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Atopodinium
From Williams et al., 2017:
[Atopodinium Drugg, 1978, p. 62; Emendations: Masure, 1991, p.64-65; Slimani, 2004, p.182
Type species: Atopodinium prostatum, Drugg, 1978 (pl.1, fig.1)]
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Original description: [Drugg, 1978]:
Diagnosis:
Cyst basically five-sided in outline and dorso-ventrally flattened. The parasulcus and paracingulum are clearly expressed and the archaeopyle is apical. Although not clearly expressed the paratabulation appears to be 1`, 5``, Xc, 5```, 1````. The antapex usually exhibits from two to five everted lobes and the antapical paraplate is invaginated.
Affinities:
Atopodinium differs from Stephanelytron in basic outline and in lacking processes.
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Modified description:
Stover and Williams 1987, p. 29-30:
Synopsis:
Cysts proximate, compressed peridinioid with the antapical margin lobate and shorter than other margins; autophragm with parasutural folds or rows of low relief features apparently indicating a paratabulation of 1`, 5``, Xc, 5```, 1````; archeopyle apical, operculum normally free and apparently representing a single paraplate.
Description:
Shape: Compressed peridinioid and usually bearing 2 to 5 antapical lobes.
Wall relationships: Autophragm only.
Wall features: Autophragm smooth or granular, and with parasutural folds or rows of features with low relief.
Archeopyle: Apical, principal archeopyle suture outlines a hexagonal opening; operculum evidently represents a single paraplate that is normally free but may be connected ventrally on some specimens.
Paratabulation: Usually indistinct; indicated by parasutural features and additionally by accessory archeopyle sutures; formula apparently 1`, 5``, Xc, 5```, 1````.
Paracingulum: Indicated by parallel, transverse, low folds or ridges; undivided.
Parasulcus: Indicated by longitudinal depression.
Size: Intermediate, about 65 µm to 85 µm in length
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Emended description:
Masure, 1991:
Diagnosis:
Subspheroidal, acavate, proximochorate to chorate dinoflagellate cyst, polygonal to oval in outline. Wall composed of an autophragm or of an endophragm and a periphragm in close contact, with a smooth to granulate outer surface. Sexiform gonyaulacoid inferred thecal tabulation. Paratabulation incompletely delineated (0?2 preapicals, 4 apicals, 0-1 anterior intercalary, 6 precingulars, X cingulars, 5-?6 postcingulars, ?1 posterior intercalary, 1 antapical, X sulcals) indicated by penitabular grana, folds, septa or apparently processes. Large non-ornamented ventral area, with partial or total obliteration of ornamental features on A, 1u, 2, 1i, Iu and sulcal paraplates .The parasutural features on the hypocyst result from the close contact of penitabular relief between adjacent paraplates. Only four postcingular parasutures are delineated by ornament: II/III, III/IV, IV/V, V/VI. The postcingular paraplates III, IV, V, are of equal size, and parasuture 4/5 is aligned with IV/V.
Apical archeopyle, type (tA)a, with precingular accessory parasutures.
Operculum simple, polyplacoid, adnate with the sulcal ai and precingular (2,1i) paraplates.
Description:
Shape: Subspheroidal cyst with slight dorso-ventral compression, oval to polygonal in outline, with or without a preapical process, and acavate, proximochorate to chorate.
Wall: Composed of thin autophragm or of a thin endophragm and periphragm in close contact.
Surface Relief: The outer surface of the wall is smooth to scabrate and granulate. Ornamentation variable and consists of folds, grana, gemmae, septa or processes. Septa and/or processes are smooth, granulate, striate or perforated. The distal ends of the septa are smooth, denticulate or with deep splits. The interruption of septate membranes by deep splits give rise to the processes.
Paratabulation: Sexiform gonyaulacoid inferred thecal tabulation. Paratabulation incompletely delineated by high or low penitabular relief. The paratabulation shown by ornamental features consists of 0-?2 preapical(s) (P,?Q), 4 apicals (1u, B, C, A), 0-1 anterior intercalary (K), 6 precingulars (1i, 2-6), X cingulars, 5-?6 postcingulars (?lu, IIVI), ? 1 posterior intercalary (X), 1 antapical (Y), X sulcals. The preapical paraplate(s) P and Q? may form a process. Processes may be present or absent on the apical paraplates. The surface ornament on the precingular paraplates is penitabular adcingular, while that on the hypocyst gives the appearance of parasutural features; however, the parasutural features result from the close contact of penitabular relief of adjacent paraplates. Only four postcingular parasutures are marked: II/III, III/IV, IV/V, V/VI. Postcingular paraplates III, IV and V are equal in size; postcingular IV lies below the precingular 4. The 4/5 parasuture is aligned with IV/V. The position of the contact Y/IV is mid-dorsal. Contacts of the antapical paraplate Y with the ventral and dorsal surfaces are equal in size or the dorsal contact is shorter than the ventral one.
