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Oligosphaeridium balticum
Oligokolpoma balticus Iakovleva et al., (2021), Plate 1, figures 1–3, 5–7, 9–10, 13–14; Plate 2, figures 1–3, 6–8, 10–12; Plate 3, figures 1–3, 5–7, 10–11, 14–15; Plate 6, figures 3–4, 7, 11–13; Figure 10.
Synonymy. Oligosphaeridium? sp. cf. Hystrichokolpoma rigaudiae Deflandre and Cookson 1955 in De Coninck (1986), pl. 6, figs. 15, 16.
Holotype. Plate 1, figures 1–3, 5–7; slide P-1-Ob, England Finder coordinates J43/1.
Type stratum and locality. Sample 15 ( 11.0m bsl), ‘White Wall’ Member, Prussian Formation, Primorsky Quarry outcrop
section, Sambia Peninsula, Russian Federation.
Diagnosis. Cribroperidinioid acavate chorate cyst of intermediate size, with ellipsoidal smooth or finely granulate central body and 14 narrow processes; processes expand distally into clypeate features, except arrow-shaped antapical one; archaeopyle apical, operculum free.
Description. Cyst chorate with ellipsoidal central body; autophragm only. Central body smooth or finely granulate, bears 14 intratabular processes. Processes are simple, tubular, and relatively narrow; their stems (except the antapical one) expand distally into more or less developed clypeate features. Antapical process is arrow-shaped, closed at its extremity, ornamented by few small tubercles. Processes may vary slightly in length and width, their size possibly depend on the size of corresponding paraplate. When the specimen is well preserved, the bases of processes are marked by lines forming quadrangular areas indicating plates. Archeopyle is apical, with angular margin, operculum free. Presumably, this species might possess four apical processes. Tabulation is gonyaulacacean, indicated by intratabular processes
and archaeopyle; one process per plate processes formula is 40, 60’, 1 as, 0c, 60’’, 10’’’ (Figure 10). Cingulum typically expressed by the absence of processes. Sulcus is not observed.
Dimensions. Holotype: length of central body 36 mm; width of central body 32 mm; mean length of processes 24 mm; length of antapical process 28 mm. Dimensions of measured specimens: length of central body 33–43 mm (mean value 38 mm); width of central body 30–38 mm (mean value 35.5 mm); length of processes 10–28 mm (mean value 23 mm); length of antapical process 28–37 mm (mean value 31.5 mm).
Eight specimens measured.
Comparison. Oligokolpoma balticus sp. nov. is similar to Hystrichokolpoma rigaudiae Deflandre and Cookson 1955 (especially in feature of antapical process), but differs by the absence of cingular and, probably, sulcal processes. Oligokolpoma balticus sp. nov. differs from the type-species Oligokolpoma tubulus Fensome et al. 2009 and Oligokolpoma galeottii Pross et al. 2010 by significantly longer and narrower
processes, by the characteristic clypeate features on their distal terminations and by the shape of antapical process.
Stratigraphical range. Bartonian–Priabonian.
Derivation of name. From Baltic coast, where the holotype was found.
Comments. In the type locality Oligokolpoma balticus sp. nov. occurs throughout the whole Prussian and Palv e formations, always in small quantities, no more than 0.5–1.5% of assemblage.
Synonymy. Oligosphaeridium? sp. cf. Hystrichokolpoma rigaudiae Deflandre and Cookson 1955 in De Coninck (1986), pl. 6, figs. 15, 16.
Holotype. Plate 1, figures 1–3, 5–7; slide P-1-Ob, England Finder coordinates J43/1.
Type stratum and locality. Sample 15 ( 11.0m bsl), ‘White Wall’ Member, Prussian Formation, Primorsky Quarry outcrop
section, Sambia Peninsula, Russian Federation.
Diagnosis. Cribroperidinioid acavate chorate cyst of intermediate size, with ellipsoidal smooth or finely granulate central body and 14 narrow processes; processes expand distally into clypeate features, except arrow-shaped antapical one; archaeopyle apical, operculum free.
Description. Cyst chorate with ellipsoidal central body; autophragm only. Central body smooth or finely granulate, bears 14 intratabular processes. Processes are simple, tubular, and relatively narrow; their stems (except the antapical one) expand distally into more or less developed clypeate features. Antapical process is arrow-shaped, closed at its extremity, ornamented by few small tubercles. Processes may vary slightly in length and width, their size possibly depend on the size of corresponding paraplate. When the specimen is well preserved, the bases of processes are marked by lines forming quadrangular areas indicating plates. Archeopyle is apical, with angular margin, operculum free. Presumably, this species might possess four apical processes. Tabulation is gonyaulacacean, indicated by intratabular processes
and archaeopyle; one process per plate processes formula is 40, 60’, 1 as, 0c, 60’’, 10’’’ (Figure 10). Cingulum typically expressed by the absence of processes. Sulcus is not observed.
Dimensions. Holotype: length of central body 36 mm; width of central body 32 mm; mean length of processes 24 mm; length of antapical process 28 mm. Dimensions of measured specimens: length of central body 33–43 mm (mean value 38 mm); width of central body 30–38 mm (mean value 35.5 mm); length of processes 10–28 mm (mean value 23 mm); length of antapical process 28–37 mm (mean value 31.5 mm).
Eight specimens measured.
Comparison. Oligokolpoma balticus sp. nov. is similar to Hystrichokolpoma rigaudiae Deflandre and Cookson 1955 (especially in feature of antapical process), but differs by the absence of cingular and, probably, sulcal processes. Oligokolpoma balticus sp. nov. differs from the type-species Oligokolpoma tubulus Fensome et al. 2009 and Oligokolpoma galeottii Pross et al. 2010 by significantly longer and narrower
processes, by the characteristic clypeate features on their distal terminations and by the shape of antapical process.
Stratigraphical range. Bartonian–Priabonian.
Derivation of name. From Baltic coast, where the holotype was found.
Comments. In the type locality Oligokolpoma balticus sp. nov. occurs throughout the whole Prussian and Palv e formations, always in small quantities, no more than 0.5–1.5% of assemblage.