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Elytrocysta brevis
From Fensome et al., 2019:
Elytocysta brevis Stover and Hardenbol, 1994, p.35–36, pl.2, figs.10a–b,11a–b,12. Holotype: Stover and Hardenbol, 1994,
pl.2, figs.10a–b. Age: Rupelian.
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Description
Proximate, subspherical, holocavate cysts with an apical archeopyle which is small relative to the diameter of the bodies. Autophragm about 1 µm thick and bears numerous, short (up to 2 µm long), uniformly distributed, solid projections which are covered distally by a continuous, thin ectophragm. In cross section the projections vary from subcircular to irregularly polygonal and closely adjacent projections may coalesce to form short, discontinuous, usually curved ridges. Archeopyle apical; opercula apparently tetraplacoid and contiguous, although the constituent paraplates are undifferentiated. Opercula mainly secate, but specimens with attached opercula are frequent. Paratabulation expressed by the principal and accessory archeopyle sutures which indicate seven precingular paraplates. The last precingular paraplate is narrow, about as wide as the parasulcal notch; this paraplate may not be separated completely from the operculum. Faint indications of a rather wide, planar paracingulum may be present and the hypocysts lack indications of paratabulation. Size: small to intermediate; cyst diameter 40 to 53 µm and most specimens are less than 50 µm.
Comment
The thin ectophragm may be incomplete on some specimens and on other than well preserved material, may be lacking entirely. The small size of the cysts, the wide planar paracingulum and the presence of seven precingular paraplates suggest that Elytrocysta breva may be allied more closely to Microdinioid genera than to Gonyaulacoid genera with six precingular paraplates.
Comparison
Elytrocysta breva differs from E. druggii Stover and Evitt 1978 by having a thicker autophragm supporting the nontabular projections which appear more variable than those on E. druggii. Although Drugg (1967) described E. druggii (as Membranosphaera maastrichtia) as single layered, he noted (p. 30) that .... "One specimen exhibits remnants of an outer filmy layer supported by the processes."
Types
Holotype: Plate 2, figures 10a-b, Boom Composite Section sample at 3.20 meters.
Paratypes: Plate 2, figures I la-b and 12, Boom Composite Section sample at 9.20 meters.
All types are from the Sint Niklaas locality.
Occurrence
Specimens of Elytrocysta breva occur quite consistently in the Boom Formation from the lowermost sample at the 0.50 meter level (Belsele-Waas Member) to the 29.90 meter level (lower part of the Putte Member). The species is most abundant in samples from and near the S10 horizon. In the Doel 14E- 194 well, Elytrocysta breva is present in all samples.
Elytocysta brevis Stover and Hardenbol, 1994, p.35–36, pl.2, figs.10a–b,11a–b,12. Holotype: Stover and Hardenbol, 1994,
pl.2, figs.10a–b. Age: Rupelian.
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Description
Proximate, subspherical, holocavate cysts with an apical archeopyle which is small relative to the diameter of the bodies. Autophragm about 1 µm thick and bears numerous, short (up to 2 µm long), uniformly distributed, solid projections which are covered distally by a continuous, thin ectophragm. In cross section the projections vary from subcircular to irregularly polygonal and closely adjacent projections may coalesce to form short, discontinuous, usually curved ridges. Archeopyle apical; opercula apparently tetraplacoid and contiguous, although the constituent paraplates are undifferentiated. Opercula mainly secate, but specimens with attached opercula are frequent. Paratabulation expressed by the principal and accessory archeopyle sutures which indicate seven precingular paraplates. The last precingular paraplate is narrow, about as wide as the parasulcal notch; this paraplate may not be separated completely from the operculum. Faint indications of a rather wide, planar paracingulum may be present and the hypocysts lack indications of paratabulation. Size: small to intermediate; cyst diameter 40 to 53 µm and most specimens are less than 50 µm.
Comment
The thin ectophragm may be incomplete on some specimens and on other than well preserved material, may be lacking entirely. The small size of the cysts, the wide planar paracingulum and the presence of seven precingular paraplates suggest that Elytrocysta breva may be allied more closely to Microdinioid genera than to Gonyaulacoid genera with six precingular paraplates.
Comparison
Elytrocysta breva differs from E. druggii Stover and Evitt 1978 by having a thicker autophragm supporting the nontabular projections which appear more variable than those on E. druggii. Although Drugg (1967) described E. druggii (as Membranosphaera maastrichtia) as single layered, he noted (p. 30) that .... "One specimen exhibits remnants of an outer filmy layer supported by the processes."
Types
Holotype: Plate 2, figures 10a-b, Boom Composite Section sample at 3.20 meters.
Paratypes: Plate 2, figures I la-b and 12, Boom Composite Section sample at 9.20 meters.
All types are from the Sint Niklaas locality.
Occurrence
Specimens of Elytrocysta breva occur quite consistently in the Boom Formation from the lowermost sample at the 0.50 meter level (Belsele-Waas Member) to the 29.90 meter level (lower part of the Putte Member). The species is most abundant in samples from and near the S10 horizon. In the Doel 14E- 194 well, Elytrocysta breva is present in all samples.