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Millioudodinium spinoreticulatum
Millioudodinium spinoreticulatum McIntyre and Brideaux, 1980
Now Cribroperidinium. Originally Millioudodinium, subsequently Apteodinium, thirdly (and now) Cribroperidinium.
Taxonomic junior synonym: Gonyaulacysta (as Apteodinium) compta, according to Lucas-Clark (1987, p.178).
Holotype: McIntyre and Brideaux, 1980, pl.3, figs.4,9,12; Jan du Chêne et al., 1986, pl.13, figs.9-11
Locus typicus: "Grizzly Gorge", District of Mackenzie, Canada
Stratum typicum: Valanginian
Original diagnosis: McIntyre and Brideaux, 1980, p.15-16
Shape: Pericyst - Ambitus ovoid to rounded-pentagonal, longer than broad; apical horn, 7-16 Ám in length, with a distal notched cap. Dorsoventral compression.
Endocyst - Commonly present, but difficult to delineate; everywhere closely appressed to the pericyst; apical horn as for pericyst; dorsoventral compression.
Pericoels - absent.
Phragma: Periphragm - 0.5-1.0 Ám thick; surface sculpture consists of parasutural ridges together with an irregularly anastomosing or more regular system of low ridges which may form an imperfect to perfect reticulum; ridges less than 0.5 Ám high and less than 0.25 Ám wide; bearing spines, from 1.0-2.0 Ám high (typically about 1.0 Ám) distributed randomly on the ridges and on more prominent parasutural ridges. Endophragm - Less than 0.5 Ám thick, commonly obscure; presumably smooth.
Paratabulation: Pericyst - Parasutural ridges denote a paratabulation determined approximately as 4", ?6", ?6c, ?6""", ?1p, 1"""". Parasutural ridges are obscured in places by the intratabular reticulum. Endocyst - Paratabulation not observed.
Pericingulum - Present, distinct, slightly indented, helicoid; with ?six cingular paraplates. Perisulcus - Present as a shallow depression, the details difficult to delineate; narrow anteriorly, widest posteriorly; extending about one-third of the way up the epipericyst. Archeopyle. Precingular, Type P(3"). Operculum free, simple, longer than broad, strongly rounded, gibbous-shaped.
Variation: The degree of reticulation is more or less constant for a given specimen, but varies widely between specimens; in places on a given specimen, the spines may be discrete.
Dimensions: Pericyst length 70-87 µm, width 55-70 µm.
Affinites:
McIntyre and Brideaux, 1980, p. 16: The intratabular spine-bearing network of low ridges distinguishes this species from other similar species of Millloudodinium.
Now Cribroperidinium. Originally Millioudodinium, subsequently Apteodinium, thirdly (and now) Cribroperidinium.
Taxonomic junior synonym: Gonyaulacysta (as Apteodinium) compta, according to Lucas-Clark (1987, p.178).
Holotype: McIntyre and Brideaux, 1980, pl.3, figs.4,9,12; Jan du Chêne et al., 1986, pl.13, figs.9-11
Locus typicus: "Grizzly Gorge", District of Mackenzie, Canada
Stratum typicum: Valanginian
Original diagnosis: McIntyre and Brideaux, 1980, p.15-16
Shape: Pericyst - Ambitus ovoid to rounded-pentagonal, longer than broad; apical horn, 7-16 Ám in length, with a distal notched cap. Dorsoventral compression.
Endocyst - Commonly present, but difficult to delineate; everywhere closely appressed to the pericyst; apical horn as for pericyst; dorsoventral compression.
Pericoels - absent.
Phragma: Periphragm - 0.5-1.0 Ám thick; surface sculpture consists of parasutural ridges together with an irregularly anastomosing or more regular system of low ridges which may form an imperfect to perfect reticulum; ridges less than 0.5 Ám high and less than 0.25 Ám wide; bearing spines, from 1.0-2.0 Ám high (typically about 1.0 Ám) distributed randomly on the ridges and on more prominent parasutural ridges. Endophragm - Less than 0.5 Ám thick, commonly obscure; presumably smooth.
Paratabulation: Pericyst - Parasutural ridges denote a paratabulation determined approximately as 4", ?6", ?6c, ?6""", ?1p, 1"""". Parasutural ridges are obscured in places by the intratabular reticulum. Endocyst - Paratabulation not observed.
Pericingulum - Present, distinct, slightly indented, helicoid; with ?six cingular paraplates. Perisulcus - Present as a shallow depression, the details difficult to delineate; narrow anteriorly, widest posteriorly; extending about one-third of the way up the epipericyst. Archeopyle. Precingular, Type P(3"). Operculum free, simple, longer than broad, strongly rounded, gibbous-shaped.
Variation: The degree of reticulation is more or less constant for a given specimen, but varies widely between specimens; in places on a given specimen, the spines may be discrete.
Dimensions: Pericyst length 70-87 µm, width 55-70 µm.
Affinites:
McIntyre and Brideaux, 1980, p. 16: The intratabular spine-bearing network of low ridges distinguishes this species from other similar species of Millloudodinium.