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Helbydinium scabratum
From Fensome et al., 2019:
Helbydinium scabratum Snape, 1992, p.273,275, figs.6a–b,e. Holotype: Snape, 1992, figs.6a,e. Age: Tithonian. Age: Middleid Tithonian
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Diagnosis: Snape, 1992, p. 273
Cyst proximate, acavate with an elongate ellipsoidal outline. Apical archaeopyle, type (tA), operculum free. The archaeopyle and archaeopyle sutures are the only indications of paratabulation. Six precingular paraplates are present with the parasulcal notch in the mid-ventral position indicating a presumed gonyaulacacean paratabulation. The wall has two layers, the periphragm forming a sagittal flange or crest 3-5 µm in height. The endophragm is scabrate.
Description: Snape, 1992, p. 273
The species is proximate, usually dorso-ventrally compressed and elongate ellipsoidal in outline with rounded apical and antapical margins. The wall is acavate and is composed of two layers, the periphragm forming a nonparatabulate lamellar flange or crest. The flange is sagittal in position and up to 5 Ám in width. It may appear discontinuous in some specimens due to mechanical damage. The endophragm is scabrate. The archaeopyle is apical, type (tA), and is the only indication of paratabulation. Accessory archaeopyle sutures are developed. There are six precingular paraplates and the parasulcal notch is in the mid-ventral position indicating a gonyaulacacean arrangement.
Dimensions (µm) Min;Mean;Max
Overall length45; 51; 60
Overall width25; 29; 33
Crest width 3;3;5
Specimens measured: 8
Remarks: Snape, 1992, p. 275
Helby et al. (1988, fig.21, L, M) illustrated a cyst from the Puti Siltstone, Kawhia, New Zealand, designated as "gen. et sp. nov. C". This cyst appears to be similar to H. scabratum.
Fistulacysta simplex differs from H. scabratum in having tabulate crests and is larger in size.
Helbydinium scabratum Snape, 1992, p.273,275, figs.6a–b,e. Holotype: Snape, 1992, figs.6a,e. Age: Tithonian. Age: Middleid Tithonian
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Diagnosis: Snape, 1992, p. 273
Cyst proximate, acavate with an elongate ellipsoidal outline. Apical archaeopyle, type (tA), operculum free. The archaeopyle and archaeopyle sutures are the only indications of paratabulation. Six precingular paraplates are present with the parasulcal notch in the mid-ventral position indicating a presumed gonyaulacacean paratabulation. The wall has two layers, the periphragm forming a sagittal flange or crest 3-5 µm in height. The endophragm is scabrate.
Description: Snape, 1992, p. 273
The species is proximate, usually dorso-ventrally compressed and elongate ellipsoidal in outline with rounded apical and antapical margins. The wall is acavate and is composed of two layers, the periphragm forming a nonparatabulate lamellar flange or crest. The flange is sagittal in position and up to 5 Ám in width. It may appear discontinuous in some specimens due to mechanical damage. The endophragm is scabrate. The archaeopyle is apical, type (tA), and is the only indication of paratabulation. Accessory archaeopyle sutures are developed. There are six precingular paraplates and the parasulcal notch is in the mid-ventral position indicating a gonyaulacacean arrangement.
Dimensions (µm) Min;Mean;Max
Overall length45; 51; 60
Overall width25; 29; 33
Crest width 3;3;5
Specimens measured: 8
Remarks: Snape, 1992, p. 275
Helby et al. (1988, fig.21, L, M) illustrated a cyst from the Puti Siltstone, Kawhia, New Zealand, designated as "gen. et sp. nov. C". This cyst appears to be similar to H. scabratum.
Fistulacysta simplex differs from H. scabratum in having tabulate crests and is larger in size.