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Areosphaeridium
From Fensome et al., 2019:
Areosphaeridium, Eaton, 1971, p.357–358.
Emendation: Stover and Williams, 1995, p.100.
Type: Klumpp, 1953, pl.18, figs.3–4, as Hystrichosphaeridium diktyoplokum.
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Original description: [Eaton ,1971]:
Description:
Dinoflagellate cyst having a central body which is sub-circular to sub-quadrate in outline, with a finely granular surface, bearing solid, fibrous, intratabular processes. The process stems may be simple or branched, and frequently show fenestration. Distally the process stems are expanded and they terminate either as a distal bifurcation or a broad distal platform. Processes are invariably present on the apical, pre- and postcingular, and apical zones. Processes may or may not be present on the cingular zone. There is typically one process per plate, although some plates may be devoid of processes, and others may have two or three processes.
The reflected paratabulation is 4`, 5-6``, 5-6```, 0-1 p, 1````.
The archeopyle is apical tetratabular.
Affinities:
Areosphaeridium shows some similarity to three other genera: Oligosphaeridium Davey and Williams 1966, Cordosphaeridium Eisenack, 1963 emend Morgenroth 1968, and Cyclonephelium Deflandre and Cookson 1955 emend. Williams and Downie 1966. Oligosphaeridium has a reflected tabulation similar to that of Areosphaeridium but is distinguished by having non-fibrous tubiform processes, and there are no processes on the cingular zone. Cordosphaeridium has fibrous processes but they are distally less complex than those of Areosphaeridium. Cordosphaeridium is also distinguished by having a precingular archeopyle, and processes on all plates in the cingular zone. When processes are present on the lateral margins of the cingular zone in Areosphaeridium, the overall distribution of all the processes is very similar to that of Cyclonephelium. However, in Cyclonephelium there is usually more than one process per plate, and if not, the processes are complexly branched, and are frequently distally united.
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Modified description:
Stover and Evitt 1978, p. 19-20:
Synopsis:
Cysts skolochorate, gonyaulacacean; body subspherical to lenticular with 17 to 24 solid intratabular processes; paracingular processes present or absent; distal terminations of processes platformlike and perforate, or arcuate and denticulate; archeopyle apical, Type tA.
Description:
Shape: Body subspherical to lenticular.
Wall relationships: Autophragm only, except when expanded process tips are construed as ectophragm.
Wall features: No parasutural features. Intratabular processes solid, generally fibrous, slender, expanded distally; distal terminations platformlike and perforate, or arcuate and denticulate. Autophragm smooth or finely granulate between processes.
Paratabulation: Indicated by intratabular processes; gonyaulacacean, process formula: 0-1pr, 3-4`, 5-6``, 0 or 4-7c, 5-6```, 0-1p, 1````, 0-3s. Typically one process per paraplate, but some may lack processes. Archeopyle and operculum margins indicate four apical paraplates, and six precingular paraplates are always present.
Archeopyle: Apical, Type tA; principal archeopyle suture zigzag; operculum free.
Paracingulum: Indicated by absence of processes, or by transverse alignment of four to seven processes.
Parasulcus: Apical position indicated occasionally by sulcal notch that is offset in species with lenticular bodies; parasulcal area may lack processes, or have up to three processes on the hypocyst.
Size: Intermediate to large.
Affinities:
Areosphaeridium differs from Hystrichosphaeridium and Oligosphaeridium in having solid, generally fibrous processes rather than tubular, nonfibrous processes. The body and processes of Eatonicysta and Areosphaeridium are essentially identical; however, the processes of former are connected distally by an ectophragm that is not present in Areosphaeridium. Surculosphaeridium differs from Areosphaeridium in lacking fenestrate platformlike or arcuate features at the ends of the processes.
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Emended description:
Stover and Williams, 1995:
Synopsis: Cysts skolochorate, central body subspherical or slightly flattened dorso-ventrally and bearing 17 to 23 intratabular processes; processes solid, commonly fibroid with expanded, variously shaped (generally vasiform, infundibular or clypeate), fenestrate to reticulate tips; epicyst with nine or 10 processes (4`, 5-6``), hypocyst almost always with seven processes (5```, 1p, 1````) arranged in the standard sexiform pattern; paraplate 1" is wider than 6"; up to six paracingular processes may be present; archeopyle apical, operculum tetratabular, simple and free.
