equal width; slightly helicoid, displaced about one-half to one cingulum width (5-7 µm); six? cingular paraplates. Perisulcus - Denoted by low parasutural crests; wider on the hypopericyst, narrowing and extending onto the epipericyst only a short distance, terminated adjacent to the first apical paraplate; sulcal paraplates present but difficult to distinguish.
Archeopyle: Epicystal, Type AP?a(1"-4", 1"-6"). Operculum simple and partially detached or free.
Dimensions: Pericyst length - 51-67 µm, width 50-69 µm.
Variation: Only a few specimens have been found with complete detachment of the operculum. The majority show only partial detachment or an incipient separation along the pericingulum.
Affinities:
McIntyre and Brideaux, 1980, p. 21: Ctenidodinium spissum differs from other species assigned to the genus in possessing entire-margined parasutural crests and a microreticulate endophragm.