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Dissiliodinium fragile
From Fensome et al., 2019:
Dissiliodinium fragile (Kunz, 1990, p.22–23, pl.4, figs.11a–b,12a–b,13,14a–b,15; text-figs.9a–c) Feist-Burkhardt and Monteil, 2001, p.62. Holotype: Kunz, 1990, pl.4, figs.11a–b; figs.11a–b; text-figs.9a–c. Originally Okerisphaeridium, subsequently (and now) Dissiliodinium. Age: late Oxfordian.
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Original description: [Kunz, 1990] (translated from German):
Okerisphaeridium fragile n. gen. n. sp.
Plate 4, Figs. 1a-b., 12a-b., 13, 14a-b, 15, Figs. 9a-c
Derivio nominis: Latin fragile = fragile, in reference to the easily crushable cysts of this species.
Holotype: Specimen 32/A21-32. Plate 4, Figs. 1a-b, 9a-c.
Paratype: Specimen 32/A21-33. Plate 4, Figs. 12a-b.
Typical location: Oker Kalkwerke quarry, TK 4029 Vienenburg. Coordinates: R 4397402, H 5753132.
Typical stratum: Upper coral oolite, layer A21 (see profile of the Oker limestone works). - Oolitic calcareous marlstone.
Description: The proximal cyst of spheroidal to subspheroidal circumference has an areation formula ?pr, 4, 0a, 6'', 6c, 6'", 1p, 1''", xs. The archaeopyle is formed by the detachment of four precingulate areas, with the archaeopyle formula being 2"+3"+4"+5". The operculum is segregated and fragments into individual plates (= solvate). The opercular formula is 2s"+3s"+4s"+5s". The epicyst and hypocyst of approximately equal size are separated by a spiral cingulate (cingulate offset approximately 1.5 cingulate widths). The antapical plate is typically sexiform. The wall consists of a pedium and luxuria. The surface ornamentation of individual individuals differs; some possess only granules, while in others these fuse to form irregularly arranged and short ridges. The finis are characterized by a reduction in surface ornamentation. Luxuriate elements such as ribs, septa, or processes are absent in this species. Horns are also not developed.
Dimensions: Holotype 48 μm diameter.
Other measured specimens: 20–42–54 μm diameter, average 47 μm.
Occurrence: The species was found in two samples of the Middle and Upper Coral Oolite (Oker Limestone Works). It occurs sporadically to widely in these samples.
Remarks: The closest related species is Dissiliodinium globulum DRUGG 1978. However, this species lacks hypocystal areation and its archaeopyle is formed by the loss of six precingulate areas. Isolated individuals with an archaeopyle apparently developed from only two or three missing areas (Plate 4, Fig. 14a) are interpreted as unhatched cysts, in which the two or three most easily removed areas were lost during preparation. This is also supported by the fact that many individuals of this species certainly did not undergo excystization and here all the areas considered for archaeopyle formation Areae are still present in situ.
Dissiliodinium fragile (Kunz, 1990, p.22–23, pl.4, figs.11a–b,12a–b,13,14a–b,15; text-figs.9a–c) Feist-Burkhardt and Monteil, 2001, p.62. Holotype: Kunz, 1990, pl.4, figs.11a–b; figs.11a–b; text-figs.9a–c. Originally Okerisphaeridium, subsequently (and now) Dissiliodinium. Age: late Oxfordian.
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Original description: [Kunz, 1990] (translated from German):
Okerisphaeridium fragile n. gen. n. sp.
Plate 4, Figs. 1a-b., 12a-b., 13, 14a-b, 15, Figs. 9a-c
Derivio nominis: Latin fragile = fragile, in reference to the easily crushable cysts of this species.
Holotype: Specimen 32/A21-32. Plate 4, Figs. 1a-b, 9a-c.
Paratype: Specimen 32/A21-33. Plate 4, Figs. 12a-b.
Typical location: Oker Kalkwerke quarry, TK 4029 Vienenburg. Coordinates: R 4397402, H 5753132.
Typical stratum: Upper coral oolite, layer A21 (see profile of the Oker limestone works). - Oolitic calcareous marlstone.
Description: The proximal cyst of spheroidal to subspheroidal circumference has an areation formula ?pr, 4, 0a, 6'', 6c, 6'", 1p, 1''", xs. The archaeopyle is formed by the detachment of four precingulate areas, with the archaeopyle formula being 2"+3"+4"+5". The operculum is segregated and fragments into individual plates (= solvate). The opercular formula is 2s"+3s"+4s"+5s". The epicyst and hypocyst of approximately equal size are separated by a spiral cingulate (cingulate offset approximately 1.5 cingulate widths). The antapical plate is typically sexiform. The wall consists of a pedium and luxuria. The surface ornamentation of individual individuals differs; some possess only granules, while in others these fuse to form irregularly arranged and short ridges. The finis are characterized by a reduction in surface ornamentation. Luxuriate elements such as ribs, septa, or processes are absent in this species. Horns are also not developed.
Dimensions: Holotype 48 μm diameter.
Other measured specimens: 20–42–54 μm diameter, average 47 μm.
Occurrence: The species was found in two samples of the Middle and Upper Coral Oolite (Oker Limestone Works). It occurs sporadically to widely in these samples.
Remarks: The closest related species is Dissiliodinium globulum DRUGG 1978. However, this species lacks hypocystal areation and its archaeopyle is formed by the loss of six precingulate areas. Isolated individuals with an archaeopyle apparently developed from only two or three missing areas (Plate 4, Fig. 14a) are interpreted as unhatched cysts, in which the two or three most easily removed areas were lost during preparation. This is also supported by the fact that many individuals of this species certainly did not undergo excystization and here all the areas considered for archaeopyle formation Areae are still present in situ.