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Discorsia nannus
Discorsia nannus (Davey, 1974, p.59, pl.4, figs.9-10) Duxbury, 1977, p.31. Emendations: Duxbury, 1977, p.31 and Khowaja-Ateequzzaman et al., 1985, p.98,100, both as Discorsia nannus.
Originally Oligosphaeridium, subsequently (and now) Discorsia. N.I.A.
Holotype: Davey, 1974, pl.4, fig.9; Fensome et al., 1995, fig.1 - p.1619; Fauconnier and Masure, 2004, pl.22, fig.1.
Locus typicus: Speeton Clay, Speeton, England
Age: Early Barremian.
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Discorsia nannus (Davey, 1974) Duxbury, 1977, emend. Duxbury, 1977, emend. Khowaja-Ateequzzaman et al., 1985. According to Khowaja-Ateequzzaman et al. (1985, p. 98) this is a chorate cyst with subspherical to ellipsoidal body; the periphragm is striate, giving rise to 18-20 tubiform, distally flared, intratabular striate processes. Process formula is 4', 6", (as), 0c, 5-6"’, ps, 1p, 1"”. Apical archeopyle. Size: from Duxbury, main body 22-35 x 19-27 µm, overall 41-57 x 32-54 µm, process length from Davey (1974), 10-14 µm.
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Original description: Davey, 1974, p. 59: Oligosphaeridium nannum
Diagnosis: The central body is small (usually under 25 Ám diameter), subspherical and bears a low number of processes (usually 13 or 14). The processes are all of similar size; they expand both proximally and distally, and terminate distally with a gently denticulate margin. Each has strong longitudinal ribs which radiate from the process base onto the cyst surface and may join with similar ribs radiating from neighbouring processes. Two or three of the processes may be linked medially by a fine membrane. An archaeopyle has not been observed with certainty and for this reason it is probably small.
Dimensions: holotype: central body diameter, 24x24 Ám, process length, 10-14 Ám. Range: central body diameter, 17(22)24 Ám, process length, 12-14 Ám (maximum).
Emended diagnosis: Duxbury, 1977, p. 31: Discorsia nanna
A small chorate cyst. Endophragm smooth to finely granular, inner body ovoidal, longer than broad, with the epitract smaller and less rounded than the hypotract. Periphragm produced into 15 hollow, proximally and distally flaring processes. These are distally denticulate and intratabular, one per reflected plate area indicating a tabulation pattern 1', 6'', 6''', 1p, 1''''. All processes bear longitudinal cord-like thickenings which extend onto the body surface and may join with those from neighbouring processes. The cingular zone is free of processes and the epitractal processes are generally smaller than the hypotractal ones. Archeopyle apical, formed by loss of plate 1'.
Dimensions: Main body 35(28)22 x 27(23)19 Ám. Overall 57(50)41x54(43)32 Ám.
15 specimens measured.
Emended description: Khowaja-Ateequzzaman et al., 1985, p. 98-100
Diagnosis: Cysts chorate, body subspherical to ellipsoidal; periphragm striate, giving rise to 18-20 tubiform, distally flared, intratabular, striate processes.
Process formula 4', 6'', (as), 0c, 5-6''', ps, 1p, 1''''. Archeopyle apical (tA).
Description: Cyst wall double, appressed between processes, endophragm thin and smooth, periphragm appears thicker than endophragm due to striate nature; striations may be faint on body wall radiating from process bases, but prominent on processes, parallel throughout process length; processes intratabular, tubiform, denticulate, variable in length and breadth; process formula 4', 6'', (as), 5-6''', ps, 1p, 1''''; cingular processes always absent. Apical processes slender, 2nd and 6th precingulars usually broader than other precingulars; hypocyst processes not very different in size. A thin membrane often connects the base of the antapical and a few other processes on the hypocyst. Archeopyle apical, made up of four paraplates as indicated by processes, operculum occasionally attached and may show indications of being compound (Plate 4, figs. 2-4).
Dimensions: Holotype: central body 24x24 Ám, processes10-14 Ám long. Indian specimens 921 measured): central body 32-46x24-31 Ám, process length 6-17 Ám.
Affinities:
Davey, 1974, p. 59
The overall small size, ribbed processes and central body surface easily distinguish O. nannum sp. nov. from all previously described species.
It is placed in Oligosphaeridium because of the number of processes present. However, it is considered that this species affinities may lie with the genus Kleithriasphaeridium, especially with K. corrugatum.
