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Atopodinium prostatum
Atopodinium prostratum Drugg, 1978; Emendation: Masure, 1991
Holotype: Drugg, 1978, pl.1, fig.1; Masure, 1991, pl.3, figs.1-2; Fensome et al., 1995, fig.1 - p.1701; Fauconnier and Masure, 2004, pl.10, fig.12.
Isotypes: Drugg, 1978
Locus typicus: Reutlingen, Germany
Stratum typicum: Callovian-Early Oxfordian
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Original description: [Drugg 1978, p.63]:
Description:
Cyst five-sided in basic outline and usually bearing from two to five protruding sack-like lobes at the antapex. The position of these lobes is related to the juncture-points of the hypocystal parasutures. Sometimes one or two additional lobes are present higher on the sides of the hypocyst. The archaeopyle is apical and the operculum is six-sided. Five of the sides are of more or less equal length and the sixth side is relatively narrow and fits into the parasulcal notch. The operculum is sometimes attached at the parasulcal notch but is basically of the free type. The paracinigulum and parasulcus are clearly expressed with the former usually delineated by parallel low ridges or folds. Paratabulation is usually indistinct and is marked by folds and by rows of grana and gemmae. Splits often extend downward from the archaeopyle which help to mark the epicystal paratabulation. The antapical paraplate is usually deeply invaginated into the body interior and is positioned within the antapical lobes. The cyst wall, or autophragm, is thin and varies from smooth to faintly granulate. The paracingulum is slightly laevoratory and is about 5 µm wide. The cyst length ranges from about 65 to 85 µm and the width from 55 to 65 µm.
Affinities:
This genus and species is similar in a number of respects to Stephanelytron Sarjeant 1961. The paratabulation seems to be the same except that a posterior intercalary paraplate has not been seen. The lower part of the parasulcus is broad enough, however, to suggest that it may be present even if not confirmed to date. The evaginated antapical lobes and the invaginated antapical paraplate are very likely homologous to the antapical corona of Stephanelytron.
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Emended description:
Masure, 1991, p.72, 74, 76:
Diagnosis:
Subsphaeroidal, acavate, proximate dinoflagellate cyst with polygonal outline. Thin wall composed of an autophragm, or an endophragm and periphragm in close contact and with a smooth to faintly granulate surface. Sexiform gonyaulacoid inferred thecal tabulation. Paratabulation incompletely delineated and expressed by folds and penitabular rows of grana or gemmae. Large undifferentiated ventral area. The antapical paraplate is usually deeply invaginated into the body interior. Apical archeopyle, type (tA)a, with accessory precingular parasutures. Simple, polyplacoid operculum adnate with the sulcal ai and precingular 2 and 1i paraplates.
Description:
Slightly dorsoventrally compressed, subspheroidal, acavate, proximate dinocyst with inferred sexiform gonyaulacoid thecal tabulation. Paratabulation is incompletely delineated by folds and penitabular rows of grana and/or gemmae. These elements of relief suggest that the paratabulation is composed of ?0-2 preapical(s) (P,Q), 1 anterior intercalary (K), 4 apicals (1u,B,C,A), 6 precingulars (2-6), X cingulars, 5-?6 postcingulars (?Iu,II-VI), ? 1 posterior intercalary (X), 1 antapical (Y), and X sulcals. The apical ornamentation is weakly expressed. Penitabular adcingular rows of grana or gemmae mark the edges of the precingular paraplates. Two rows of grana or gemmae on folds mark the descending paracingulum. The ventral area is untabulated. The sulcal paraplates and the parasutures between the sulcus and the precingular (2, 1i), postcingular (Iu, II, VI) and posterior intercalary (X) paraplates are not expressed by surface features. Only four postcingular parasutures (II/III, III/IV, IV/V, V/VI) are expressed by penitabular ornament of adjacent paraplates in close contact with one another. The postcingular paraplates III, IV, V are of equal size, IV is below precingular 4 and the postcingular parasuture IV/V is aligned with the precingular 4/5. The invaginated antapical paraplate Y is delineated by folds. Contacts of the antapical paraplate with the dorsal and the ventral surfaces are equal in size.
The apical archeopyle is of (tA)a type, with precingular accessory parasutures. The simple, polyplacoid operculum is adnate to the sulcal ai, and precingular 2 and 1i paraplates.
Dimensions:
According to Drugg (1978): length 65 to 85 µm; width 55 to 65 µm.
This study: holotype, length 74 µm, overall width 60 µm.
