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Valvaeodinium diacrorhaetium
Valvaeodinium diacrorhaetium (Morbey, 1975) Lentin and Williams, 1989
Originally Comparodinium, subsequently (and now) Valvaeodinium.
Taxonomic senior synonym: Comparodinium (as and now Valvaeodinium) koessenium, according to Below (1987b, p.66).
Holotype: Morbey, 1975, pl.16, figs.3-6; text-fig.20a
Locus typicus: Westbury Member, Rhaetic Formation, Bunny Hill Borehole, Notts., England
Stratum typicum: Rhaetian
Original diagnosis: Morbey, 1975, p.44: Comparodinium diacrorhaetium
Cyst chorate, marginate; spheroidal, cylindroidal, ovoidal in shape. Wall thin, smooth or microgranulate. Tabulation indeterminate, vaguely by intratabular and/or plate-bounding processes. Processes tractal in development, simple or compound heteromorphic, hollow, possibly open distally, equal/unequal in length, 16-25 % cyst length in length, 6-8 (rarely 4-9) in number per tract. Process bases slightly constricted, angular or sharply curved; stems tapered, conical or cylindrical; terminations generally bifurcate, occasionally simple with truncate tips. Cingulum reflected by unornamented equatorial region. Sulcus not evident. Archeopyle apical.
Dimensions: Cyst length 14 (19) 24 µm (10 specimens measured). Cyst length: breadth 2:1--6:5. Process length ca. 2-5 µm, diameter ca. 1-2.5 µm.
Remarks: Transverse ribbon-like folds may define the apical archeopyle suture line. The process cavity-cyst cavity relationship is indeterminate. The few simple process terminations may well represent preservational features. The type species Comparodinium koessenium. differs in its larger size, more numerous processes and more distinctive reflected cingulum.
Originally Comparodinium, subsequently (and now) Valvaeodinium.
Taxonomic senior synonym: Comparodinium (as and now Valvaeodinium) koessenium, according to Below (1987b, p.66).
Holotype: Morbey, 1975, pl.16, figs.3-6; text-fig.20a
Locus typicus: Westbury Member, Rhaetic Formation, Bunny Hill Borehole, Notts., England
Stratum typicum: Rhaetian
Original diagnosis: Morbey, 1975, p.44: Comparodinium diacrorhaetium
Cyst chorate, marginate; spheroidal, cylindroidal, ovoidal in shape. Wall thin, smooth or microgranulate. Tabulation indeterminate, vaguely by intratabular and/or plate-bounding processes. Processes tractal in development, simple or compound heteromorphic, hollow, possibly open distally, equal/unequal in length, 16-25 % cyst length in length, 6-8 (rarely 4-9) in number per tract. Process bases slightly constricted, angular or sharply curved; stems tapered, conical or cylindrical; terminations generally bifurcate, occasionally simple with truncate tips. Cingulum reflected by unornamented equatorial region. Sulcus not evident. Archeopyle apical.
Dimensions: Cyst length 14 (19) 24 µm (10 specimens measured). Cyst length: breadth 2:1--6:5. Process length ca. 2-5 µm, diameter ca. 1-2.5 µm.
Remarks: Transverse ribbon-like folds may define the apical archeopyle suture line. The process cavity-cyst cavity relationship is indeterminate. The few simple process terminations may well represent preservational features. The type species Comparodinium koessenium. differs in its larger size, more numerous processes and more distinctive reflected cingulum.