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Discorsia
From Fensome et al., 2019:
Discorsia, Duxbury, 1977, p.30.
Emendation: Khowaja-Ateequzzaman et al., 1985, p.98.
Type: Davey, 1974, pl.4, fig.9, as Oligosphaeridium nannus.
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Original description: [Duxbury, 1977]:
Description:
Chorate cysts bearing 15 plate-centred, striate processes reflecting the tabulation 1`, 6``, 6```, 1p, 1````. Main body ovoidal, epitract smaller and less
rounded than hypotract. Processes variable in size; the apical process is small, the precingular processes somewhat larger and the postcingular and antapical processes are the largest of all. Archeopyle apical, formed by loss of plate 1`.
Affinities:
In possessing a small number of plate-centered processes, Discorsia resembles Oligosphaeridium Davey and Williams, 1966. The various sizes of processes on each specimen and the single-plate apical archaeopyle of Discorsia contrasts with the approximately equal-sizes processes and tetratabular archaeopyle of Oligosphaeridium. Discorsia differs from Cordosphaeridium (Eisenack, 1963) Davey, 1969 in its apical archaeopyle (Cordosphaeridium possesses a precingular one) and in the lack of any cingular processes. Also, the body surface of Discorsia is smooth to finely granular and bears no resemblance to the fibrous and pitted surface of Cordosphaeridium.
Discorsia bears some resemblance to Kleithriasphaeridium Davey, 1974. The main differences between the two are the archaeopyle type (apical in Discorsia and precingular in Kleithriasphaeridium) and the number of processes, with Kleithriasphaeridium having 21-23 as opposed to the 15 of Discorsia. Also, Discorsia nanna, the type species of the genus, is considerably smaller than any described species of Kleithriasphaeridium.
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Emended description:
Khowaja-Ateequzzaman et al., 1985:
Description:
Cyst chorate, body subspherical to ellipsoidal, periphragm striate with intratabular, striate, tubiform processes. Process formula 4`, 6``(as), 0c, 5-6```, ps, 1p, 1````. Archeopyle apical (tA).
Affinities:
Discorsia equals Oligosphaeridium in its overall process distribution and the absence of cingular processes, but differs in the striate (fibrous) nature of the processes and periphragm surface. It remains uncertain whether the operculum is simple or compound, though there is an indication of separation into individual paraplates.
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Modified description:
Stover and Williams 1987, p. 83
Synopsis:
Cysts skolochorate, body subspherical to ellipsoidal and bears 19 to 20 intratabular, striate, hollow, distally open processes of variable size; paratabulation gonyaulacacean formula: 4`, 6``, 0c, 5-6```, 1p, 1````, Xs; archeopyle apical.
Description:
Shape: Body subspherical to ellipsoidal.
Wall relationships: Endophragm and striate periphragm appressed between processes.
Wall features: No parasutural features. Intratabular processes hollow, longitudinally striate, open distally; no cingular processes.
Archeopyle: Apical, type [4A], free opercula not observed.
Paratabulation: Indicated by intratabular processes; process formula: 4`, 6``, 0c, 5-6```,1 p, 1````; Xs.
Paracingulum: Indicated by absence of processes in the equatorial area.
Parasulcus: Apparently not indicated.
Size: Small, 30 to 40 µm.
Affinities:
Discorsia differs from Oligosphaeridium Davey and Williams in Davey et al. 1966 in having a striate periphragm and processes, and from Bourkidinium Morgan 1975 in having pre- and postcingular processes. On Bourkidinium the processes are restricted to the polar areas.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Discorsia Duxbury, 1977. Stover and Williams (1987, p.83) provided the following synopsis. Cysts skolochorate, body subspherical to ellipsoidal and bears 19-20 intratabular, striate, hollow, distally open processes of variable size. Paratabulation gonyaulacacean formula 4`, 6", 0c, 5-6". 1p, 1" , xs. Archeopyle apical.
Discorsia, Duxbury, 1977, p.30.
Emendation: Khowaja-Ateequzzaman et al., 1985, p.98.
Type: Davey, 1974, pl.4, fig.9, as Oligosphaeridium nannus.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Duxbury, 1977]:
Description:
Chorate cysts bearing 15 plate-centred, striate processes reflecting the tabulation 1`, 6``, 6```, 1p, 1````. Main body ovoidal, epitract smaller and less
rounded than hypotract. Processes variable in size; the apical process is small, the precingular processes somewhat larger and the postcingular and antapical processes are the largest of all. Archeopyle apical, formed by loss of plate 1`.
Affinities:
In possessing a small number of plate-centered processes, Discorsia resembles Oligosphaeridium Davey and Williams, 1966. The various sizes of processes on each specimen and the single-plate apical archaeopyle of Discorsia contrasts with the approximately equal-sizes processes and tetratabular archaeopyle of Oligosphaeridium. Discorsia differs from Cordosphaeridium (Eisenack, 1963) Davey, 1969 in its apical archaeopyle (Cordosphaeridium possesses a precingular one) and in the lack of any cingular processes. Also, the body surface of Discorsia is smooth to finely granular and bears no resemblance to the fibrous and pitted surface of Cordosphaeridium.
Discorsia bears some resemblance to Kleithriasphaeridium Davey, 1974. The main differences between the two are the archaeopyle type (apical in Discorsia and precingular in Kleithriasphaeridium) and the number of processes, with Kleithriasphaeridium having 21-23 as opposed to the 15 of Discorsia. Also, Discorsia nanna, the type species of the genus, is considerably smaller than any described species of Kleithriasphaeridium.
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Emended description:
Khowaja-Ateequzzaman et al., 1985:
Description:
Cyst chorate, body subspherical to ellipsoidal, periphragm striate with intratabular, striate, tubiform processes. Process formula 4`, 6``(as), 0c, 5-6```, ps, 1p, 1````. Archeopyle apical (tA).
Affinities:
Discorsia equals Oligosphaeridium in its overall process distribution and the absence of cingular processes, but differs in the striate (fibrous) nature of the processes and periphragm surface. It remains uncertain whether the operculum is simple or compound, though there is an indication of separation into individual paraplates.
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Modified description:
Stover and Williams 1987, p. 83
Synopsis:
Cysts skolochorate, body subspherical to ellipsoidal and bears 19 to 20 intratabular, striate, hollow, distally open processes of variable size; paratabulation gonyaulacacean formula: 4`, 6``, 0c, 5-6```, 1p, 1````, Xs; archeopyle apical.
Description:
Shape: Body subspherical to ellipsoidal.
Wall relationships: Endophragm and striate periphragm appressed between processes.
Wall features: No parasutural features. Intratabular processes hollow, longitudinally striate, open distally; no cingular processes.
Archeopyle: Apical, type [4A], free opercula not observed.
Paratabulation: Indicated by intratabular processes; process formula: 4`, 6``, 0c, 5-6```,1 p, 1````; Xs.
Paracingulum: Indicated by absence of processes in the equatorial area.
Parasulcus: Apparently not indicated.
Size: Small, 30 to 40 µm.
Affinities:
Discorsia differs from Oligosphaeridium Davey and Williams in Davey et al. 1966 in having a striate periphragm and processes, and from Bourkidinium Morgan 1975 in having pre- and postcingular processes. On Bourkidinium the processes are restricted to the polar areas.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Discorsia Duxbury, 1977. Stover and Williams (1987, p.83) provided the following synopsis. Cysts skolochorate, body subspherical to ellipsoidal and bears 19-20 intratabular, striate, hollow, distally open processes of variable size. Paratabulation gonyaulacacean formula 4`, 6", 0c, 5-6". 1p, 1" , xs. Archeopyle apical.