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Millioudodinium
From Williams et al., 2017:
[Millioudodinium, Stover and Evitt, 1978, p. 173; Emendation: Sarjeant, 1982b, p. 39
Type species: originally as Gonyaulacysta fetchamensis, Sarjeant, 1966b (pl.15, figs.1–2; text-fig.33)] ; Millioudodinium fetchamense, Stover and Evitt, 1978
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Original description: [Stover and Evitt, 1978]:
Synopsis:
Cysts proximate; autocyst subspherical to ellipsoidal, usually with a prominent apical horn; paratabulation gonyaulacacean, indicated by generally low parasutural ridges; paraplates without accessory ridges, septa, or other rectilinear markings; archeopyle precingular, Type P.
Description:
Shape: Subspherical to ellipsoidal, usually with a prominent apical horn.
Wall relationships: Generally autophragm only; wall usually of moderate thickness and frequently shows internal structuring; individual layers may be discernible on some species.
Wall features: Parasutural features, typically low ridges with smooth to granulate crests. Paraplates lack accessory ridges, septa, or other rectilinear markings, but may be variously ornamented with features of low relief.
Paratabulation: Indicated by parasutural features; gonyaulacacean, formula: 3-4`, O-la, 6``, X-6c, 5-6```, lp, 1````, 0-3s.
Archeopyle: Precingular, Type P (3`` only, may be enlarged); operculum free.
Paracingulum: Indicated generally by parallel, transverse, equatorial ridges, or, rarely, by six subrectangular paraplates.
Parasulcus: Generally delimited by parasutural features, confined mostly to hypocyst; may be subdivided .
Size: Intermediate to large.
Affinities:
Millioudodinium differs from Apteodinium in having parasutural ridges, which are lacking on Apteodinium or only faintly and inconsistently expressed. The new genus differs from Cribroperidinium in lacking accessory ridges or septa on the paraplates.
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Emended description:
Sarjeant, 1982:
Diagnosis:
Proximate to proximochorate dinoflagellate cysts, typically of intermediate to large, rarely of small, size.
Ambitus spheroidal to broadly ellipsoidal or subpolygonal, typically with an apical prominence or horn: acavate to cornucavate. Lines, low ridges or smooth to regularly or irregularly serrate crests of small height mark the parasutures; accessory crests are developed only to a very restricted degree or not at all.
Paratabulation 0-?2pa, 3-4`, 0-?2a, 6", 6-?7c, 5-6```, Ip, 1````, 0-3s. Paraplate 4` is elongate, almost as long as 1` and having only a short boundary with 6"; the latter paraplate is typically roughly triangular, with concave to markedly convex lateral flanks. The boundary between paraplates 4` and 6" intersects the right lateral boundary of 1` in a position anterior to the junction of the latter paraplate with the sulcus. Gonal spinules are lacking. Surface of phragma smooth, granular, nodose, punctate or reticulate.
Archaeopyle single-plate precingular, formed by loss of paraplate 3`.
[Millioudodinium, Stover and Evitt, 1978, p. 173; Emendation: Sarjeant, 1982b, p. 39
Type species: originally as Gonyaulacysta fetchamensis, Sarjeant, 1966b (pl.15, figs.1–2; text-fig.33)] ; Millioudodinium fetchamense, Stover and Evitt, 1978
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Stover and Evitt, 1978]:
Synopsis:
Cysts proximate; autocyst subspherical to ellipsoidal, usually with a prominent apical horn; paratabulation gonyaulacacean, indicated by generally low parasutural ridges; paraplates without accessory ridges, septa, or other rectilinear markings; archeopyle precingular, Type P.
Description:
Shape: Subspherical to ellipsoidal, usually with a prominent apical horn.
Wall relationships: Generally autophragm only; wall usually of moderate thickness and frequently shows internal structuring; individual layers may be discernible on some species.
Wall features: Parasutural features, typically low ridges with smooth to granulate crests. Paraplates lack accessory ridges, septa, or other rectilinear markings, but may be variously ornamented with features of low relief.
Paratabulation: Indicated by parasutural features; gonyaulacacean, formula: 3-4`, O-la, 6``, X-6c, 5-6```, lp, 1````, 0-3s.
Archeopyle: Precingular, Type P (3`` only, may be enlarged); operculum free.
Paracingulum: Indicated generally by parallel, transverse, equatorial ridges, or, rarely, by six subrectangular paraplates.
Parasulcus: Generally delimited by parasutural features, confined mostly to hypocyst; may be subdivided .
Size: Intermediate to large.
Affinities:
Millioudodinium differs from Apteodinium in having parasutural ridges, which are lacking on Apteodinium or only faintly and inconsistently expressed. The new genus differs from Cribroperidinium in lacking accessory ridges or septa on the paraplates.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Sarjeant, 1982:
Diagnosis:
Proximate to proximochorate dinoflagellate cysts, typically of intermediate to large, rarely of small, size.
Ambitus spheroidal to broadly ellipsoidal or subpolygonal, typically with an apical prominence or horn: acavate to cornucavate. Lines, low ridges or smooth to regularly or irregularly serrate crests of small height mark the parasutures; accessory crests are developed only to a very restricted degree or not at all.
Paratabulation 0-?2pa, 3-4`, 0-?2a, 6", 6-?7c, 5-6```, Ip, 1````, 0-3s. Paraplate 4` is elongate, almost as long as 1` and having only a short boundary with 6"; the latter paraplate is typically roughly triangular, with concave to markedly convex lateral flanks. The boundary between paraplates 4` and 6" intersects the right lateral boundary of 1` in a position anterior to the junction of the latter paraplate with the sulcus. Gonal spinules are lacking. Surface of phragma smooth, granular, nodose, punctate or reticulate.
Archaeopyle single-plate precingular, formed by loss of paraplate 3`.