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Microdinium dentatum
Microdinium dentatum Vozzhennikova 1967; Emendations: Fechner, 1985, p.120; Lentin and Vozzhennikova, 1990, p.104–105, both as Microdinium dentatum; Below, 1987b, p.45–46, as Phanerodinium dentatum.
Originally (and now) Microdinium, subsequently Microdinium?, thirdly Phanerodinium.
Stover and Evitt, 1978, considered this to be a provisionally accepted species of Microdinium. Lentin and Vozzhennikova, 1990, included the species in Microdinium without question.
Below, 1987, transferred this species to Phanerodinium Deflandre, 1937. Lentin and Williams, 1989, retained the species in Microdinium.
Holotype: Vozzhennikova, 1967, pl.38, figs.2a-e; Lentin and Vozzhennikova, 1990, pl.12, figs.5-7; text-fig.59
Locus typicus: Smolensk region, Russia
Stratum typicum: Late Cretaceous
Translation Vozzhennikova, 1967: Lees in Sarjeant (ed.) 1971, p. 144
Original diagnosis: Vozzhennikova 1967, p. 94-95
Theca spherical or ovoid. Epitheca smaller than hypotheca. Arrangement of plates as in Microdinium ornatum. Plates and margins of transverse furrow bounded by light coloured toothed crest. Theca pale yellow in colour, the surface granular.
Dimensions: Length: 32.4-40.5 Ám; Breadth: 32.4-37 Ám; Width of transverse furrow: 5.4 Ám; Width of crest: 4-5 Ám.
Emended descripition: Lentin and Vozzhennikova, 1990, p.105
Cyst shape roundly oval; proximochorate with broad, castellated suturocavate crests, dominantly on the large hypocyst, epicyst less than 1/3 the length of hypocyst; parasutures wide, suturocavate with distinctly castellate margins, less pronounced on the epicyst; periphragm ornanented with intratabular granules; paratabulation outlined by large suturocavate crests on the hypocyst and small delicate crests on the epicyst; formula 4", 6"", 6c, 6""", 1p, 1"""". Archeopyle apical, operculun adnate; paracingulum bounded on both anterior and posterior margins with castellated suturocavate crests; parasulcus tear-drop shaped bounded by castellated suturocavate crests.
Size: Holotype length 40 Ám, width 37 Ám, width of paracingulum about 5 Ám, width of parasutural septa about 4 Ám. Range, length 32-40 Ám, width 32-37 Ám.
Emended description: Fechner, 1985, p.120-121
The small cyst shows a more or less ellipsoidal outline. The epicyst is distinctly smaller than the hypocyst. An apical archeopyle is commonly developed. The denticulate crests marking the paratabulation, are distinctly higher on the hypocyst than on the epicyst. The parasulcus widens toward the antapex and borders upon the single antapical paraplate. The surface of the paraplates is slightly granular or scattered with tiny tubercles. Despite the absence of the operculum, including an unknown number of apical and intercalary paraplates, the following paratabulation formula is developed: (?"), (?a), 6", 6c, 6""", 1p, 1"""", 4s. The pictured cyst has a breadth of 25 Ám and a length of 30 Ám (without operculum).
Affinities:
Vozzhennikova 1967, p. 94-95: Microdinium dentatum differs from related forms in having a toothed crest on the boundaries of the plates and on the margin of the transverse furrow. Note: Some members of this species have a different shape of theca: in some it is ovoid, in others spherical. This is the basis for the separation of two forms: f. dentatum and f. sphaericum.
Fechner, 1985, p. 121: M. dentatum differs from M. setosum and M. irregulare in having denticulate parasutural crests, rather than rows of spines or undifferentiated septae. Because of the insufficient description and the obscure figures by Vozzhennikova 1967, both subspecies dentatum and sphaericum must be considered superfluous.
Originally (and now) Microdinium, subsequently Microdinium?, thirdly Phanerodinium.
Stover and Evitt, 1978, considered this to be a provisionally accepted species of Microdinium. Lentin and Vozzhennikova, 1990, included the species in Microdinium without question.
Below, 1987, transferred this species to Phanerodinium Deflandre, 1937. Lentin and Williams, 1989, retained the species in Microdinium.
Holotype: Vozzhennikova, 1967, pl.38, figs.2a-e; Lentin and Vozzhennikova, 1990, pl.12, figs.5-7; text-fig.59
Locus typicus: Smolensk region, Russia
Stratum typicum: Late Cretaceous
Translation Vozzhennikova, 1967: Lees in Sarjeant (ed.) 1971, p. 144
Original diagnosis: Vozzhennikova 1967, p. 94-95
Theca spherical or ovoid. Epitheca smaller than hypotheca. Arrangement of plates as in Microdinium ornatum. Plates and margins of transverse furrow bounded by light coloured toothed crest. Theca pale yellow in colour, the surface granular.
Dimensions: Length: 32.4-40.5 Ám; Breadth: 32.4-37 Ám; Width of transverse furrow: 5.4 Ám; Width of crest: 4-5 Ám.
Emended descripition: Lentin and Vozzhennikova, 1990, p.105
Cyst shape roundly oval; proximochorate with broad, castellated suturocavate crests, dominantly on the large hypocyst, epicyst less than 1/3 the length of hypocyst; parasutures wide, suturocavate with distinctly castellate margins, less pronounced on the epicyst; periphragm ornanented with intratabular granules; paratabulation outlined by large suturocavate crests on the hypocyst and small delicate crests on the epicyst; formula 4", 6"", 6c, 6""", 1p, 1"""". Archeopyle apical, operculun adnate; paracingulum bounded on both anterior and posterior margins with castellated suturocavate crests; parasulcus tear-drop shaped bounded by castellated suturocavate crests.
Size: Holotype length 40 Ám, width 37 Ám, width of paracingulum about 5 Ám, width of parasutural septa about 4 Ám. Range, length 32-40 Ám, width 32-37 Ám.
Emended description: Fechner, 1985, p.120-121
The small cyst shows a more or less ellipsoidal outline. The epicyst is distinctly smaller than the hypocyst. An apical archeopyle is commonly developed. The denticulate crests marking the paratabulation, are distinctly higher on the hypocyst than on the epicyst. The parasulcus widens toward the antapex and borders upon the single antapical paraplate. The surface of the paraplates is slightly granular or scattered with tiny tubercles. Despite the absence of the operculum, including an unknown number of apical and intercalary paraplates, the following paratabulation formula is developed: (?"), (?a), 6", 6c, 6""", 1p, 1"""", 4s. The pictured cyst has a breadth of 25 Ám and a length of 30 Ám (without operculum).
Affinities:
Vozzhennikova 1967, p. 94-95: Microdinium dentatum differs from related forms in having a toothed crest on the boundaries of the plates and on the margin of the transverse furrow. Note: Some members of this species have a different shape of theca: in some it is ovoid, in others spherical. This is the basis for the separation of two forms: f. dentatum and f. sphaericum.
Fechner, 1985, p. 121: M. dentatum differs from M. setosum and M. irregulare in having denticulate parasutural crests, rather than rows of spines or undifferentiated septae. Because of the insufficient description and the obscure figures by Vozzhennikova 1967, both subspecies dentatum and sphaericum must be considered superfluous.