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Aptea
From Fensome et al., 2019:
Aptea, Eisenack, 1958a, p.393.
Emendations: Davey and Verdier, 1974, p.640–641; Dörhöfer and Davies, 1980, p.33; Fensome et al. 2019a, p.11.
Taxonomic senior synonym: Pseudoceratium, according to Bint (1986, p.144) -- however, Quattrocchio and Sarjeant (1992, p.2–234) retained Aptea.
Taxonomic junior synonyms: Doidyx, according to Sarjeant and Stover (1978, p.51); however, Fensome et al., 2019a, p.45 considered Doidyx to be a taxonomic junior synonym of Tenua Eisenack; Cassidium, according to Fensome et al. (2019a, p.11).
Type: Eisenack, 1958a, pl.22, fig.5, as Aptea polymorpha.
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Original description: [Eisenack, 1958]: (Translation: Stover and Evitt, 1978, p. 393)
Diagnosis:
Shell in transverse section flat-oval, in outline irregularly triangular with swollen sides and 3 (also 4?) poorly marked horns, which may be extensively reduced, so that the outline is very variable and tends to assume an oval to circular shape.
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Emended descriptions:
Davey and Verdier, 1974:
Description:
Dorso-ventrally flattened cyst with typically a rounded triangular outline and possessing an ornamentation of membranous crests and/or processes which is better developed in the circumferential region. The apices of the triangle are situated at the apex, antapex, and a little antapically to the right cingular margin of the cyst; they are typically marked by distinctively high ornamentation, and the cyst wall may or may not have prominent rounded protuberances in these positions. A detached inner body, elongate horns, and flat or indent (two horns) antapical region are never present. The crests and processes are intertabular and rarely show alignment parallel to to plate boundaries. The archeopyle is apical with strongly zigzag margin and short breakages extending along the precingular plate boundaries. The sulcal notch is always offset from the mid-line of the cyst`s ventral surface, Finally, the operculum often remains attached.
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Dörhöfer and Davies, 1980
Affinities:
Some species of Aptea are considered to be transitional to cavate types, as the ornament is developed on an otherwise smooth autophragm; but the terminal ends of the processes tend to fuse. Total fusion would result in the formation of cavate forms like Endoceratium. Transitional forms between Aptea and Endoceratium do exist. The type species E. ludbrookiae (Cookson and Eisenack) Vozzhennikova 1965 exhibits broad supporting ridges between the endophragm and periphragm (Norvick and Burger 1976). As already partially expressed by Davey and Verdier (1974) the following criteria are particularly important in differentiating Aptea from similar genera: asymmetry of the cyst body, considerable reduction of horns, always ornamented, (4A2I) type archaeopyle. Cyclonephelium Deflandre and Cookson 1955 and Batiacasphaera Drugg emend. are typically asymmetrical and most probably have an (4A) archaeopyle. Muderongia Cookson and Eisenack 1958 and Phoberocysta Millioud 1969 have two postcingular horns. Odontochitina Deflandre 1936 contains only smooth forms. Aptea is morphologically similar to Heterosphaeridium and Pseudoceratium, occupying an intermediate position between them. The processes become increasingly closer, longer, and more slender proceeding from Pseudoceratium to Hetrosphaeridium.
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Modified description:
Stover and Evitt, 1978, p. 16-17:
Synopsis:
Cysts proximate, compressed ceratioid to lenticular with an apical, an antapical, and a third, probably postcingular, horn; the last two may be reduced extensively; ornamentation forms an incomplete network and is commonly least developed on the midventral and middorsal surfaces; archeopyle apical, Type tA; parasutural notch offset.
Description:
Shape: Compressed ceratioid to lenticular, with an apical, an antapical, and a third, probably postcingular, horn. The horns, especially those on the hypocyst, may be reduced extensively so that the cyst outline in dorsal-ventral view is subcircular.