Paracingulum: Descending, marked by penitabular or intratabular relief features. The intratabular ornament result from the contact of two penitabular ornaments.
Parasulcus: The ventral arrangement is of the A/ai type. The sulcal paraplates and the parasutures that are shared between sulcal and precingular (2, 1i) paraplates, and between postcingular (Iu, II, VI) and posterior intercalary (X) paraplates, are not expressed by surface features.
Archeopyle: Apical, type (tA)a, with well developed precingular accessory parasutures. Simple, polyplacoid operculum adnate, attached to the sulcal (ai) and precingular (2, li) paraplates.
Dimensions:
60 to 100 µm (determined from specimens of the type species of Atopodinium).
Remarks:
The ventral paraplate arrangement (Helenes, 1986) of Atopodinium is not visible under the optical microscope because this area is weakly ornamented. Additional type residue is not available for SEM study which might elucidate these arrangements (personal commun., W.S. Drugg, 1988). Under the electron microscope, one specimen of Atopodinium haromense (=Marhrebinia breviornata Masure, 1988) displays a ventral arrangement of the A/ai type (Plate 4, fig.13; Text-Figure 2). Evitt (1985) and Helenes (1986, p. 81) note that the A/ai arrangement is commonly combined with a partial or total obliteration of parasuture A/lu, and occasionally obliteration of relief features on A, 1u, 2, 1i, Iu, and sulcal paraplates.
Affinities:
Atopodinium differs significantly from Stephanelytron Sarjeant 1961 in shape and Atopodinium has an autophragm rather than an autophragm and ectophragm as in Stephanelytron.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Atopodinium Drugg, 1971, emend. Masure, 1978, has autophragm or endophragm and periphragm in close contact. Sexiform tabulation incompletely expressed 0-2 pr, 4`, 0-1 ai, 6", xc, 5-?6"' , 1p, 1"'', xs. Indicated by penitabular folds, septa or apparently processes. Ornament reduced on 4`, 1`, 1", 6", 1"' and sulcals. Only four postcingular plates delineated by ornamentation. Parasuture 3"/4" is aligned with 4"' /5"' . Archeopyle apical, attached and with precingular accessory sutures.
[Atopodinium Drugg, 1978, p. 62; Emendations: Masure, 1991, p.64-65; Slimani, 2004, p.182
Type species: Atopodinium prostatum, Drugg, 1978 (pl.1, fig.1)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Drugg, 1978]:
Diagnosis:
Cyst basically five-sided in outline and dorso-ventrally flattened. The parasulcus and paracingulum are clearly expressed and the archaeopyle is apical. Although not clearly expressed the paratabulation appears to be 1`, 5``, Xc, 5```, 1````. The antapex usually exhibits from two to five everted lobes and the antapical paraplate is invaginated.
Affinities:
Atopodinium differs from Stephanelytron in basic outline and in lacking processes.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Williams 1987, p. 29-30:
Synopsis:
Cysts proximate, compressed peridinioid with the antapical margin lobate and shorter than other margins; autophragm with parasutural folds or rows of low relief features apparently indicating a paratabulation of 1`, 5``, Xc, 5```, 1````; archeopyle apical, operculum normally free and apparently representing a single paraplate.
Description:
Shape: Compressed peridinioid and usually bearing 2 to 5 antapical lobes.
Wall relationships: Autophragm only.
Wall features: Autophragm smooth or granular, and with parasutural folds or rows of features with low relief.
Archeopyle: Apical, principal archeopyle suture outlines a hexagonal opening; operculum evidently represents a single paraplate that is normally free but may be connected ventrally on some specimens.
Paratabulation: Usually indistinct; indicated by parasutural features and additionally by accessory archeopyle sutures; formula apparently 1`, 5``, Xc, 5```, 1````.
Paracingulum: Indicated by parallel, transverse, low folds or ridges; undivided.
Parasulcus: Indicated by longitudinal depression.
