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Sokolovidinium sphaericum
Sokolovidinium sphaericum (Vozzhennikova, 1967, p.95–96, pl.36, figs.2a–b; pl.38, figs.1a–b) Lentin and Vozzhennikova, 1990, p.114–116. Emendation: Lentin and Vozzhennikova, 1990, p.115, as Sokolovidinium sphaericum
Originally Microdinium dentatum forma sphaericum, subsequently Microdinium dentatum ssp. sphaericum, thirdly (and now) Sokolovidinium sphaericum. At the time of the transfer, Lentin and Vozzhennikova, 1990 provided an emended description for this taxon and raised it to the species level.
Holotype: Vozzhennikova, 1967, pl.38, figs.1a–b; Lentin and Vozzhennikova, 1990, pl.13, figs.5–6; text-fig.67.
Locus typicus: Smolensk region, Russia
Stratum typicum: Senonian
Translation Vozzhennikova, 1967: Lentin and Vozzhennikova, 1990
Original descrpition: Vozzhennikova, 1967, p.95-96: Microdinium dentatum forma sphaericum
Theca ovoid, separated by the transverse furrow into a small epitheca and a large hypotheca. The transverse furrow is broad, the longitudinal furrow extends to the, antapex. Plates bounded by a light colored toothed crest. Thecal surface granular.
Emended description: Lentin and Vozzhennikova, 1990, p.115
Cyst shape subsphaerical to polyhedral; epicyst about 1/3 the length of hypocyst. Autophragm coarsely granulose; ectophragm very thin, porate, appressed to autophragm in intratabular areas; parasutures defined by suturocavate crests which are perforate, margins of the crests are undulose with very long solid, simple acuminate gonal processes, 10-40Ám in length. Paratabulation indicated by parasutural crests and position of gonal processes; formula: 4", 6-7"", 6-7c, 5-6""", 1P (?), 1"""". Archeopyle precingular, Type P (3""only). Paracingulum inticated by six (? seven) elongate rectangular paraplates which are outlined by parasutural crests; paracingulum divided cyst into two unequal parts, epicyst being about 1/3 the length of the hypocyst. Parasulcal area outlined by parasutural crests and may be subdivided by small paraplates. Size: Holotype, diameter 30 µm, width of paracingulum about 5 µm, height of parasutural ridges 3-5 µm. Length of gonal processes 20-35 µm. Range of cyst length 29-32 µm.
Affinities:
Lentin and Vozzhennikova, 1990, p.115: Sokolovidinium spbaericum most closely resembles species of the genus Microdinium. However the distinctive gonal processes and the precingular archeopyle distinguish it from that group. S. sphaericum is very small and the long processes nearly invisible in light microscopy. The orignal description of "toothed crests" on this taxon was a result of distortion of light through the porate sutural crests. The margins of the crests are smooth to slightly undulose. ?Microdinium horridum (Below) Lentin and Williams, 1989 has short gonal processes. However, it is dorsoventrally flattened, has an apical archaeopyle with complex apical paratabulation and two antapical paraplates which are not seen in Sokolovidinium. In addition, because Below only illustrates only exterior morphology of the species M. horridum it is impossible to interpret the nature of the wall structure or suturocavation, if any.
Originally Microdinium dentatum forma sphaericum, subsequently Microdinium dentatum ssp. sphaericum, thirdly (and now) Sokolovidinium sphaericum. At the time of the transfer, Lentin and Vozzhennikova, 1990 provided an emended description for this taxon and raised it to the species level.
Holotype: Vozzhennikova, 1967, pl.38, figs.1a–b; Lentin and Vozzhennikova, 1990, pl.13, figs.5–6; text-fig.67.
Locus typicus: Smolensk region, Russia
Stratum typicum: Senonian
Translation Vozzhennikova, 1967: Lentin and Vozzhennikova, 1990
Original descrpition: Vozzhennikova, 1967, p.95-96: Microdinium dentatum forma sphaericum
Theca ovoid, separated by the transverse furrow into a small epitheca and a large hypotheca. The transverse furrow is broad, the longitudinal furrow extends to the, antapex. Plates bounded by a light colored toothed crest. Thecal surface granular.
Emended description: Lentin and Vozzhennikova, 1990, p.115
Cyst shape subsphaerical to polyhedral; epicyst about 1/3 the length of hypocyst. Autophragm coarsely granulose; ectophragm very thin, porate, appressed to autophragm in intratabular areas; parasutures defined by suturocavate crests which are perforate, margins of the crests are undulose with very long solid, simple acuminate gonal processes, 10-40Ám in length. Paratabulation indicated by parasutural crests and position of gonal processes; formula: 4", 6-7"", 6-7c, 5-6""", 1P (?), 1"""". Archeopyle precingular, Type P (3""only). Paracingulum inticated by six (? seven) elongate rectangular paraplates which are outlined by parasutural crests; paracingulum divided cyst into two unequal parts, epicyst being about 1/3 the length of the hypocyst. Parasulcal area outlined by parasutural crests and may be subdivided by small paraplates. Size: Holotype, diameter 30 µm, width of paracingulum about 5 µm, height of parasutural ridges 3-5 µm. Length of gonal processes 20-35 µm. Range of cyst length 29-32 µm.
Affinities:
Lentin and Vozzhennikova, 1990, p.115: Sokolovidinium spbaericum most closely resembles species of the genus Microdinium. However the distinctive gonal processes and the precingular archeopyle distinguish it from that group. S. sphaericum is very small and the long processes nearly invisible in light microscopy. The orignal description of "toothed crests" on this taxon was a result of distortion of light through the porate sutural crests. The margins of the crests are smooth to slightly undulose. ?Microdinium horridum (Below) Lentin and Williams, 1989 has short gonal processes. However, it is dorsoventrally flattened, has an apical archaeopyle with complex apical paratabulation and two antapical paraplates which are not seen in Sokolovidinium. In addition, because Below only illustrates only exterior morphology of the species M. horridum it is impossible to interpret the nature of the wall structure or suturocavation, if any.