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Apteodinium
From Fensome et al., 2019:
Apteodinium, Eisenack, 1958a, p.385.
Emendations: Sarjeant, 1985a, p.78; Lucas-Clark, 1987, p.168,170.
Taxonomic junior synonyms: Archeotectatum, Coniferatium, Dodekovia and Emslandia, all according to Stover and Evitt (1978, p.141–142) -- however, Prauss (1989, p.18) retained Dodekovia and Lentin and Williams (1981, p.18; 1989, p.24) retained Archeotectatum.
Riding and Fensome (2002, p.19) considered that Aldorfia may be a junior synonym of Apteodinium.
Type: Eisenack, 1958a, pl.23, fig.9, as Apteodinium granulatum.
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Original diagnosis: [Eisenack, 1958]: (Translation: Norris and Sarjeant, 1965, p. 11 (description), LPP (affinities))
Diagnosis:
Shell globular, oval to ovoid, sometimes rounded diamond shaped, with a short pointed apical horn; without tabulation, without ornamentation (spines, crests). Epi- and hypovalve separated by a narrow, scarcely depressed (and then often visible with difficulty or not visible at all) unspiraled girdle. Longitudinal furrow not present. Pylome frequent, on dorsal side of epivalve below apical horn. Occasionally a small antapical horn occurs.
Affinities:
Apteodinium differs from Pareodinia Deflandre, 1947 in that its species more or less often possess a girdle, as the equivalent of the transverse furrow (always the entire population is to be evaluated), and in the position and shape of the pylome.
Apteodinium differs from Eodinia Eisenack, 1936 in that Eodinia possesses an equatorial ring-seam, where the shells easily split in two parts, which is not the case in Apteodinium. Also, Eodinia possesses a slight indentation on the lower shell, as an equivalent of the longitudinal furrow, which is absent in Apteodinium.
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Modified description:
Stover and Evitt, 1978, p. 141:
Synopsis: Cysts proximate, subspherical, normally with short apical projection; autophragm may bear some nontabular features of low relief; paratabulation indicated typically by archeopyle and paracingulum, occasionally also by faint parasutural features in equatorial area; archeopyle precingular, Type P.
Description:
Shape: Generally subspherical, occasionally somewhat rhomboidal, usually with an apical projection.
Wall relationships: Autophragm only.
Wall features: Parasutural features normally absent, except that faint parasutural markings or low ridges may occur in equatorial area. Autophragm variously ornamented with features of low relief.
Paratabulation: Typically indicated by archeopyle and paracingulum; additional indications, such as faint parasutural markings or low ridges, vague and confined to precingular and postcingular areas.
Archeopyle: Precingular, Type P (3" only); operculum free.
Paracingulum: Vaguely to clearly expressed as a shallow, transverse, equatorial depression; may be bordered by low ridges.
Parasulcus: Not indicated.
Size: Intermediate to large.
Affinities:
Apteodinium differs from Millioudodinium in lacking indications of paratabulation other than the archeopyle and paracingulum. On a few species of Apteodinium faint traces of parasutural features may be seen adjacent to the paracingulum, but such traces are usually indistinct and inconsistent. In Millioudodinium, the paratabulation is normally clearly discernible and expressed more or less completely.
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Emended descriptions:
Sarjeant, 1985:
Diagnosis:
Proximate, cryptotabulate cysts, acavate to monocornucavate, epicavate or bicavate (with antapical cavation feebly developed). Phragma of variable thickness, composed of one or two layers; in the latter condition, the endophragm is considerably thicker than the periphragm. Ambitus spherical to spheroidal, rounded-subpolygonal or broadly ellipsoidal, with an apical mamelon or short horn but without antapical prominences or horns. Processes or other major outgrowths lacking.
Cingulum distinct, marked by an indentation or raised ridges; sulcus feebly marked or not directly indicated; paratabulation otherwise very feebly indicated or not at all.
Archaeopyle single-plate precingular, type P.
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Lucas-Clark, 1987:
Description:
Intermediate to large, acavate, subspherical to slightly rhomboidal cysts, circular in equatorial section, usually with prominent apical horn. Cyst basically an autophragm, but wall structure and ornament variable: wall may be (1) smooth, (2) ornamented with features of low relief, (3) spongy, (4) cavernous, (5) have short processes with connected tips, or (6) have columns and muri supporting an outer layer that is usually discontinuous and/or perforate, and which could be considered to be either periphragm or, ectophragm. Exact structure of wall often difficult to recognize with light microscopy.
