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Australisphaera
From Williams et al., 2017:
[Australisphaera, Davey, 1978, p. 892; Emendations: Duxbury, 1983, p. 25; Harding, 1986a, p. 100
however, see Harding (1990b, p.21)
Type species: Australisphaera verrucosa, Davey, 1978 (pl.2, fig.1)]
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Original description: [Davey, 1978]:
Diagnosis:
The cyst is dorso-ventrally flattened and has a subpolygonal outline; the hypotract is slightly asymmetric. A single antapical and two lateral features, developed as a relatively high ornament or low to high horns, are present. The ornament is low and high spines or processes are absent. The archeopyle is apical with a slightly to moderately zig-zag margin; the sulcal notch is offset to the left of the midline.
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Emended descriptions:
Duxbury, 1983:
Diagnosis:
Proximate, ceratiacean dinoflagellate cysts which are single-walled dorso-ventrally flattened and have lateral and antapical features developed as unusually high ornament or low to high, hollow, distally closed horns. Overall, the ornament may be low, but spines may occur, usually concentrated at horn terminations, sometimes extending the horns considerably. Vague paratabulation may be indicated by ornament alignment. The archeopyle is apical with a zig-zag margin and the parasulcus is offset to the left of the mid-line.
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Harding, 1986:
Diagnosis:
Shape: ceratioid. Rhomboidal with a blunt apical, two cingular and two unequally developed antapical horns (the left being longer). The apical and cingular horns are often poorly developed and only expressed as `lobes`. Strong dorsoventral flattening.
Phragma: very thin to moderate thickness (0.5-1.5 µm). Wall is two layered, consisting of an unornamented `endocyst` and an ornamented pericyst of equal thicknesses. The two layers are closely adpressed throughout and can only be resolved clearly by electron microscopy. The non-tabular ornamentation varies from low, widely spaced verrucae to densely packed echinae or large tubercles.
Paratabulation: indicated only by archaeopyle suture and paracingulum.
Archaeopyle: apical, type (tA). Principal archaeopyle suture moderately zigzag- operculum free.
Paracingulum: not always developed. When present, most noticeable in lateral regions-cingular horns appear notched.
Parasulcus: rarely observed. Marked by an antapical arcuate depression.
Harding, 1990, questioned the emendation of Australisphaera by Harding, 1986 however, see Harding (1990b, p.21).
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Modified description:
Stover and Williams, 1987, p. 31:
Synopsis:
Cysts proximate, autophragm lenticular, with one or two antapical and two lateral lobes or horns, additional lobes or horns may be present, autophragm ornamented with features of low relief, archeopyle apical, probably type (tA); operculum free, offset parasulcal notch poorly developed. Isolated opercula and complete specimens have not been identified.
Description:
Shape: Lenticular, outline subpolygonal; an antapical and two lateral variably developed protrusions usually present; additional protrusions may be present Outline of apex unknown.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Autophragm with features of low relief to spinose.
Archeopyle: Apical, probably type [tA]; operculum free; in-place or free opercula not observed.
Paratabulation: Generally indicated by archeopyle only; other features faint or inconsistently developed.
Paracingulum: Possibly indicated by two lateral projections posterior to archeopyle margins.
Parasulcus: Not indicated; offset parasulcal notch not a conspicuous feature.
Size: Intermediate to large, about 60 µm to 140 µm in width.
Affinities:
Australisphaera differs from Canningia Cookson and Eisenack 1960 emended Below 1981 in having a single rather than two wall layers and forms of Australisphaera, which possess two lateral and two antapical horns, differ from Muderongia Cookson and Eisenack 1958 in being acavate. The latter difference applies also to the dinoflagellates identified as "Muderongia" sp. A of Nichols and Jacobson (1982). Cyclonephelium Deflandre and Cookson 1955 emended Sarjeant and Stover 1978 differs from Australisphaera in having more prominent ornamentation and in lacking lateral lobes; however, Cyclonephelium may have one or two antapical lobes, but not antapical horns.
