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Perisseiasphaeridium
From Williams et al., 2017:
[Perisseiasphaeridium, Davey and Williams, 1966b, p. 78
Type species: Perisseiasphaeridium pannosum, Davey and Williams, 1966b (pl.11, fig.8)]
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Original description: [Davey and Williams, 1966]:
Description:
Chorate cysts with sub-spherical central body composed of two membranes. Process of two types: (i) larger, tubiform, open distally and intratabular; one process per plate area, and (ii) smaller, closed processes restricted to sulcal and cingular regions. Tabulation reflected by tubiform processes 4`, 6", 5```, 1p, 1````. Archaeopyle apical.
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Modified description:
Stover and Evitt, 1978, p. 73-75:
Synopsis:
Cysts skolochorate, gonyaulacacean; body subspherical with hollow, complexly branched, intratabular processes and slender, apparently solid processes in paracingular and parasulcal areas; archeopyle apical, Type (tA).
Description:
Shape: Body subspherical.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Processes intratabular, larger ones hollow; distal half of each process complexly branched; simple, slender, apparently solid processes in paracingular and parasulcal areas. Autophragm between processes smooth to scabrate.
Paratabulation: Indicated by intratabular processes; gonyaulacacean, process formula: 4`, 6", ?c, 5-6```, lp, 1````, ?s.
Archeopyle: Apical, Type (tA), operculum free. Configuration of operculum unknown, presumed to be approximately equidimensional and to conform with zigzag outline of principal archeopyle suture.
Paracingulum: Poorly indicated by the presence of slender, apparently solid processes; exact number of processes undetermined.
Parasulcus: Same indications as those of paracingulum.
Size: Intermediate to large.
Affinities:
Perisseiasphaeridium differs from Hystrichosphaeridium in having complexly branched processes. It differs from Oligosphaeridium in having paracingular processes. Perisseiasphaeridium is most similar to Hystrichosphaerina from which it differs in not having ring trabeculae at the distal ends of nonparacingular processes.
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Poulsen, 1996, p. 64:
Amphorula-Pensseiasphaeridium-Systematophora complex:
Discussion:
The species included within these three genera have a combination of intratabular annulate-arcuate ridges or processes, or large, often deeply digitate processes in the precingular and postcingular paraplate series, and solid cingular processes linked in pairs by a low ridge. Generic differentiation depends on ridge/process morphology, i.e. annulate to arcuate septa in Amphorula; annulate to arcuate complexes composed of simple to complex-linked processes in Systematophora; and tubiform, simple to deeply digitate and fenestrate processes in Perisseiasphaeridium. However, some specimens of Systematophora areolata have processes reduced in length, showing the relationship with Amphorula. In contrast, when the processes of Systematophora are long and the annulate complex becomes narrow at the base, these process complexes are very similar to the processes of, for example, Perisseiasphaeridium pannosum. In one specimen (Pl. 30, Fig. 6), the process complexes on the epicyst are of the Systematophora areolata type, whereas the tubiform processes on the hypocyst are of P. pannosum type.
The Amphorula-Perisseiasphaeridium-Systematophora complex is not considered to be a simple lineage. Davey (1982) regarded Systematophora as the root stock from which early members of the other genera evolved, whereas Stancliffe and Sarjeant (1990) believed that Oligosphaeridium descended from Systematophora, and that Amphorula descended from Taeniophora and Rigaudella and, that both Systematophora and Rigaudella descended from Adnatosphaeridium. Personally, I believe it is more likely that Amphorula descended from Systematophora. Some of the ideas are summarized on Text-Fig. 20, though interrelationships are complex and not fully understood.
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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.
Perisseiasphaeridium Davey and Williams, 1966b. Stover and Evitt (1978, p.73) provided the following synopsis for Perisseiasphaeridium . Cysts skolochorate, gonyaulacacean; body subspherical with hollow, complexly branched, intratabular processes and slender, apparently solid processes in paracingular and parasulcal areas, archeopyle apical, type tA.
