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Microdinium bensonii ssp. pilatum
From Fensome et al., 2019:
Microdinium bensonii subsp. pilatum Slimani, 1994, p.27, pl.4, figs.6–9,18–21. Holotype: Slimani, 1994, pl.4, figs.7–9,18–19. Age: late Campanian–earliest Danian.
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Original description (Slimani, 1994):
Microdinium bensonii subsp. pilatum sp. nov. (PI.4, Fig.6-9,18-21)
Name derivation: Latin: pila, pillar, intratabular pillars that support the periphragm.
Holotvpe: Turnhout -933 m, preparation 5, E.F. coord. N26/2.
Paratvpe: Turnhout -933 m, preparation 2, E.F. coord. C37/4.
Type locality: Turnhout -933 m.
Type horizon: Upper Campanian.
Diagnosis: This is a subspecies of Microdinium bensonii, characterized by the presence of a few pillars that support the periphragm in the central region of the intratabular areas.
Dimensions: Holotype: maximum diameter: 24 µm.
Variations: Maximum diameter: 24-28 µm.
Number of specimens measured: 8.
Material: 15 specimens.
Description: Small subspheroidal to ovoid cyst, with a hypocyst twice as short as the epicyst. The endophragm is thick (about 1 pm) and smooth, while the periphragm is very thin, hyaline and also smooth. The latter is supported by penitabular ridges and intratabular pillars (1 to 1.5 µm high). The parasutural areas between the penitabular ridges are narrow (1 to 2 µm wide) and devoid of ornamentation, with a periphragm probably interrupted or concave. The paratabulation is of the partiform gonyaulacoid type: 1 pr, 4', 4a, 6", 6c, 6"', lp, 1"", l-5s. The paraplate 1"" is hexagonal; lp is smaller and pentagonal; 1" is distinctly small and subtriangular. The paracingulum is not spiral; the parasulcus is apparently segmented into 5 small paraplates. The archaeopyle (6 to 8 µm wide) is apical and intercalary, of type (tAtl)a. The operculum is attached ventrally, it is composed of 4 apical paraplates, 4 anterior intercalary ones and 1 preapical one.
Note: Microdinium bensonii subsp. pilatum sp. nov. is characterized by the presence of intratabular pillars that support the periphragm; therefore, it is distinguished from M. bensonii subsp. bensonii sp. nov., which lacks them.
Stratigraphic distribution: Turnhout: -933 to -759.89 m, Upper Campanian - Late Maastrichtian, Early Danian.
Microdinium bensonii subsp. pilatum Slimani, 1994, p.27, pl.4, figs.6–9,18–21. Holotype: Slimani, 1994, pl.4, figs.7–9,18–19. Age: late Campanian–earliest Danian.
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Original description (Slimani, 1994):
Microdinium bensonii subsp. pilatum sp. nov. (PI.4, Fig.6-9,18-21)
Name derivation: Latin: pila, pillar, intratabular pillars that support the periphragm.
Holotvpe: Turnhout -933 m, preparation 5, E.F. coord. N26/2.
Paratvpe: Turnhout -933 m, preparation 2, E.F. coord. C37/4.
Type locality: Turnhout -933 m.
Type horizon: Upper Campanian.
Diagnosis: This is a subspecies of Microdinium bensonii, characterized by the presence of a few pillars that support the periphragm in the central region of the intratabular areas.
Dimensions: Holotype: maximum diameter: 24 µm.
Variations: Maximum diameter: 24-28 µm.
Number of specimens measured: 8.
Material: 15 specimens.
Description: Small subspheroidal to ovoid cyst, with a hypocyst twice as short as the epicyst. The endophragm is thick (about 1 pm) and smooth, while the periphragm is very thin, hyaline and also smooth. The latter is supported by penitabular ridges and intratabular pillars (1 to 1.5 µm high). The parasutural areas between the penitabular ridges are narrow (1 to 2 µm wide) and devoid of ornamentation, with a periphragm probably interrupted or concave. The paratabulation is of the partiform gonyaulacoid type: 1 pr, 4', 4a, 6", 6c, 6"', lp, 1"", l-5s. The paraplate 1"" is hexagonal; lp is smaller and pentagonal; 1" is distinctly small and subtriangular. The paracingulum is not spiral; the parasulcus is apparently segmented into 5 small paraplates. The archaeopyle (6 to 8 µm wide) is apical and intercalary, of type (tAtl)a. The operculum is attached ventrally, it is composed of 4 apical paraplates, 4 anterior intercalary ones and 1 preapical one.
Note: Microdinium bensonii subsp. pilatum sp. nov. is characterized by the presence of intratabular pillars that support the periphragm; therefore, it is distinguished from M. bensonii subsp. bensonii sp. nov., which lacks them.
Stratigraphic distribution: Turnhout: -933 to -759.89 m, Upper Campanian - Late Maastrichtian, Early Danian.