[Australisphaera, Davey, 1978, p. 892; Emendations: Duxbury, 1983, p. 25; Harding, 1986a, p. 100
however, see Harding (1990b, p.21)
Type species: Australisphaera verrucosa, Davey, 1978 (pl.2, fig.1)]
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Original description: [Davey, 1978]:
Diagnosis:
The cyst is dorso-ventrally flattened and has a subpolygonal outline; the hypotract is slightly asymmetric. A single antapical and two lateral features, developed as a relatively high ornament or low to high horns, are present. The ornament is low and high spines or processes are absent. The archeopyle is apical with a slightly to moderately zig-zag margin; the sulcal notch is offset to the left of the midline.
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Emended descriptions:
Duxbury, 1983:
Diagnosis:
Proximate, ceratiacean dinoflagellate cysts which are single-walled dorso-ventrally flattened and have lateral and antapical features developed as unusually high ornament or low to high, hollow, distally closed horns. Overall, the ornament may be low, but spines may occur, usually concentrated at horn terminations, sometimes extending the horns considerably. Vague paratabulation may be indicated by ornament alignment. The archeopyle is apical with a zig-zag margin and the parasulcus is offset to the left of the mid-line.
-------------------------------------------
Harding, 1986:
Diagnosis:
Shape: ceratioid. Rhomboidal with a blunt apical, two cingular and two unequally developed antapical horns (the left being longer). The apical and cingular horns are often poorly developed and only expressed as `lobes`. Strong dorsoventral flattening.
Phragma: very thin to moderate thickness (0.5-1.5 µm). Wall is two layered, consisting of an unornamented `endocyst` and an ornamented pericyst of equal thicknesses. The two layers are closely adpressed throughout and can only be resolved clearly by electron microscopy. The non-tabular ornamentation varies from low, widely spaced verrucae to densely packed echinae or large tubercles.
Paratabulation: indicated only by archaeopyle suture and paracingulum.
Archaeopyle: apical, type (tA). Principal archaeopyle suture moderately zigzag- operculum free.
Paracingulum: not always developed. When present, most noticeable in lateral regions-cingular horns appear notched.
Parasulcus: rarely observed. Marked by an antapical arcuate depression.
Harding, 1990, questioned the emendation of Australisphaera by Harding, 1986 however, see Harding (1990b, p.21).
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Modified description:
Stover and Williams, 1987, p. 31:
Synopsis:
Cysts proximate, autophragm lenticular, with one or two antapical and two lateral lobes or horns, additional lobes or horns may be present, autophragm ornamented with features of low relief, archeopyle apical, probably type (tA); operculum free, offset parasulcal notch poorly developed. Isolated opercula and complete specimens have not been identified.
Description:
Shape: Lenticular, outline subpolygonal; an antapical and two lateral variably developed protrusions usually present; additional protrusions may be present Outline of apex unknown.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Autophragm with features of low relief to spinose.
Archeopyle: Apical, probably type [tA]; operculum free; in-place or free opercula not observed.
Paratabulation: Generally indicated by archeopyle only; other features faint or inconsistently developed.
Paracingulum: Possibly indicated by two lateral projections posterior to archeopyle margins.
Parasulcus: Not indicated; offset parasulcal notch not a conspicuous feature.
Size: Intermediate to large, about 60 µm to 140 µm in width.
Affinities:
Australisphaera differs from Canningia Cookson and Eisenack 1960 emended Below 1981 in having a single rather than two wall layers and forms of Australisphaera, which possess two lateral and two antapical horns, differ from Muderongia Cookson and Eisenack 1958 in being acavate. The latter difference applies also to the dinoflagellates identified as "Muderongia" sp. A of Nichols and Jacobson (1982). Cyclonephelium Deflandre and Cookson 1955 emended Sarjeant and Stover 1978 differs from Australisphaera in having more prominent ornamentation and in lacking lateral lobes; however, Cyclonephelium may have one or two antapical lobes, but not antapical horns.