Archeopyle precingular, type P(4), operculum usually enlarged along cingular and precingular margins, rounded, free. Paracingulum typically marked by faint ridges and transverse equatorial depression, but not developed into cingular flange. Paratabulation, where indicated, gonyaulacoid and similar to that of Cribroperidinium; usually obscured by ornament and complexities of wall structure, or not indicated. Paratabulation may be faintly expressed in some areas by intratabular ornament, low parasutural ridges, or smooth areas between paraplates, but these features usually visible only with scanning electron microscopy. Growth bands variably expressed by faint accessory ridges.
The following paraplates can be demonstrated in some specimens: one preapical (P), four apicals (1u, B, C, A), six precingulars (1i, 2-6), two sulcals (ai, Z), one posterior intercalary (X), six postcingulars (Iu, II-VI), and one antapical (Y). Ventral organization: elongated A and 1u contact 1i; ends of cingulum offset slightly. Apical organization uncertain. Posterior sulcal organization uncertain, except for involving a more-or-less elongate X. Dorsal organization: IV/V parasuture offset at least slightly to the left of 4/5. Hypocystal organization: sexiform, Y, at least slightly asymmetrical with V/Y parasuture longer than III/Y parasuture. In some species positioned partly on the ventral side of the cyst and typically rotated so that the IV/V/Y triple junction is about mid-dorsal. This triple junction often forms an antapical protrusion.
Affinities:
Apteodinium is similar to Cribroperidinium in paratabulation, and also to many species of that genus in having some accessory ridges related to growth bands. However, it differs from Cribroperidinium in having paratabulation that is faint, only partially expressed, and usually not discernible in light microscopy, whereas Cribroperidinium has parasutural ridges or septa, and shows a complete paratabulation pattern. Some species of Apteodinium, as emended herein, have a thick, complex, spongy wall structure which is in contrast to most species of Cribroperidinium. Apteodinium differs from Spongodinium in lacking a wall distinguished by bubble-like vesicles and in lacking a cingular flange.
It differs from Wigginsiella in lacking spines, a cingular flange, and the distinctive perforate ornamentation.
It differs from Aldorfia in typically having a more rounded shape, in lacking evidence of a Q paraplate and/or K paraplates, and in having more elongate, less blocky-shaped X and Z paraplates.
Apteodinium, Eisenack, 1958a, p.385.
Emendations: Sarjeant, 1985a, p.78; Lucas-Clark, 1987, p.168,170.
Taxonomic junior synonyms: Archeotectatum, Coniferatium, Dodekovia and Emslandia, all according to Stover and Evitt (1978, p.141–142) -- however, Prauss (1989, p.18) retained Dodekovia and Lentin and Williams (1981, p.18; 1989, p.24) retained Archeotectatum.
Riding and Fensome (2002, p.19) considered that Aldorfia may be a junior synonym of Apteodinium.
Type: Eisenack, 1958a, pl.23, fig.9, as Apteodinium granulatum.
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Original diagnosis: [Eisenack, 1958]: (Translation: Norris and Sarjeant, 1965, p. 11 (description), LPP (affinities))
Diagnosis:
Shell globular, oval to ovoid, sometimes rounded diamond shaped, with a short pointed apical horn; without tabulation, without ornamentation (spines, crests). Epi- and hypovalve separated by a narrow, scarcely depressed (and then often visible with difficulty or not visible at all) unspiraled girdle. Longitudinal furrow not present. Pylome frequent, on dorsal side of epivalve below apical horn. Occasionally a small antapical horn occurs.
Affinities:
Apteodinium differs from Pareodinia Deflandre, 1947 in that its species more or less often possess a girdle, as the equivalent of the transverse furrow (always the entire population is to be evaluated), and in the position and shape of the pylome.
Apteodinium differs from Eodinia Eisenack, 1936 in that Eodinia possesses an equatorial ring-seam, where the shells easily split in two parts, which is not the case in Apteodinium. Also, Eodinia possesses a slight indentation on the lower shell, as an equivalent of the longitudinal furrow, which is absent in Apteodinium.
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Modified description:
Stover and Evitt, 1978, p. 141:
Synopsis: Cysts proximate, subspherical, normally with short apical projection; autophragm may bear some nontabular features of low relief; paratabulation indicated typically by archeopyle and paracingulum, occasionally also by faint parasutural features in equatorial area; archeopyle precingular, Type P.
Description:
Shape: Generally subspherical, occasionally somewhat rhomboidal, usually with an apical projection.
Wall relationships: Autophragm only.
