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Systematophora placacantha
Systematophora placacantha (Deflandre and Cookson, 1955) Davey et al., 1966; emend. May, 1980
NOW Cleistosphaeridium. Originally Hystrichosphaeridium, subsequently Baltisphaeridium (acritarch), thirdly Impletosphaeridium, fourthly Systematophora, fifthly (and now) Cleistosphaeridium.
Taxonomic junior synonyms: Baltisphaeridium (now Impletosphaeridium) panniforme, according to Sarjeant (1984b, p.86–87) — however, Eaton et al. (2001, p.191) retained Baltisphaeridium panniforme; Systematophora ancyrea, according to Stover and Evitt (1978, p.84) — however, Lentin and Williams (1981, p.272) retained Systematophora ancyrea.
Holotype: Deflandre and Cookson, 1955, pl.9, figs.1–2; Fauconnier and Masure, 2004, pl.76, figs.14–16
Locus typicus: Victoria, Australia
Stratum typicum: Miocene
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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.
Sytematophora placacantha (Deflandre and Cookson, 1955) Davey et al., 1969, has a large number of processes that are aligned so as to divide the whole surface into more or less polygonal fields. Each field is separated from its neighbour by an area devoid of processes. Processes solid, of variable form, somewhat flexuous, simple or branched with pointed or hammer-shaped extremities, widening at the base. Sometimes the bases of 2 or more processes are connected by bridge like strands. Occasionally the apices may coalesce or be connected by a delicate thread as in Cannosphaeropsis. Surface of shell is finely reticulate. Size: Overall: 79-105 µm, without processes: 49-54 µm, process length: 18-31 µm.
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Original diagnosis: Deflandre and Cookson 1955, p.276-277: Hystrichosphaeridium placacanthum
Shell globular, circular or asymmetrical in outline, with a large number of processes that are aligned so as to divide the whole surface into more or less polygonal plate-like areas or fields. Each field is separated from its neighbours by an area devoid of appendages. Processes solid, of variable form, somewhat flexuous, simple or branched with pointed or hammer-shaped extremities, widening at the base. Sometimes the bases of 2 or more processes are connected by bridge-like strands; occasionally the apices may coalesce or be connected by a delicate thread as in Cannosphaeropsis. The fields seem to be of variable size and to have no special equatorial arrangement. The surface of the shell is finely reticulate.
Emended description: May, 1980, p. 68
Cyst spherical to slightly ovoidal, circular in equatorial section, and bilayered. Endophragm appears thicker (ca. 1.0 µm thick) than periphragm (ca. 0.5 µm thick) and is composed of closely arranged bacula imparting a reticulate appearance to the cyst surface. Periphragm smooth, closely appressed to the endophragm, and is formed into sutural folds supporting long, distally bifid spines which outline intratabular fields representing plate equivalents. Spines are flexuous, slender, proximately expanded, simple or branched, and distally bifid. Reflected tabulations 4', 6'', 6c, 5''', 1p, 1'''', 6s. Antapical plate distinctively jellybean-shaped. Cingulum identified by a single row of paired or unpaired spines, with bases elongate in direction of cingulum. Sulcus contains isolated sets of spines representing intratabular plate fields, outlining a posterior sulcal plate, two medial plate pairs, and an anterior sulcal plate. The ps is generally a well-developed plate field. The sulcus lies directly beneath a sulcal notch of the archeopyle. Archeopyle is apical (Type A), formed by the removal of simple, free operculum, corresponding to plates 1', 2', 3' and 4'.
Dimensions: Observed range (33 specimens measured): length main body: 57-63 µm; width: 48-63 µm; spine length: 5-20 µm; wall thickness: ca. 3 µm, endophragm thicker than periphragm.
NOW Cleistosphaeridium. Originally Hystrichosphaeridium, subsequently Baltisphaeridium (acritarch), thirdly Impletosphaeridium, fourthly Systematophora, fifthly (and now) Cleistosphaeridium.
Taxonomic junior synonyms: Baltisphaeridium (now Impletosphaeridium) panniforme, according to Sarjeant (1984b, p.86–87) — however, Eaton et al. (2001, p.191) retained Baltisphaeridium panniforme; Systematophora ancyrea, according to Stover and Evitt (1978, p.84) — however, Lentin and Williams (1981, p.272) retained Systematophora ancyrea.
Holotype: Deflandre and Cookson, 1955, pl.9, figs.1–2; Fauconnier and Masure, 2004, pl.76, figs.14–16
Locus typicus: Victoria, Australia
Stratum typicum: Miocene
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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.
Sytematophora placacantha (Deflandre and Cookson, 1955) Davey et al., 1969, has a large number of processes that are aligned so as to divide the whole surface into more or less polygonal fields. Each field is separated from its neighbour by an area devoid of processes. Processes solid, of variable form, somewhat flexuous, simple or branched with pointed or hammer-shaped extremities, widening at the base. Sometimes the bases of 2 or more processes are connected by bridge like strands. Occasionally the apices may coalesce or be connected by a delicate thread as in Cannosphaeropsis. Surface of shell is finely reticulate. Size: Overall: 79-105 µm, without processes: 49-54 µm, process length: 18-31 µm.
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Original diagnosis: Deflandre and Cookson 1955, p.276-277: Hystrichosphaeridium placacanthum
Shell globular, circular or asymmetrical in outline, with a large number of processes that are aligned so as to divide the whole surface into more or less polygonal plate-like areas or fields. Each field is separated from its neighbours by an area devoid of appendages. Processes solid, of variable form, somewhat flexuous, simple or branched with pointed or hammer-shaped extremities, widening at the base. Sometimes the bases of 2 or more processes are connected by bridge-like strands; occasionally the apices may coalesce or be connected by a delicate thread as in Cannosphaeropsis. The fields seem to be of variable size and to have no special equatorial arrangement. The surface of the shell is finely reticulate.
Emended description: May, 1980, p. 68
Cyst spherical to slightly ovoidal, circular in equatorial section, and bilayered. Endophragm appears thicker (ca. 1.0 µm thick) than periphragm (ca. 0.5 µm thick) and is composed of closely arranged bacula imparting a reticulate appearance to the cyst surface. Periphragm smooth, closely appressed to the endophragm, and is formed into sutural folds supporting long, distally bifid spines which outline intratabular fields representing plate equivalents. Spines are flexuous, slender, proximately expanded, simple or branched, and distally bifid. Reflected tabulations 4', 6'', 6c, 5''', 1p, 1'''', 6s. Antapical plate distinctively jellybean-shaped. Cingulum identified by a single row of paired or unpaired spines, with bases elongate in direction of cingulum. Sulcus contains isolated sets of spines representing intratabular plate fields, outlining a posterior sulcal plate, two medial plate pairs, and an anterior sulcal plate. The ps is generally a well-developed plate field. The sulcus lies directly beneath a sulcal notch of the archeopyle. Archeopyle is apical (Type A), formed by the removal of simple, free operculum, corresponding to plates 1', 2', 3' and 4'.
Dimensions: Observed range (33 specimens measured): length main body: 57-63 µm; width: 48-63 µm; spine length: 5-20 µm; wall thickness: ca. 3 µm, endophragm thicker than periphragm.