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Apiculadinium
From Williams et al., 2017:
[Apiculadinium, Yu Jing-xian et al., 1981, p. 261-262; Emendation: Chen et al., 1988, p.3-4
Chen et al. (1988, p.6) considered Bellatudinium to be a possible taxonomic synonym of this genus.
Type species: Apiculadinium ovatum, Yu Jing-xian et al., 1981 (pl.1, fig.36)]
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Original description: [Yu Jing-xian, 1981]: (Translation : Chen et al., 1988, p. 4; Provisional translation GSC: courtesy R. Fensome)
Description:
Cysts proximate, roundly conical to pear-shaped or ovoidal. Epicyst outline triangular with an apical horn; hypocyst more or less hemispherical, smaller than epicyst, without antapical horns, but a short baculate spine may occur at the antapex. Wall thin, endophragm and periphragm separated only at the apex and antapex, appressed elsewhere. Surface granulate and ornamented with numerous, irregular folds. Paratabulation indicated by paracingulum only, which is prominent, planar or slightly helicoidal. Archeopyle not discernible.
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Emended description:
Chen et al., 1988
Synopsis:
Cysts proximate, outline ovate to roughly triangular; epicyst longer than hypocyst; endiphragm and periphragm separated apically and antapically, appressed elsewhere; surface ornamented with features of low relief, and also with fine folds; paratabulaton indicated by paracingulum only; archaeopyle not discernible.
Description:
Shape: Roundly conical to pear-shaped or ovoidal; epicyst conical, outline more or less triangular, longer than hypocyst; latter hemispherical. Apical horn may be present, antapical horns lacking.
Wall relationships: Endophragm and periphragm separated slightly apically and antapically, appressed elsewhere.
Wall features: Surface granulate and finely folded.
Archeopyle: Not discernible.
Paratabulation: Expressed by paracingulum only.
Paracingulum: Expressed by transverse folds.
Parasulcus: Not indicated.
Size: Small to intermediate, about 40 µm to 60 µm in length
Affinities:
According to Yu Jingxian et al. (1981, p. 261), Apiculadinium differs from Laciniadinium McIntyre 1975 in having an indiscernible rather than a combined intercalary and precingular archeopyle, and from Hebecysta Bujak and Fisher 1976 in not having an intercalary archeopyle. Perhaps a somewhat closer comparison can be made, for example, between Apiculadinium and Geiselodinium Krutzsch 1962 or Subtilisphaera Jain and Millepied 1973, which either lack an archeopyle, or have an inconsistently developed archeopyle. In general, the epipericoels and hypopericoels on Geiselodinium and Subtilisphaera are more prominent than those on Apiculadinium.
The recognition of Apiculadinium and Bellatudinium as separate genera is based on the generic descriptions, not on the illustrations. In our opinion, the illustrated specimens of Apiculadinium and Bellatudinium are virtually indistinguishable and those of the former are not clearly cavate. If our interpretation is correct, the two genera are synonymous.
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GSC:
Proximate cysts. Outline conical, pyriform to oval. Periphragm only, thin. Endocyst closely appressed to periphragm. Periphragm and endophragm show at antapex. Surface granulate and with many irregular creases. Sometimes antapical region has short rhabdoidal spines. Upper test triangular. Apical horn is extension of upper test and does not project beyond contour line. Lower test smaller than a semicircle. Antapical horns generally undeveloped. Cingulum conspicuous, annular or slightly spiraled. Tabulation unclear. No archeopyle observed.
Discussion:
With its proximate cysts, conspicuous presence of periphragm and endophragm solely at the apical horn, annular cingulum and general lack of antapical horns, this new genus resembles Laciniadinium but is distinguished from it by the latter`s combination archeopyle and inconspicuous sulcus, if one is present at all. Hebecysta resembles the new genus in its oval to subcircular cysts, small apical horns, undeveloped antapical horns, closely appressed periphragm and endophragm that are conspicuous as two layers only at the apical horn and coronal ridge of the cingulum, and annular cingulum but is distinguished from it by having an intercalary archeopyle and not displaying any sulcus.