Size: Intermediate, about 65 µm to 85 µm in length
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Emended description:
Masure, 1991:
Diagnosis:
Subspheroidal, acavate, proximochorate to chorate dinoflagellate cyst, polygonal to oval in outline. Wall composed of an autophragm or of an endophragm and a periphragm in close contact, with a smooth to granulate outer surface. Sexiform gonyaulacoid inferred thecal tabulation. Paratabulation incompletely delineated (0?2 preapicals, 4 apicals, 0-1 anterior intercalary, 6 precingulars, X cingulars, 5-?6 postcingulars, ?1 posterior intercalary, 1 antapical, X sulcals) indicated by penitabular grana, folds, septa or apparently processes. Large non-ornamented ventral area, with partial or total obliteration of ornamental features on A, 1u, 2, 1i, Iu and sulcal paraplates .The parasutural features on the hypocyst result from the close contact of penitabular relief between adjacent paraplates. Only four postcingular parasutures are delineated by ornament: II/III, III/IV, IV/V, V/VI. The postcingular paraplates III, IV, V, are of equal size, and parasuture 4/5 is aligned with IV/V.
Apical archeopyle, type (tA)a, with precingular accessory parasutures.
Operculum simple, polyplacoid, adnate with the sulcal ai and precingular (2,1i) paraplates.
Description:
Shape: Subspheroidal cyst with slight dorso-ventral compression, oval to polygonal in outline, with or without a preapical process, and acavate, proximochorate to chorate.
Wall: Composed of thin autophragm or of a thin endophragm and periphragm in close contact.
Surface Relief: The outer surface of the wall is smooth to scabrate and granulate. Ornamentation variable and consists of folds, grana, gemmae, septa or processes. Septa and/or processes are smooth, granulate, striate or perforated. The distal ends of the septa are smooth, denticulate or with deep splits. The interruption of septate membranes by deep splits give rise to the processes.
Paratabulation: Sexiform gonyaulacoid inferred thecal tabulation. Paratabulation incompletely delineated by high or low penitabular relief. The paratabulation shown by ornamental features consists of 0-?2 preapical(s) (P,?Q), 4 apicals (1u, B, C, A), 0-1 anterior intercalary (K), 6 precingulars (1i, 2-6), X cingulars, 5-?6 postcingulars (?lu, IIVI), ? 1 posterior intercalary (X), 1 antapical (Y), X sulcals. The preapical paraplate(s) P and Q? may form a process. Processes may be present or absent on the apical paraplates. The surface ornament on the precingular paraplates is penitabular adcingular, while that on the hypocyst gives the appearance of parasutural features; however, the parasutural features result from the close contact of penitabular relief of adjacent paraplates. Only four postcingular parasutures are marked: II/III, III/IV, IV/V, V/VI. Postcingular paraplates III, IV and V are equal in size; postcingular IV lies below the precingular 4. The 4/5 parasuture is aligned with IV/V. The position of the contact Y/IV is mid-dorsal. Contacts of the antapical paraplate Y with the ventral and dorsal surfaces are equal in size or the dorsal contact is shorter than the ventral one.
Paracingulum: Descending, marked by penitabular or intratabular relief features. The intratabular ornament result from the contact of two penitabular ornaments.
Parasulcus: The ventral arrangement is of the A/ai type. The sulcal paraplates and the parasutures that are shared between sulcal and precingular (2, 1i) paraplates, and between postcingular (Iu, II, VI) and posterior intercalary (X) paraplates, are not expressed by surface features.
Archeopyle: Apical, type (tA)a, with well developed precingular accessory parasutures. Simple, polyplacoid operculum adnate, attached to the sulcal (ai) and precingular (2, li) paraplates.
Dimensions:
60 to 100 µm (determined from specimens of the type species of Atopodinium).
Remarks:
The ventral paraplate arrangement (Helenes, 1986) of Atopodinium is not visible under the optical microscope because this area is weakly ornamented. Additional type residue is not available for SEM study which might elucidate these arrangements (personal commun., W.S. Drugg, 1988). Under the electron microscope, one specimen of Atopodinium haromense (=Marhrebinia breviornata Masure, 1988) displays a ventral arrangement of the A/ai type (Plate 4, fig.13; Text-Figure 2). Evitt (1985) and Helenes (1986, p. 81) note that the A/ai arrangement is commonly combined with a partial or total obliteration of parasuture A/lu, and occasionally obliteration of relief features on A, 1u, 2, 1i, Iu, and sulcal paraplates.
Affinities:
Atopodinium differs significantly from Stephanelytron Sarjeant 1961 in shape and Atopodinium has an autophragm rather than an autophragm and ectophragm as in Stephanelytron.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Atopodinium Drugg, 1971, emend. Masure, 1978, has autophragm or endophragm and periphragm in close contact. Sexiform tabulation incompletely expressed 0-2 pr, 4`, 0-1 ai, 6", xc, 5-?6"' , 1p, 1"'', xs. Indicated by penitabular folds, septa or apparently processes. Ornament reduced on 4`, 1`, 1", 6", 1"' and sulcals. Only four postcingular plates delineated by ornamentation. Parasuture 3"/4" is aligned with 4"' /5"' . Archeopyle apical, attached and with precingular accessory sutures.