Isotypes, 5 specimens measured in µm:
Minimum Mean Maximum
Length: 68 74 80 µm
Overall width: 58 63 72 µm
Holotype: Drugg, 1978, pl.1, fig.1; Masure, 1991, pl.3, figs.1-2; Fensome et al., 1995, fig.1 - p.1701; Fauconnier and Masure, 2004, pl.10, fig.12.
Isotypes: Drugg, 1978
Locus typicus: Reutlingen, Germany
Stratum typicum: Callovian-Early Oxfordian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Drugg 1978, p.63]:
Description:
Cyst five-sided in basic outline and usually bearing from two to five protruding sack-like lobes at the antapex. The position of these lobes is related to the juncture-points of the hypocystal parasutures. Sometimes one or two additional lobes are present higher on the sides of the hypocyst. The archaeopyle is apical and the operculum is six-sided. Five of the sides are of more or less equal length and the sixth side is relatively narrow and fits into the parasulcal notch. The operculum is sometimes attached at the parasulcal notch but is basically of the free type. The paracinigulum and parasulcus are clearly expressed with the former usually delineated by parallel low ridges or folds. Paratabulation is usually indistinct and is marked by folds and by rows of grana and gemmae. Splits often extend downward from the archaeopyle which help to mark the epicystal paratabulation. The antapical paraplate is usually deeply invaginated into the body interior and is positioned within the antapical lobes. The cyst wall, or autophragm, is thin and varies from smooth to faintly granulate. The paracingulum is slightly laevoratory and is about 5 µm wide. The cyst length ranges from about 65 to 85 µm and the width from 55 to 65 µm.
Affinities:
This genus and species is similar in a number of respects to Stephanelytron Sarjeant 1961. The paratabulation seems to be the same except that a posterior intercalary paraplate has not been seen. The lower part of the parasulcus is broad enough, however, to suggest that it may be present even if not confirmed to date. The evaginated antapical lobes and the invaginated antapical paraplate are very likely homologous to the antapical corona of Stephanelytron.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Masure, 1991, p.72, 74, 76:
Diagnosis:
Subsphaeroidal, acavate, proximate dinoflagellate cyst with polygonal outline. Thin wall composed of an autophragm, or an endophragm and periphragm in close contact and with a smooth to faintly granulate surface. Sexiform gonyaulacoid inferred thecal tabulation. Paratabulation incompletely delineated and expressed by folds and penitabular rows of grana or gemmae. Large undifferentiated ventral area. The antapical paraplate is usually deeply invaginated into the body interior. Apical archeopyle, type (tA)a, with accessory precingular parasutures. Simple, polyplacoid operculum adnate with the sulcal ai and precingular 2 and 1i paraplates.
Description:
Slightly dorsoventrally compressed, subspheroidal, acavate, proximate dinocyst with inferred sexiform gonyaulacoid thecal tabulation. Paratabulation is incompletely delineated by folds and penitabular rows of grana and/or gemmae. These elements of relief suggest that the paratabulation is composed of ?0-2 preapical(s) (P,Q), 1 anterior intercalary (K), 4 apicals (1u,B,C,A), 6 precingulars (2-6), X cingulars, 5-?6 postcingulars (?Iu,II-VI), ? 1 posterior intercalary (X), 1 antapical (Y), and X sulcals. The apical ornamentation is weakly expressed. Penitabular adcingular rows of grana or gemmae mark the edges of the precingular paraplates. Two rows of grana or gemmae on folds mark the descending paracingulum. The ventral area is untabulated. The sulcal paraplates and the parasutures between the sulcus and the precingular (2, 1i), postcingular (Iu, II, VI) and posterior intercalary (X) paraplates are not expressed by surface features. Only four postcingular parasutures (II/III, III/IV, IV/V, V/VI) are expressed by penitabular ornament of adjacent paraplates in close contact with one another. The postcingular paraplates III, IV, V are of equal size, IV is below precingular 4 and the postcingular parasuture IV/V is aligned with the precingular 4/5. The invaginated antapical paraplate Y is delineated by folds. Contacts of the antapical paraplate with the dorsal and the ventral surfaces are equal in size.
The apical archeopyle is of (tA)a type, with precingular accessory parasutures. The simple, polyplacoid operculum is adnate to the sulcal ai, and precingular 2 and 1i paraplates.
Dimensions:
According to Drugg (1978): length 65 to 85 µm; width 55 to 65 µm.
This study: holotype, length 74 µm, overall width 60 µm.
Isotypes, 5 specimens measured in µm:
Minimum Mean Maximum
Length: 68 74 80 µm
Overall width: 58 63 72 µm