[Apiculadinium, Yu Jing-xian et al., 1981, p. 261-262; Emendation: Chen et al., 1988, p.3-4
Chen et al. (1988, p.6) considered Bellatudinium to be a possible taxonomic synonym of this genus.
Type species: Apiculadinium ovatum, Yu Jing-xian et al., 1981 (pl.1, fig.36)]
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Original description: [Yu Jing-xian, 1981]: (Translation : Chen et al., 1988, p. 4; Provisional translation GSC: courtesy R. Fensome)
Description:
Cysts proximate, roundly conical to pear-shaped or ovoidal. Epicyst outline triangular with an apical horn; hypocyst more or less hemispherical, smaller than epicyst, without antapical horns, but a short baculate spine may occur at the antapex. Wall thin, endophragm and periphragm separated only at the apex and antapex, appressed elsewhere. Surface granulate and ornamented with numerous, irregular folds. Paratabulation indicated by paracingulum only, which is prominent, planar or slightly helicoidal. Archeopyle not discernible.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Chen et al., 1988
Synopsis:
Cysts proximate, outline ovate to roughly triangular; epicyst longer than hypocyst; endiphragm and periphragm separated apically and antapically, appressed elsewhere; surface ornamented with features of low relief, and also with fine folds; paratabulaton indicated by paracingulum only; archaeopyle not discernible.
Description:
Shape: Roundly conical to pear-shaped or ovoidal; epicyst conical, outline more or less triangular, longer than hypocyst; latter hemispherical. Apical horn may be present, antapical horns lacking.
Wall relationships: Endophragm and periphragm separated slightly apically and antapically, appressed elsewhere.
Wall features: Surface granulate and finely folded.
Archeopyle: Not discernible.
Paratabulation: Expressed by paracingulum only.
Paracingulum: Expressed by transverse folds.
Parasulcus: Not indicated.
Size: Small to intermediate, about 40 µm to 60 µm in length
Affinities:
According to Yu Jingxian et al. (1981, p. 261), Apiculadinium differs from Laciniadinium McIntyre 1975 in having an indiscernible rather than a combined intercalary and precingular archeopyle, and from Hebecysta Bujak and Fisher 1976 in not having an intercalary archeopyle. Perhaps a somewhat closer comparison can be made, for example, between Apiculadinium and Geiselodinium Krutzsch 1962 or Subtilisphaera Jain and Millepied 1973, which either lack an archeopyle, or have an inconsistently developed archeopyle. In general, the epipericoels and hypopericoels on Geiselodinium and Subtilisphaera are more prominent than those on Apiculadinium.
The recognition of Apiculadinium and Bellatudinium as separate genera is based on the generic descriptions, not on the illustrations. In our opinion, the illustrated specimens of Apiculadinium and Bellatudinium are virtually indistinguishable and those of the former are not clearly cavate. If our interpretation is correct, the two genera are synonymous.
-------------------------------------
GSC:
Proximate cysts. Outline conical, pyriform to oval. Periphragm only, thin. Endocyst closely appressed to periphragm. Periphragm and endophragm show at antapex. Surface granulate and with many irregular creases. Sometimes antapical region has short rhabdoidal spines. Upper test triangular. Apical horn is extension of upper test and does not project beyond contour line. Lower test smaller than a semicircle. Antapical horns generally undeveloped. Cingulum conspicuous, annular or slightly spiraled. Tabulation unclear. No archeopyle observed.
Discussion:
With its proximate cysts, conspicuous presence of periphragm and endophragm solely at the apical horn, annular cingulum and general lack of antapical horns, this new genus resembles Laciniadinium but is distinguished from it by the latter`s combination archeopyle and inconspicuous sulcus, if one is present at all. Hebecysta resembles the new genus in its oval to subcircular cysts, small apical horns, undeveloped antapical horns, closely appressed periphragm and endophragm that are conspicuous as two layers only at the apical horn and coronal ridge of the cingulum, and annular cingulum but is distinguished from it by having an intercalary archeopyle and not displaying any sulcus.