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Chatangiella porosa
Chatangiella porosa, Marshall, 1988
Holotype: Marshall, 1988, fig.16A-E
Locus typicus: Gippsland Basin, SE Australia
Stratum typicum: Santonian
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Original description: [Marshall, 1988, p. 200]:
Diagnosis:
Ventrodorsal outline elongate, generally subpentagonal. Lateral margins on epicyst tapering towards apex or modified by rounded shoulders on each side of archeopyle. Apex marked by a prominent subconical horn with a truncate tip. Lateral margins on hypocyst tapering towards 2 antapical horns: the left subconical, tip rounded, the right reduced, forming a subconical or rounded projection.
Cysts usually bicavate: narrow pericoels often apparent near equator, especially beneath paracingular ridges. Ventrodorsal endocyst outline subcircular to ovoidal, width usually exceeds length.
Periphragm 0.3-0.5 µm thick, surface smooth, distinctly perforate. Perforations ovoidal to subcircular, 0.5-4.0 µm in maximum dimension, usually appearing irregularly distributed, occasionally arranged in intratabular fields and separated by non-perforate pandasutural bands. On specimens with clearest intratabular fields, only fragments of paraplates discernible, pattern most apparent around equator.
Paracingulum partite, indicated on periphragm by 2 parallel sets of ridges, with smooth to irregular crests, separated by a shallow groove. Archeopyle Type 1 a/?: periarcheopyle stenothetaform to isothetaform, operculum usually attached along posterior margin. Endoarcheopyle often indicated by splits, type uncertain.
Dimensions:
Pericyst length 89 (100) 119 µm, width 59 (66) 79 µm; endocyst length 39 (52) 64 µm, width 54 (63) 76 µm (17 specimens).
Discussion:
The ventrodorsal outlines of the wall layers are variable (Fig.6). Perforation of the periphragm, distinctive of the species, varies in density, only examples with the highest numbers of pores have clear indications that they are arranged in intratabular fields.
Holotype: Marshall, 1988, fig.16A-E
Locus typicus: Gippsland Basin, SE Australia
Stratum typicum: Santonian
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Original description: [Marshall, 1988, p. 200]:
Diagnosis:
Ventrodorsal outline elongate, generally subpentagonal. Lateral margins on epicyst tapering towards apex or modified by rounded shoulders on each side of archeopyle. Apex marked by a prominent subconical horn with a truncate tip. Lateral margins on hypocyst tapering towards 2 antapical horns: the left subconical, tip rounded, the right reduced, forming a subconical or rounded projection.
Cysts usually bicavate: narrow pericoels often apparent near equator, especially beneath paracingular ridges. Ventrodorsal endocyst outline subcircular to ovoidal, width usually exceeds length.
Periphragm 0.3-0.5 µm thick, surface smooth, distinctly perforate. Perforations ovoidal to subcircular, 0.5-4.0 µm in maximum dimension, usually appearing irregularly distributed, occasionally arranged in intratabular fields and separated by non-perforate pandasutural bands. On specimens with clearest intratabular fields, only fragments of paraplates discernible, pattern most apparent around equator.
Paracingulum partite, indicated on periphragm by 2 parallel sets of ridges, with smooth to irregular crests, separated by a shallow groove. Archeopyle Type 1 a/?: periarcheopyle stenothetaform to isothetaform, operculum usually attached along posterior margin. Endoarcheopyle often indicated by splits, type uncertain.
Dimensions:
Pericyst length 89 (100) 119 µm, width 59 (66) 79 µm; endocyst length 39 (52) 64 µm, width 54 (63) 76 µm (17 specimens).
Discussion:
The ventrodorsal outlines of the wall layers are variable (Fig.6). Perforation of the periphragm, distinctive of the species, varies in density, only examples with the highest numbers of pores have clear indications that they are arranged in intratabular fields.