Wall relationships: Generally autophragm only, occasionally with an incompletely developed ectophragm.
Wall features: Parasutural features generally absent. Autophragm ornamented with short, generally curved ridges or bifurcate, often
coalescing processes that may be partially covered distally by a faint ectophragm; the ornamentation, which may give the impression of a irregular and incomplete network, commonly least developed on the midventral and middorsal surfaces.
Paratabulation: Indicated by archeopyle only; formula unknown, probably ceratiacean.
Archeopyle: Apical, Type tA; principal archeopyle suture zigzag; parasulcal notch offset; operculum free. Paracingulum: Generally not indicated.
Parasulcus: Not indicated.
Size: Intermediate to large.
Affinities:
Aptea differs from Endoceratium in having an autophragm that occasionally may be partially covered by an ectophragm, and in lacking indications of paratabulation other than the archeopyle.
Endoceratium is cavate and its paratabulation is expressed by low parasutural ridges as well as by the archeopyle.
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From Fensome et al., 2019a
Areoligeracean cysts that are proximate to proximochorate, with ornament height less than 25% of maximum cyst width. Central body dorsoventrally compressed, ambitus subcircular to lenticular, with a rounded to more commonly asymmetrical antapex and an apical horn; lateral horns or prominences formed by the central body are absent, although a lateral prominence may be formed by ornament. Acavate. Ornamentation consisting of linear elements such as crests or ridges, or free-standing elements that are in large part fused or connected to adjacent elements; ornament is more or less uniformly distributed over the cyst. Archaeopyle apical, with formula A(1–4′), operculum free; parasulcal notch offset to the left.
Comments. [...] Aptea is here considered an areoligeracean genus and not, as determined by some authors, a taxonomic junior synonym of Pseudoceratium. It is distinguished by ornament that is entirely or for the most part composed of linear elements, and this ornament is not absent dorsoventrally, although it may be reduced. Cyclonephelium also has predominantly linear sculptural elements but has dorsoventral areas devoid of ornament.
Aptea, Eisenack, 1958a, p.393.
Emendations: Davey and Verdier, 1974, p.640–641; Dörhöfer and Davies, 1980, p.33; Fensome et al. 2019a, p.11.
Taxonomic senior synonym: Pseudoceratium, according to Bint (1986, p.144) -- however, Quattrocchio and Sarjeant (1992, p.2–234) retained Aptea.
Taxonomic junior synonyms: Doidyx, according to Sarjeant and Stover (1978, p.51); however, Fensome et al., 2019a, p.45 considered Doidyx to be a taxonomic junior synonym of Tenua Eisenack; Cassidium, according to Fensome et al. (2019a, p.11).
Type: Eisenack, 1958a, pl.22, fig.5, as Aptea polymorpha.
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Original description: [Eisenack, 1958]: (Translation: Stover and Evitt, 1978, p. 393)
Diagnosis:
Shell in transverse section flat-oval, in outline irregularly triangular with swollen sides and 3 (also 4?) poorly marked horns, which may be extensively reduced, so that the outline is very variable and tends to assume an oval to circular shape.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended descriptions:
Davey and Verdier, 1974:
Description:
Dorso-ventrally flattened cyst with typically a rounded triangular outline and possessing an ornamentation of membranous crests and/or processes which is better developed in the circumferential region. The apices of the triangle are situated at the apex, antapex, and a little antapically to the right cingular margin of the cyst; they are typically marked by distinctively high ornamentation, and the cyst wall may or may not have prominent rounded protuberances in these positions. A detached inner body, elongate horns, and flat or indent (two horns) antapical region are never present. The crests and processes are intertabular and rarely show alignment parallel to to plate boundaries. The archeopyle is apical with strongly zigzag margin and short breakages extending along the precingular plate boundaries. The sulcal notch is always offset from the mid-line of the cyst`s ventral surface, Finally, the operculum often remains attached.
