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Cleistosphaeridium placacanthum
From Fensome et al., 2019:
Cleistosphaeridium placacanthum (Deflandre and Cookson, 1955, p.276–277, pl.9, figs.1–3) Eaton et al., 2001, p.190. Emendation: May, 1980, p.68, as Systematophora placacantha. Holotype: Deflandre and Cookson, 1955, pl.9, figs.1–2;
Fauconnier and Masure, 2004, pl.76, figs.14–16. Originally Hystrichosphaeridium, subsequently Baltisphaeridium
(Appendix A), 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 (as and now
Impletosphaeridium) panniforme; Systematophora ancyrea, according to Stover and Evitt (1978, p.84) — however,
Lentin and Williams (1981, p.272) retained Systematophora ancyrea. Age: Miocene.
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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.
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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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[Remarks from Eaton et al., 2001, p. 190]:
Remarks: For a comparison between Cleistosphaeridium placacanthum and other species here assigned to the genus Cleistosphaeridium, see Remarks under Cleistosphaeridium diversispinosum.
DEFLANDRE & COOKSON'S original illustrations of Hystrichosphaeridium placacanthum clearly show the features here considered diagnostic of Cleistosphaeridium. In the holotype (their pI. 9, figs. 1-2) many of the processes are simple, but there is still considerable variation in form, including the characteristic dolabrate type (described as "harnmer-shaped" by DEFLANDRE & COOKSON). Their second illustrated specimen (pI. 9, fig. 3) exhibits numerous "bridging" structures which link adjacent processes at an intermediate point along their length. This second specimen is in polar view, and shows some degree of dorso-ventral flattening , while the form of its archeopyle (apparently on the lower surface) is closely comparable to that of Cleistosphaeridium diversispinosum, as described herein. DEFLANDRE & COOKSON al so recognized some distal linkage between processes. However, Cleistosphaeridium placacanthum differs from Cleistosphaeridium diversispinosum in that the majority, or all, of its processes are arranged in clearly defined penitabular process complexes. These are emphasized by the extensive development of basal ridges (DEFLANDRE & COOKSON, 1955, pI. 9, figs. 1-2).
We do not accept the emended description provided by MAY (1980, p. 68, pI. 7, figs. 8-11). His emendation was based on specimens from Upper Cretaceous (Lower Maastrichtian) sediments in New Jersey, USA, which show a comprehensive development of penitabular complexes, but whose processes seem more closely related to those of the Areoligera senonensis group. SARJEANT (1984, p. 87) also recorded strong doubts that MAY'S emendation could be applied to the type material of Cleistosphaeridium placacanthum. Similar material to MAY'S, from about the same age, was described by MARHEINECKE (1986, pI. 4, fig. 1, pI. 12, figs.3-5 ; 1992, p.66, pI. 12, figs.7-9) from Late Maastrichtian strata in Germany and by OBOH-lKUENOBE et al. (1998, pI. 3, fig. 8) from Maastrichtian strata from offshore west Africa. We suggest that this material may represent a distinct species group, unrelated to Cleistosphaeridium. Similarly, we are not convinced that Baltisphaeridium panniforme GERLACH 1961 from Middle Miocene sediments in Germany, is a junior taxonomic synonym of Cleistosphaeridium placacanthum, as was suggested by SARJEANT (1984, p. 87). In GERLACH'S original illustration of the holotype (pI. 28, fig. 13), the processes are not obviously arranged in penitabular complexes, and there is no evidence of basal ridges. It is possible that this specimen is a marginate cyst of the Chiropteridium type. According to SARJEANT, it has deteriorated to such an extent that it is now unrecognizable, but the lectotype selected by SARJEANT (1984, pI. 3, fig. 1) does not display the characteristic process type or process distribution of Cleistosphaeridium placacanthum, and its affinity (and therefore that of Baltisphaeridium panniforme) remains uncertain.
Age: Based on illustrated records, the confirmed range of Cleistosphaeridium placacanthum is Mid Eocene to Late Miocene (Table 2). From the records listed, this species appears to be most common in Oligocene to Mid Miocene strata.
