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Skuadinium biturbinatum
Skuadinium *biturbinatum Riding and Helby, 2001a, p.15, figs.8A–P. Holotype: Riding and Helby, 2001a, fig.8M. Age: early Toarcian.
Description. A species of Skuadinium which is longitudinally elongate and largely symmetrical about the paracingulum and parasulcus. Apical and antapical horns relatively short and broad with blunt or rounded distal terminations. Autophragm thin; smooth, microscabrate or microgranulate. The markedly laevorotatory paracinguum is indicated by low, smooth ridges. The parasulcus is indented. Discontinuous lineations of low-relief ornamentation sometimes present generally on the apical and antapical horns. Archaeopyle type unknown, possibly epicystal.
Dimensions (µm, n=28): Min. (Mean) Max.
Length: 55 (74) 86
Width: 39 (54) 63
The measured specimens are from sidewall core samples in Jabiru-10 (1790.00m), Skua-5 (2646.00m), Skua-6 (2385.00m) and Skua-7A (2440.00m) wells.
Comments. The outline is variable because the thin autophragm readily folds and tears. Additionally, the cyst is not always dorsoventrally flattened and may present in different directions. The paracingulum and parasulcus are usually the only indications of paratabulation, but short lineations, which may be paratabular, often occur close to the distal parts of the horns. A definite archaeopyle has not been observed; however, vague indications of an epicystal excystment aperture are present.
Comparison. Skuadinium biturbinatum differs from S. asymmetricum in being biconical and lacking reticulate surface features, and from S. reticulatum in lacking a reticulate autophragm.
Derivation of name. From the Latin prefix bi-, meaning two or double, and turbinatus, meaning conical or top-shaped.
Holotype and type locality. Fig. 8M, CPC 35177, Skua-6 well, sidewall core sample at 2385.00m.
Stratigraphical distribution. See Appendix 1 and Fig. 12.
Description. A species of Skuadinium which is longitudinally elongate and largely symmetrical about the paracingulum and parasulcus. Apical and antapical horns relatively short and broad with blunt or rounded distal terminations. Autophragm thin; smooth, microscabrate or microgranulate. The markedly laevorotatory paracinguum is indicated by low, smooth ridges. The parasulcus is indented. Discontinuous lineations of low-relief ornamentation sometimes present generally on the apical and antapical horns. Archaeopyle type unknown, possibly epicystal.
Dimensions (µm, n=28): Min. (Mean) Max.
Length: 55 (74) 86
Width: 39 (54) 63
The measured specimens are from sidewall core samples in Jabiru-10 (1790.00m), Skua-5 (2646.00m), Skua-6 (2385.00m) and Skua-7A (2440.00m) wells.
Comments. The outline is variable because the thin autophragm readily folds and tears. Additionally, the cyst is not always dorsoventrally flattened and may present in different directions. The paracingulum and parasulcus are usually the only indications of paratabulation, but short lineations, which may be paratabular, often occur close to the distal parts of the horns. A definite archaeopyle has not been observed; however, vague indications of an epicystal excystment aperture are present.
Comparison. Skuadinium biturbinatum differs from S. asymmetricum in being biconical and lacking reticulate surface features, and from S. reticulatum in lacking a reticulate autophragm.
Derivation of name. From the Latin prefix bi-, meaning two or double, and turbinatus, meaning conical or top-shaped.
Holotype and type locality. Fig. 8M, CPC 35177, Skua-6 well, sidewall core sample at 2385.00m.
Stratigraphical distribution. See Appendix 1 and Fig. 12.