--------------------------------------------
Dörhöfer and Davies, 1980
Affinities:
Some species of Aptea are considered to be transitional to cavate types, as the ornament is developed on an otherwise smooth autophragm; but the terminal ends of the processes tend to fuse. Total fusion would result in the formation of cavate forms like Endoceratium. Transitional forms between Aptea and Endoceratium do exist. The type species E. ludbrookiae (Cookson and Eisenack) Vozzhennikova 1965 exhibits broad supporting ridges between the endophragm and periphragm (Norvick and Burger 1976). As already partially expressed by Davey and Verdier (1974) the following criteria are particularly important in differentiating Aptea from similar genera: asymmetry of the cyst body, considerable reduction of horns, always ornamented, (4A2I) type archaeopyle. Cyclonephelium Deflandre and Cookson 1955 and Batiacasphaera Drugg emend. are typically asymmetrical and most probably have an (4A) archaeopyle. Muderongia Cookson and Eisenack 1958 and Phoberocysta Millioud 1969 have two postcingular horns. Odontochitina Deflandre 1936 contains only smooth forms. Aptea is morphologically similar to Heterosphaeridium and Pseudoceratium, occupying an intermediate position between them. The processes become increasingly closer, longer, and more slender proceeding from Pseudoceratium to Hetrosphaeridium.
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Modified description:
Stover and Evitt, 1978, p. 16-17:
Synopsis:
Cysts proximate, compressed ceratioid to lenticular with an apical, an antapical, and a third, probably postcingular, horn; the last two may be reduced extensively; ornamentation forms an incomplete network and is commonly least developed on the midventral and middorsal surfaces; archeopyle apical, Type tA; parasutural notch offset.
Description:
Shape: Compressed ceratioid to lenticular, with an apical, an antapical, and a third, probably postcingular, horn. The horns, especially those on the hypocyst, may be reduced extensively so that the cyst outline in dorsal-ventral view is subcircular.
Wall relationships: Generally autophragm only, occasionally with an incompletely developed ectophragm.
Wall features: Parasutural features generally absent. Autophragm ornamented with short, generally curved ridges or bifurcate, often
coalescing processes that may be partially covered distally by a faint ectophragm; the ornamentation, which may give the impression of a irregular and incomplete network, commonly least developed on the midventral and middorsal surfaces.
Paratabulation: Indicated by archeopyle only; formula unknown, probably ceratiacean.
Archeopyle: Apical, Type tA; principal archeopyle suture zigzag; parasulcal notch offset; operculum free. Paracingulum: Generally not indicated.
Parasulcus: Not indicated.
Size: Intermediate to large.
Affinities:
Aptea differs from Endoceratium in having an autophragm that occasionally may be partially covered by an ectophragm, and in lacking indications of paratabulation other than the archeopyle.
Endoceratium is cavate and its paratabulation is expressed by low parasutural ridges as well as by the archeopyle.
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From Fensome et al., 2019a
Areoligeracean cysts that are proximate to proximochorate, with ornament height less than 25% of maximum cyst width. Central body dorsoventrally compressed, ambitus subcircular to lenticular, with a rounded to more commonly asymmetrical antapex and an apical horn; lateral horns or prominences formed by the central body are absent, although a lateral prominence may be formed by ornament. Acavate. Ornamentation consisting of linear elements such as crests or ridges, or free-standing elements that are in large part fused or connected to adjacent elements; ornament is more or less uniformly distributed over the cyst. Archaeopyle apical, with formula A(1–4′), operculum free; parasulcal notch offset to the left.
Comments. [...] Aptea is here considered an areoligeracean genus and not, as determined by some authors, a taxonomic junior synonym of Pseudoceratium. It is distinguished by ornament that is entirely or for the most part composed of linear elements, and this ornament is not absent dorsoventrally, although it may be reduced. Cyclonephelium also has predominantly linear sculptural elements but has dorsoventral areas devoid of ornament.