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Elytrocysta breva
Elytocysta breva Stover and Hardenbol, 1994
Elytrocysta breva sp. nov.
Plate 2, Figures 10a- 11 b, l 2
Description
Proximate, subspherical, holocavate cysts with an apical archeopyle which is small relative
to the diameter of the bodies. Autophragm about 1Ám thick and bears numerous, short (up
to 2Ám 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 53Ám and most specimens
are less than 50Ám.
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.
Elytrocysta breva sp. nov.
Plate 2, Figures 10a- 11 b, l 2
Description
Proximate, subspherical, holocavate cysts with an apical archeopyle which is small relative
to the diameter of the bodies. Autophragm about 1Ám thick and bears numerous, short (up
to 2Ám 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 53Ám and most specimens
are less than 50Ám.
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.