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Ascodinium
From Williams et al., 2017:
[Ascodinium, Cookson and Eisenack, 1960a, p. 5; Emendations: Helenes, 1983, p. 258-260
Tax. jr. syn.: Pocockia and Ovoidinium, both according to Helenes (1983, p.258), and by implication Evittia Pocock (an illegitimate name for which Pocockia is the substitute) — however, Lentin and Williams (1989, p.269) retained Ovoidinium (including by implication Pocockia and Evittia).
Type species: Ascodinium acrophorum, Cookson and Eisenack, 1960a (pl.1, fig.19)]
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Original description: [Cookson and Eisenack, 1960]:
Description:
Shell rather flat, oval to rhomboidal in outline with or without apical and antapical horns and girdle, and containing an ovoidal, spheroidal, or rhomboidal capsule. Pylome formed on the dorsal surface by the detachment of a circular part of the apical region, including the apex itself, and part of the central wall.
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Modified description:
Stover and Evitt, 1978, p. 200-201:
Synopsis:
Cysts proximate, circumcavate, lenticular to compressed biconical, with or without apical protrusion or horn; paratabulation absent or involves archeopyle only; archeopyle Type tAtl, its outline commonly rounded.
Description:
Shape: Lenticular to compressed biconical, with or without a short apical protrusion or horn; short antapical protrusion or horn usually present.
Wall relationships: Cysts circumcavate.
Wall features: No parasutural features. Periphragm and endophragm usually smooth or have features of low relief, which are commonly confined to relatively small areas.
Archeopyle: Combination, Type tAtl, without accessory archeopyle sutures; constituent paraplate boundaries not indicated, and angles and reentrants along archeopyle margin are rounded.
Paratabulation: Indicated by archeopyle only, which is commonly rounded; when well-developed its outline indicates Type tAtl. Perioperculum tends to remain attached ventrally; endoperculum free.
Paracingulum: Indicated faintly, or not at all.
Parasulcus: Not indicated.
Size: Small to intermediate.
Affinities:
Ascodinium differs from Ovoidinium in being circumcavate instead of bicavate. Ascodinium and Subtilisphaera are similar in shape except that Subtilisphaera lacks an archeopyle and usually has a discernible paracingulum.
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Emended description:
Helenes, 1983:
Diagnosis:
Proximate cysts, with or without apical or antapical horns. Thin periphragm around thicker, subspherical to ovoidal endocyst. Contact between layers variable, so that cyst may be bicavate or circumcavate or present an irregularly and discontinuously distributed pericoel. Paratabulation, when expressed, is peridinioid, represented by the archeopyle and faint paracingluar features and more or less incompletely by traces of parasutures. Formula 4`, 3a, 7", Xc, 5"`, 2"", Xs. Archeopyle type (tAtl), its outline angular to rounded.
Remarks:
The periphragm may be missing in poorly preserved specimens; it is usually smooth or finely spinose or granulose. The apical and antapical horns, which are formed by the periphragm and define a peridinioid outline, may be well developed or not. The endophragm, which may be smooth or ornamented with features of low relief, is usually circular to elliptical in outline. Features indicating paratabulation are the archeopyle outline and typically faint or incomplete parasutural features on the hypoperiphragm and endophragm. A complete paratabulation pattern has been observed in only one species (A. diversum, as described here), in which it is ortho-hexa peridinioid (text- fig. 2). The operculum is commonly free, although often adherent, and it may be adnate.
Species in this genus may be distinguished by: 1 ) variations in the wall relationships; 2) distribution of pericoels; 3) degree of angularity of archeopyle; 4) size of the archeopyle in relation to the entire cyst; and 5) definition and obvious variations in surface ornamentation.
Affinities:
The following genera are in some respects similar to Ascodinium, but they differ from it as noted:
Brigantedinium Reid 1977 has an autophragm and an intercalary archeopyle.
Chytroeisphaeridia (Sarjeant 1962) Davey 1979 has a precingluar archeopyle.
Fromea Cookson and Eisenack 1958 has an autophragm and a completely rounded archeopyle at the apex.
Hexagonifera Cookson and Eisenack 1961 has an autophragm and an intercalary archeopyle.
Leberidocysta Stover and Evitt 1978 has a type (tA) archeopyle. If Craspedodinium has the same type of archeopyle, Leberidocysta may be a junior synonym.
Maturodinium Morgenroth 1970 has a gonyaulacoid paratabulation .
Subtilisphaera Jain and Millepied 1973 typically lacks an archeopyle.
Xenikoon Cookson and Eisenack 1960 has an intercalary (type 1) archeopyle.
Yalkalpodinium Morgan 1980 has a type (tA) archeopyle and a gonyaulacoid paratabulation. It may also be a junior synonym of Craspedodinium.