[Perisseiasphaeridium, Davey and Williams, 1966b, p. 78
Type species: Perisseiasphaeridium pannosum, Davey and Williams, 1966b (pl.11, fig.8)]
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Original description: [Davey and Williams, 1966]:
Description:
Chorate cysts with sub-spherical central body composed of two membranes. Process of two types: (i) larger, tubiform, open distally and intratabular; one process per plate area, and (ii) smaller, closed processes restricted to sulcal and cingular regions. Tabulation reflected by tubiform processes 4`, 6", 5```, 1p, 1````. Archaeopyle apical.
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Modified description:
Stover and Evitt, 1978, p. 73-75:
Synopsis:
Cysts skolochorate, gonyaulacacean; body subspherical with hollow, complexly branched, intratabular processes and slender, apparently solid processes in paracingular and parasulcal areas; archeopyle apical, Type (tA).
Description:
Shape: Body subspherical.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Processes intratabular, larger ones hollow; distal half of each process complexly branched; simple, slender, apparently solid processes in paracingular and parasulcal areas. Autophragm between processes smooth to scabrate.
Paratabulation: Indicated by intratabular processes; gonyaulacacean, process formula: 4`, 6", ?c, 5-6```, lp, 1````, ?s.
Archeopyle: Apical, Type (tA), operculum free. Configuration of operculum unknown, presumed to be approximately equidimensional and to conform with zigzag outline of principal archeopyle suture.
Paracingulum: Poorly indicated by the presence of slender, apparently solid processes; exact number of processes undetermined.
Parasulcus: Same indications as those of paracingulum.
Size: Intermediate to large.
Affinities:
Perisseiasphaeridium differs from Hystrichosphaeridium in having complexly branched processes. It differs from Oligosphaeridium in having paracingular processes. Perisseiasphaeridium is most similar to Hystrichosphaerina from which it differs in not having ring trabeculae at the distal ends of nonparacingular processes.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Poulsen, 1996, p. 64:
Amphorula-Pensseiasphaeridium-Systematophora complex:
Discussion:
The species included within these three genera have a combination of intratabular annulate-arcuate ridges or processes, or large, often deeply digitate processes in the precingular and postcingular paraplate series, and solid cingular processes linked in pairs by a low ridge. Generic differentiation depends on ridge/process morphology, i.e. annulate to arcuate septa in Amphorula; annulate to arcuate complexes composed of simple to complex-linked processes in Systematophora; and tubiform, simple to deeply digitate and fenestrate processes in Perisseiasphaeridium. However, some specimens of Systematophora areolata have processes reduced in length, showing the relationship with Amphorula. In contrast, when the processes of Systematophora are long and the annulate complex becomes narrow at the base, these process complexes are very similar to the processes of, for example, Perisseiasphaeridium pannosum. In one specimen (Pl. 30, Fig. 6), the process complexes on the epicyst are of the Systematophora areolata type, whereas the tubiform processes on the hypocyst are of P. pannosum type.
The Amphorula-Perisseiasphaeridium-Systematophora complex is not considered to be a simple lineage. Davey (1982) regarded Systematophora as the root stock from which early members of the other genera evolved, whereas Stancliffe and Sarjeant (1990) believed that Oligosphaeridium descended from Systematophora, and that Amphorula descended from Taeniophora and Rigaudella and, that both Systematophora and Rigaudella descended from Adnatosphaeridium. Personally, I believe it is more likely that Amphorula descended from Systematophora. Some of the ideas are summarized on Text-Fig. 20, though interrelationships are complex and not fully understood.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Perisseiasphaeridium Davey and Williams, 1966b. Stover and Evitt (1978, p.73) provided the following synopsis for Perisseiasphaeridium . Cysts skolochorate, gonyaulacacean; body subspherical with hollow, complexly branched, intratabular processes and slender, apparently solid processes in paracingular and parasulcal areas, archeopyle apical, type tA.