Wall features: Parasutural features normally absent, except that faint parasutural markings or low ridges may occur in equatorial area. Autophragm variously ornamented with features of low relief.
Paratabulation: Typically indicated by archeopyle and paracingulum; additional indications, such as faint parasutural markings or low ridges, vague and confined to precingular and postcingular areas.
Archeopyle: Precingular, Type P (3" only); operculum free.
Paracingulum: Vaguely to clearly expressed as a shallow, transverse, equatorial depression; may be bordered by low ridges.
Parasulcus: Not indicated.
Size: Intermediate to large.
Affinities:
Apteodinium differs from Millioudodinium in lacking indications of paratabulation other than the archeopyle and paracingulum. On a few species of Apteodinium faint traces of parasutural features may be seen adjacent to the paracingulum, but such traces are usually indistinct and inconsistent. In Millioudodinium, the paratabulation is normally clearly discernible and expressed more or less completely.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended descriptions:
Sarjeant, 1985:
Diagnosis:
Proximate, cryptotabulate cysts, acavate to monocornucavate, epicavate or bicavate (with antapical cavation feebly developed). Phragma of variable thickness, composed of one or two layers; in the latter condition, the endophragm is considerably thicker than the periphragm. Ambitus spherical to spheroidal, rounded-subpolygonal or broadly ellipsoidal, with an apical mamelon or short horn but without antapical prominences or horns. Processes or other major outgrowths lacking.
Cingulum distinct, marked by an indentation or raised ridges; sulcus feebly marked or not directly indicated; paratabulation otherwise very feebly indicated or not at all.
Archaeopyle single-plate precingular, type P.
--------------------------------------------
Lucas-Clark, 1987:
Description:
Intermediate to large, acavate, subspherical to slightly rhomboidal cysts, circular in equatorial section, usually with prominent apical horn. Cyst basically an autophragm, but wall structure and ornament variable: wall may be (1) smooth, (2) ornamented with features of low relief, (3) spongy, (4) cavernous, (5) have short processes with connected tips, or (6) have columns and muri supporting an outer layer that is usually discontinuous and/or perforate, and which could be considered to be either periphragm or, ectophragm. Exact structure of wall often difficult to recognize with light microscopy.
Archeopyle precingular, type P(4), operculum usually enlarged along cingular and precingular margins, rounded, free. Paracingulum typically marked by faint ridges and transverse equatorial depression, but not developed into cingular flange. Paratabulation, where indicated, gonyaulacoid and similar to that of Cribroperidinium; usually obscured by ornament and complexities of wall structure, or not indicated. Paratabulation may be faintly expressed in some areas by intratabular ornament, low parasutural ridges, or smooth areas between paraplates, but these features usually visible only with scanning electron microscopy. Growth bands variably expressed by faint accessory ridges.
The following paraplates can be demonstrated in some specimens: one preapical (P), four apicals (1u, B, C, A), six precingulars (1i, 2-6), two sulcals (ai, Z), one posterior intercalary (X), six postcingulars (Iu, II-VI), and one antapical (Y). Ventral organization: elongated A and 1u contact 1i; ends of cingulum offset slightly. Apical organization uncertain. Posterior sulcal organization uncertain, except for involving a more-or-less elongate X. Dorsal organization: IV/V parasuture offset at least slightly to the left of 4/5. Hypocystal organization: sexiform, Y, at least slightly asymmetrical with V/Y parasuture longer than III/Y parasuture. In some species positioned partly on the ventral side of the cyst and typically rotated so that the IV/V/Y triple junction is about mid-dorsal. This triple junction often forms an antapical protrusion.
Affinities:
Apteodinium is similar to Cribroperidinium in paratabulation, and also to many species of that genus in having some accessory ridges related to growth bands. However, it differs from Cribroperidinium in having paratabulation that is faint, only partially expressed, and usually not discernible in light microscopy, whereas Cribroperidinium has parasutural ridges or septa, and shows a complete paratabulation pattern. Some species of Apteodinium, as emended herein, have a thick, complex, spongy wall structure which is in contrast to most species of Cribroperidinium. Apteodinium differs from Spongodinium in lacking a wall distinguished by bubble-like vesicles and in lacking a cingular flange.
It differs from Wigginsiella in lacking spines, a cingular flange, and the distinctive perforate ornamentation.
It differs from Aldorfia in typically having a more rounded shape, in lacking evidence of a Q paraplate and/or K paraplates, and in having more elongate, less blocky-shaped X and Z paraplates.