Khowaja-Ateequzzaman et al., 1985, p. 100
Discorsia difers from Oligosphaeridium in that it possesses striate processes and body surface, and possibly a compound operculum.
Originally Oligosphaeridium, subsequently (and now) Discorsia. N.I.A.
Holotype: Davey, 1974, pl.4, fig.9; Fensome et al., 1995, fig.1 - p.1619; Fauconnier and Masure, 2004, pl.22, fig.1.
Locus typicus: Speeton Clay, Speeton, England
Age: Early Barremian.
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Discorsia nannus (Davey, 1974) Duxbury, 1977, emend. Duxbury, 1977, emend. Khowaja-Ateequzzaman et al., 1985. According to Khowaja-Ateequzzaman et al. (1985, p. 98) this is a chorate cyst with subspherical to ellipsoidal body; the periphragm is striate, giving rise to 18-20 tubiform, distally flared, intratabular striate processes. Process formula is 4', 6", (as), 0c, 5-6"’, ps, 1p, 1"”. Apical archeopyle. Size: from Duxbury, main body 22-35 x 19-27 µm, overall 41-57 x 32-54 µm, process length from Davey (1974), 10-14 µm.
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Original description: Davey, 1974, p. 59: Oligosphaeridium nannum
Diagnosis: The central body is small (usually under 25 Ám diameter), subspherical and bears a low number of processes (usually 13 or 14). The processes are all of similar size; they expand both proximally and distally, and terminate distally with a gently denticulate margin. Each has strong longitudinal ribs which radiate from the process base onto the cyst surface and may join with similar ribs radiating from neighbouring processes. Two or three of the processes may be linked medially by a fine membrane. An archaeopyle has not been observed with certainty and for this reason it is probably small.
Dimensions: holotype: central body diameter, 24x24 Ám, process length, 10-14 Ám. Range: central body diameter, 17(22)24 Ám, process length, 12-14 Ám (maximum).
Emended diagnosis: Duxbury, 1977, p. 31: Discorsia nanna
A small chorate cyst. Endophragm smooth to finely granular, inner body ovoidal, longer than broad, with the epitract smaller and less rounded than the hypotract. Periphragm produced into 15 hollow, proximally and distally flaring processes. These are distally denticulate and intratabular, one per reflected plate area indicating a tabulation pattern 1', 6'', 6''', 1p, 1''''. All processes bear longitudinal cord-like thickenings which extend onto the body surface and may join with those from neighbouring processes. The cingular zone is free of processes and the epitractal processes are generally smaller than the hypotractal ones. Archeopyle apical, formed by loss of plate 1'.
Dimensions: Main body 35(28)22 x 27(23)19 Ám. Overall 57(50)41x54(43)32 Ám.
15 specimens measured.
Emended description: Khowaja-Ateequzzaman et al., 1985, p. 98-100
Diagnosis: Cysts chorate, body subspherical to ellipsoidal; periphragm striate, giving rise to 18-20 tubiform, distally flared, intratabular, striate processes.
Process formula 4', 6'', (as), 0c, 5-6''', ps, 1p, 1''''. Archeopyle apical (tA).
Description: Cyst wall double, appressed between processes, endophragm thin and smooth, periphragm appears thicker than endophragm due to striate nature; striations may be faint on body wall radiating from process bases, but prominent on processes, parallel throughout process length; processes intratabular, tubiform, denticulate, variable in length and breadth; process formula 4', 6'', (as), 5-6''', ps, 1p, 1''''; cingular processes always absent. Apical processes slender, 2nd and 6th precingulars usually broader than other precingulars; hypocyst processes not very different in size. A thin membrane often connects the base of the antapical and a few other processes on the hypocyst. Archeopyle apical, made up of four paraplates as indicated by processes, operculum occasionally attached and may show indications of being compound (Plate 4, figs. 2-4).
Dimensions: Holotype: central body 24x24 Ám, processes10-14 Ám long. Indian specimens 921 measured): central body 32-46x24-31 Ám, process length 6-17 Ám.
Affinities:
Davey, 1974, p. 59
The overall small size, ribbed processes and central body surface easily distinguish O. nannum sp. nov. from all previously described species.
It is placed in Oligosphaeridium because of the number of processes present. However, it is considered that this species affinities may lie with the genus Kleithriasphaeridium, especially with K. corrugatum.
Khowaja-Ateequzzaman et al., 1985, p. 100
Discorsia difers from Oligosphaeridium in that it possesses striate processes and body surface, and possibly a compound operculum.