Cleistosphaeridium placacanthum (Deflandre and Cookson, 1955, p.276–277, pl.9, figs.1–3) Eaton et al., 2001, p.190. Emendation: May, 1980, p.68, as Systematophora placacantha. Holotype: Deflandre and Cookson, 1955, pl.9, figs.1–2;
Fauconnier and Masure, 2004, pl.76, figs.14–16. Originally Hystrichosphaeridium, subsequently Baltisphaeridium
(Appendix A), 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 (as and now
Impletosphaeridium) panniforme; Systematophora ancyrea, according to Stover and Evitt (1978, p.84) — however,
Lentin and Williams (1981, p.272) retained Systematophora ancyrea. Age: Miocene.
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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.
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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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[Remarks from Eaton et al., 2001, p. 190]:
Remarks: For a comparison between Cleistosphaeridium placacanthum and other species here assigned to the genus Cleistosphaeridium, see Remarks under Cleistosphaeridium diversispinosum.
DEFLANDRE & COOKSON'S original illustrations of Hystrichosphaeridium placacanthum clearly show the features here considered diagnostic of Cleistosphaeridium. In the holotype (their pI. 9, figs. 1-2) many of the processes are simple, but there is still considerable variation in form, including the characteristic dolabrate type (described as "harnmer-shaped" by DEFLANDRE & COOKSON). Their second illustrated specimen (pI. 9, fig. 3) exhibits numerous "bridging" structures which link adjacent processes at an intermediate point along their length. This second specimen is in polar view, and shows some degree of dorso-ventral flattening , while the form of its archeopyle (apparently on the lower surface) is closely comparable to that of Cleistosphaeridium diversispinosum, as described herein. DEFLANDRE & COOKSON al so recognized some distal linkage between processes. However, Cleistosphaeridium placacanthum differs from Cleistosphaeridium diversispinosum in that the majority, or all, of its processes are arranged in clearly defined penitabular process complexes. These are emphasized by the extensive development of basal ridges (DEFLANDRE & COOKSON, 1955, pI. 9, figs. 1-2).
We do not accept the emended description provided by MAY (1980, p. 68, pI. 7, figs. 8-11). His emendation was based on specimens from Upper Cretaceous (Lower Maastrichtian) sediments in New Jersey, USA, which show a comprehensive development of penitabular complexes, but whose processes seem more closely related to those of the Areoligera senonensis group. SARJEANT (1984, p. 87) also recorded strong doubts that MAY'S emendation could be applied to the type material of Cleistosphaeridium placacanthum. Similar material to MAY'S, from about the same age, was described by MARHEINECKE (1986, pI. 4, fig. 1, pI. 12, figs.3-5 ; 1992, p.66, pI. 12, figs.7-9) from Late Maastrichtian strata in Germany and by OBOH-lKUENOBE et al. (1998, pI. 3, fig. 8) from Maastrichtian strata from offshore west Africa. We suggest that this material may represent a distinct species group, unrelated to Cleistosphaeridium. Similarly, we are not convinced that Baltisphaeridium panniforme GERLACH 1961 from Middle Miocene sediments in Germany, is a junior taxonomic synonym of Cleistosphaeridium placacanthum, as was suggested by SARJEANT (1984, p. 87). In GERLACH'S original illustration of the holotype (pI. 28, fig. 13), the processes are not obviously arranged in penitabular complexes, and there is no evidence of basal ridges. It is possible that this specimen is a marginate cyst of the Chiropteridium type. According to SARJEANT, it has deteriorated to such an extent that it is now unrecognizable, but the lectotype selected by SARJEANT (1984, pI. 3, fig. 1) does not display the characteristic process type or process distribution of Cleistosphaeridium placacanthum, and its affinity (and therefore that of Baltisphaeridium panniforme) remains uncertain.
Age: Based on illustrated records, the confirmed range of Cleistosphaeridium placacanthum is Mid Eocene to Late Miocene (Table 2). From the records listed, this species appears to be most common in Oligocene to Mid Miocene strata.