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Pentadinium taeniagerum ssp. imaginatum
From Fensome et al., 2019:
Pentadinium taeniagerum ssp. imaginatum Benedek, 1972, p.45–46, pl.6, figs.12a–b. Emendation: Benedek et al., 1982, p.279,281, as Toenisbergia imaginata. Holotype: Benedek, 1972, pl.6, figs.12a–b; Eisenack and Kjellström, 1975a, first page labelled "nach S.646"; Benedek et al., 1982, figs.7A,C,E,8C–D (not 8A–B); Fensome et al., 1995, figs.1–4 — p.1557. Originally (and now) Pentadinium taeniagerum subsp. imaginatum, subsequently Toenisbergia imaginatum. Lentin and Williams (1985, p.279) retained this taxon as Pentadinium laticinctum subsp. imaginatum. Taxonomic junior synonym: Pentadinium laticinctum subsp. imaginatum, according to Benedek et al. (1982, p.279) — however, Lentin and Williams (1985, p.279) retained Pentadinium laticinctum subsp. imaginatum. Age: Late Oligocene.
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Original description: [Benedek, 1972] (translated from German):
Pentadinium laticinchum imaginatum n. subsp.
Derivatio nominis: imago = present, but not visible.
Holotype: The specimen preserved in specimen 421/109/3 and illustrated in Plate 6, Fig. 9.
Locus typicus: Tönisberg, Lower Rhine.
Stratum typicalum: Upper Oligocene.
Diagnosis: A subspecies of P. laticinctum Gerlach, whose capsule shell lacks any venation.
Description: The dark yellow, thick-walled inner capsule is spherical and enclosed by a thin-walled, crystal-clear, unvenationed outer shell. The position of the transverse furrow is indicated by slight constrictions at the site of the sutures. The inner capsule is firmly fused to the outer shell in the apical and anta-pical regions. A pyloma appears at the site of the third precingulate plate.
Remarks: This form resembles P. laticinctum (GERLACH 1961) in size and outline, but can be clearly distinguished from it and other subspecies in the Tönisberg material by the absence of a pelmet. Most specimens are characterized by open pylomas. However, Plate 2, Fig. 11ab, records the only exceptional case where the lid is still present in situ.
The dimensions of this specimen (capsule O 52u/62u) remain below those of the open P. laticinctum. The rarity or absence of the closed stage in the Eocene and Oligocene samples examined so far, which often contain a considerable number of pentadinia, is explained by the fact that the "mature stage" was usually reached. Some factors may have interrupted the developmental cycle and, in the present case, preserved an immature cyst.
Dimensions: capsule Ø 65μ (63μ/70μ), specimen Ø 97μ (95μ/100μ), holotype Ø 65μ, specimen 98μ/100μ (10 measurements). Number of specimens examined: 10.
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Emended diagnosis: Benedek et al., 1982, p. 21-22
Cyst circumcavate. Periblast rounded-hexagonal in polar view (with a marked sulcal indentation), irregularly subpolygonal in ambitus, with outbulges at the apex and equator and with antapex rather flat. Endoblast ovoidal to rounded-subpolygonal, thick and two-layered (mesophragm + endophragm). Horns absent; crests and processes lacking. Cingulum not clearly defined, but faintly suggested by equatorial folding: sulcus not readily visible in lateral view, but clearly indicated in polar view by the ventral inbulge of the periblast. Archaeopyle intercalary (type I/I); very large in the periblast, with archaeopyle index greater than 0.5, somewhat smaller proportionately in the endoblast. Surface of periphragm lightly granular; endoblast apparently punctate, surface of mesophragm granular.
Pentadinium taeniagerum ssp. imaginatum Benedek, 1972, p.45–46, pl.6, figs.12a–b. Emendation: Benedek et al., 1982, p.279,281, as Toenisbergia imaginata. Holotype: Benedek, 1972, pl.6, figs.12a–b; Eisenack and Kjellström, 1975a, first page labelled "nach S.646"; Benedek et al., 1982, figs.7A,C,E,8C–D (not 8A–B); Fensome et al., 1995, figs.1–4 — p.1557. Originally (and now) Pentadinium taeniagerum subsp. imaginatum, subsequently Toenisbergia imaginatum. Lentin and Williams (1985, p.279) retained this taxon as Pentadinium laticinctum subsp. imaginatum. Taxonomic junior synonym: Pentadinium laticinctum subsp. imaginatum, according to Benedek et al. (1982, p.279) — however, Lentin and Williams (1985, p.279) retained Pentadinium laticinctum subsp. imaginatum. Age: Late Oligocene.
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Original description: [Benedek, 1972] (translated from German):
Pentadinium laticinchum imaginatum n. subsp.
Derivatio nominis: imago = present, but not visible.
Holotype: The specimen preserved in specimen 421/109/3 and illustrated in Plate 6, Fig. 9.
Locus typicus: Tönisberg, Lower Rhine.
Stratum typicalum: Upper Oligocene.
Diagnosis: A subspecies of P. laticinctum Gerlach, whose capsule shell lacks any venation.
Description: The dark yellow, thick-walled inner capsule is spherical and enclosed by a thin-walled, crystal-clear, unvenationed outer shell. The position of the transverse furrow is indicated by slight constrictions at the site of the sutures. The inner capsule is firmly fused to the outer shell in the apical and anta-pical regions. A pyloma appears at the site of the third precingulate plate.
Remarks: This form resembles P. laticinctum (GERLACH 1961) in size and outline, but can be clearly distinguished from it and other subspecies in the Tönisberg material by the absence of a pelmet. Most specimens are characterized by open pylomas. However, Plate 2, Fig. 11ab, records the only exceptional case where the lid is still present in situ.
The dimensions of this specimen (capsule O 52u/62u) remain below those of the open P. laticinctum. The rarity or absence of the closed stage in the Eocene and Oligocene samples examined so far, which often contain a considerable number of pentadinia, is explained by the fact that the "mature stage" was usually reached. Some factors may have interrupted the developmental cycle and, in the present case, preserved an immature cyst.
Dimensions: capsule Ø 65μ (63μ/70μ), specimen Ø 97μ (95μ/100μ), holotype Ø 65μ, specimen 98μ/100μ (10 measurements). Number of specimens examined: 10.
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Emended diagnosis: Benedek et al., 1982, p. 21-22
Cyst circumcavate. Periblast rounded-hexagonal in polar view (with a marked sulcal indentation), irregularly subpolygonal in ambitus, with outbulges at the apex and equator and with antapex rather flat. Endoblast ovoidal to rounded-subpolygonal, thick and two-layered (mesophragm + endophragm). Horns absent; crests and processes lacking. Cingulum not clearly defined, but faintly suggested by equatorial folding: sulcus not readily visible in lateral view, but clearly indicated in polar view by the ventral inbulge of the periblast. Archaeopyle intercalary (type I/I); very large in the periblast, with archaeopyle index greater than 0.5, somewhat smaller proportionately in the endoblast. Surface of periphragm lightly granular; endoblast apparently punctate, surface of mesophragm granular.