[Ascodinium, Cookson and Eisenack, 1960a, p. 5; Emendations: Helenes, 1983, p. 258-260
Tax. jr. syn.: Pocockia and Ovoidinium, both according to Helenes (1983, p.258), and by implication Evittia Pocock (an illegitimate name for which Pocockia is the substitute) — however, Lentin and Williams (1989, p.269) retained Ovoidinium (including by implication Pocockia and Evittia).
Type species: Ascodinium acrophorum, Cookson and Eisenack, 1960a (pl.1, fig.19)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Cookson and Eisenack, 1960]:
Description:
Shell rather flat, oval to rhomboidal in outline with or without apical and antapical horns and girdle, and containing an ovoidal, spheroidal, or rhomboidal capsule. Pylome formed on the dorsal surface by the detachment of a circular part of the apical region, including the apex itself, and part of the central wall.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Evitt, 1978, p. 200-201:
Synopsis:
Cysts proximate, circumcavate, lenticular to compressed biconical, with or without apical protrusion or horn; paratabulation absent or involves archeopyle only; archeopyle Type tAtl, its outline commonly rounded.
Description:
Shape: Lenticular to compressed biconical, with or without a short apical protrusion or horn; short antapical protrusion or horn usually present.
Wall relationships: Cysts circumcavate.
Wall features: No parasutural features. Periphragm and endophragm usually smooth or have features of low relief, which are commonly confined to relatively small areas.
Archeopyle: Combination, Type tAtl, without accessory archeopyle sutures; constituent paraplate boundaries not indicated, and angles and reentrants along archeopyle margin are rounded.
Paratabulation: Indicated by archeopyle only, which is commonly rounded; when well-developed its outline indicates Type tAtl. Perioperculum tends to remain attached ventrally; endoperculum free.
Paracingulum: Indicated faintly, or not at all.
Parasulcus: Not indicated.
Size: Small to intermediate.
Affinities:
Ascodinium differs from Ovoidinium in being circumcavate instead of bicavate. Ascodinium and Subtilisphaera are similar in shape except that Subtilisphaera lacks an archeopyle and usually has a discernible paracingulum.
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Emended description:
Helenes, 1983:
Diagnosis:
Proximate cysts, with or without apical or antapical horns. Thin periphragm around thicker, subspherical to ovoidal endocyst. Contact between layers variable, so that cyst may be bicavate or circumcavate or present an irregularly and discontinuously distributed pericoel. Paratabulation, when expressed, is peridinioid, represented by the archeopyle and faint paracingluar features and more or less incompletely by traces of parasutures. Formula 4`, 3a, 7", Xc, 5"`, 2"", Xs. Archeopyle type (tAtl), its outline angular to rounded.
Remarks:
The periphragm may be missing in poorly preserved specimens; it is usually smooth or finely spinose or granulose. The apical and antapical horns, which are formed by the periphragm and define a peridinioid outline, may be well developed or not. The endophragm, which may be smooth or ornamented with features of low relief, is usually circular to elliptical in outline. Features indicating paratabulation are the archeopyle outline and typically faint or incomplete parasutural features on the hypoperiphragm and endophragm. A complete paratabulation pattern has been observed in only one species (A. diversum, as described here), in which it is ortho-hexa peridinioid (text- fig. 2). The operculum is commonly free, although often adherent, and it may be adnate.
Species in this genus may be distinguished by: 1 ) variations in the wall relationships; 2) distribution of pericoels; 3) degree of angularity of archeopyle; 4) size of the archeopyle in relation to the entire cyst; and 5) definition and obvious variations in surface ornamentation.
Affinities:
The following genera are in some respects similar to Ascodinium, but they differ from it as noted:
Brigantedinium Reid 1977 has an autophragm and an intercalary archeopyle.
Chytroeisphaeridia (Sarjeant 1962) Davey 1979 has a precingluar archeopyle.
Fromea Cookson and Eisenack 1958 has an autophragm and a completely rounded archeopyle at the apex.
Hexagonifera Cookson and Eisenack 1961 has an autophragm and an intercalary archeopyle.
Leberidocysta Stover and Evitt 1978 has a type (tA) archeopyle. If Craspedodinium has the same type of archeopyle, Leberidocysta may be a junior synonym.
Maturodinium Morgenroth 1970 has a gonyaulacoid paratabulation .
Subtilisphaera Jain and Millepied 1973 typically lacks an archeopyle.
Xenikoon Cookson and Eisenack 1960 has an intercalary (type 1) archeopyle.
Yalkalpodinium Morgan 1980 has a type (tA) archeopyle and a gonyaulacoid paratabulation. It may also be a junior synonym of Craspedodinium.