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Pentadinium corium
Pentadinium corium Schiøler, 2005, p.29–30, pl.8, figs.11–12,16–18; text-fig.6.
Holotype: Schiøler, 2005, pl.8, figs.17–18 (Horizon: Lark Formation, 5630–5660# (1716.0–1725.2 m); Middle Chattian.)
Age: Rupelian–Chattian
Stratigraphical range: Rupelian to Chattian in the Alma-1X well.
Original description (Schioler, 2005): Pentadinium corium sp. nov. (Pl. 8, figs 11–12, 16–18; Fig. 6)
Diagnosis:
Suturocavate, gonyaulacoid cyst with a thick, spongy endophragm and a thin periphragm that forms very low, ondulating, parasutural ridges on the endophragm. Archaeopyle precingular, type P3´´.
Description:
Small to intermediate-sized suturocavate, gonyaulacoid cyst. The cyst is circular to sub-circular in outline and is composed of two wall layers.
Wall: The endophragm is thick (4–5 µm), ‘spongy’ and lanate in cross-section, finely pitted and granulate in surface view. The periphragm is thin and smooth (periphragm thickness: <0.25 µm). The endophragm and periphragm are closely appressed except where the periphragm rises to form low, slightly ondulating, cavate ridges on the endophragm (ridge height: 1–3 µm). The ridges are generally parasutural, but small, accessory, cavate folds often extend from the parasutural ridges some distance onto the paraplates (Fig. 6). Small, discrete, cavate folds may also raise in intratabular position (Fig. 6).
Archaeopyle: precingular, type P3´´
Paratabulation: only incompletely indicated by parasutural folds on the periphragm. It is often masked by accessory folds in the periphragm and by the dark-coloured thick endophragm. When visible, the paratabulation is gonyaulacoid, S-type sexiform with the plate formula: ?’, 6’’, ?c, 6’’’, 1p, 1’’’’, ?s. (Taylor-Evitt notation of the hypocyst is shown in Fig. 6.)
Dimensions in µm; 15 specimens measured
Holotype: length 53; width 46; sutural ridge height 2
Range: length 44 (50) 56; width 45 (48) 52; sutural ridge height 2-3
Affinities/Remarks:
Pentadinium corium is distinguished from most other species of the genus Pentadinium by its smaller size, its low parasutural ridges and the ‘spongy’ and lanate structure of the endocyst wall. Pentadinium favatum Edwards, 1982, P. goniferum Edwards, 1982 and P. membranaceum (Eisenack, 1965) Stover & Evitt, 1978 all have a relatively thick, finely ornamented endocyst wall, but differ in being bigger and in having much higher parasutural ridges (crests). Pentadinium favatum differs further in having a meshlike, perforate periphragm. The new species resembles species of the genera Impagidinium and Leptodinium that possess a thick cyst wall (e.g. Impagidinium pentahedrias Damassa, 1979; Leptodinium clathratum (Cookson & Eisenack, 1960) Sarjeant in Davey et al., 1969), but it differs in possessing a periphragm that forms cavate parasutural and intraplate ridges.
Holotype: Schiøler, 2005, pl.8, figs.17–18 (Horizon: Lark Formation, 5630–5660# (1716.0–1725.2 m); Middle Chattian.)
Age: Rupelian–Chattian
Stratigraphical range: Rupelian to Chattian in the Alma-1X well.
Original description (Schioler, 2005): Pentadinium corium sp. nov. (Pl. 8, figs 11–12, 16–18; Fig. 6)
Diagnosis:
Suturocavate, gonyaulacoid cyst with a thick, spongy endophragm and a thin periphragm that forms very low, ondulating, parasutural ridges on the endophragm. Archaeopyle precingular, type P3´´.
Description:
Small to intermediate-sized suturocavate, gonyaulacoid cyst. The cyst is circular to sub-circular in outline and is composed of two wall layers.
Wall: The endophragm is thick (4–5 µm), ‘spongy’ and lanate in cross-section, finely pitted and granulate in surface view. The periphragm is thin and smooth (periphragm thickness: <0.25 µm). The endophragm and periphragm are closely appressed except where the periphragm rises to form low, slightly ondulating, cavate ridges on the endophragm (ridge height: 1–3 µm). The ridges are generally parasutural, but small, accessory, cavate folds often extend from the parasutural ridges some distance onto the paraplates (Fig. 6). Small, discrete, cavate folds may also raise in intratabular position (Fig. 6).
Archaeopyle: precingular, type P3´´
Paratabulation: only incompletely indicated by parasutural folds on the periphragm. It is often masked by accessory folds in the periphragm and by the dark-coloured thick endophragm. When visible, the paratabulation is gonyaulacoid, S-type sexiform with the plate formula: ?’, 6’’, ?c, 6’’’, 1p, 1’’’’, ?s. (Taylor-Evitt notation of the hypocyst is shown in Fig. 6.)
Dimensions in µm; 15 specimens measured
Holotype: length 53; width 46; sutural ridge height 2
Range: length 44 (50) 56; width 45 (48) 52; sutural ridge height 2-3
Affinities/Remarks:
Pentadinium corium is distinguished from most other species of the genus Pentadinium by its smaller size, its low parasutural ridges and the ‘spongy’ and lanate structure of the endocyst wall. Pentadinium favatum Edwards, 1982, P. goniferum Edwards, 1982 and P. membranaceum (Eisenack, 1965) Stover & Evitt, 1978 all have a relatively thick, finely ornamented endocyst wall, but differ in being bigger and in having much higher parasutural ridges (crests). Pentadinium favatum differs further in having a meshlike, perforate periphragm. The new species resembles species of the genera Impagidinium and Leptodinium that possess a thick cyst wall (e.g. Impagidinium pentahedrias Damassa, 1979; Leptodinium clathratum (Cookson & Eisenack, 1960) Sarjeant in Davey et al., 1969), but it differs in possessing a periphragm that forms cavate parasutural and intraplate ridges.