Descripton:
Shape: Cysts skolochorate, central body subspherical or slightly flattened dorso-ventrally.
Wall relationships: Autophragm only.
Wall features: Autophragm smooth or inconspicuously and uniformly ornamented between processes with features of low relief; intratabular process stems solid and may be fibroid for at least part of their length; tips branched or expanded into fenestrate to reticulate vasiform, infundibular or clypeate features with irregular or even margins, the latter may simulate the outlines of reflected paraplates.
Excystment mode: Archeopyle apical; operculum tetratabular, simple and free.
Paratabulation: Gonyaulacoid, indicated on the epicyst by archeopyle sutures and the locations of intratabular processes, elsewhere on the central body by process locations only; generally one process per paraplate, but some paraplates may lack processes and, rarely, others may have two. Process formula: 4`, 5-6``, 0-6c, 5```, 1p, 1````, 0s. First precingular paraplate wider than the sixth. Hypocyst virtually always with seven processes (5```, 1p, 1````) consistently arranged in the standard sexiform configuration.
Paracingulum: Indicated by the absence of processes or by the presence of up to six intratabular processes; paracingular processes generally narrower and with less complex distal structures than the processes situated elsewhere on the cysts.
Parasulcus: Anterior position indicated by parasulcal notch which may be offset slightly; parasulcal processes absent.
Size: Intermediate to large, not less than 50 µm and may be more than 100 µm in diameter when processes are included.
Remarks:
As described by Eaton (1971, p. 257-258), Areosphaeridium included forms with subspherical to subquadrate central bodies which bear solid, fibroid intratabular processes with simple or branched stems and with some kind of fenestrate terminations. Typically, each paraplate possesses one intratabular process, but some lack processes and others were said to have more than one process. A process formula of 4`, 5-6``, 5-6```, 0-1p, 1```` accounted for the general paratabulation. However, the formula failed to acknowledge certain details. For example, the presence of paracingular processes on some species was not indicated, nor were the paraplate equivalents identified for the "extra" hypocystal processes (labeled "x" by Eaton). The archeopyle was recognized as apical, type [4A], with a free operculum.
The synopsis and modified description for Areosphaeridium presented by Stover and Evitt (1978, p. 19-20) re-iterated the salient generic characteristics indicated by Eaton ( 1971 ) and added that the central bodies could be lenticular as well as subspherical or subquadrate. In addition, their process formula allowed for minor variation in the number of processes. Since then no generic emendation or modification has been proposed. We emend Areosphaeridium to include only the type species Areosphaeridium diktyoplokus, whose hypocystal paratabulation pattern is standard gonyaulacacean sexiform (text-fig. 1, no. A2). Paraplate 1`` is wider than 6`` (text-fig. 1, no. A1) and paracingular processes may be present or absent.
Affinities:
Areosphaeridium differs from Eatonicysta Stover and Evitt 1978 emended herein in always having solid processes and in lacking an enclosing ectophragm which also connects the tips of processes; otherwise the basic morphology of the two genera is identical. The presence of solid and fibroid processes as well as the generally more complex distal termination of the processes serves to separate this genus from other skolochorate genera with subspherical bodies, apical archeopyles and standard sexiform hypocystal patterns such as Emmetrocysta Stover 1975, Cooksonidium gen. nov., Hystrichosphaeridium Deflandre 1937 emended Davey and Williams 1966 and Oligosphaeridium Davey and Williams 1966 emended Davey 1982. Emmetrocysta has intratabular process complexes with the tips of each complex connected by a ring trabeculae; Cooksonidium has both single processes and process complexes without clypeate terminations and both Hystrichosphaeridium and Oligosphaeridium have hollow processes usually with aculeate tips, or simply expanded or branched tips, respectively. The presence or absence of cingular processes is crucial to the separation of Hystrichosphaeridium and Oligosphaeridium. In Areosphaeridium the presence or absence of cingular processes is variable, although Areosphaeridium diktyoplokus rarely possesses such processes. Areosphaeridium differs from Enneadocysta by having a sexiform rather than a partiforrn hypocystal paratabulation configuration and by having most processes with other than licrate tips.
Areosphaeridium, Eaton, 1971, p.357–358.
Emendation: Stover and Williams, 1995, p.100.
Type: Klumpp, 1953, pl.18, figs.3–4, as Hystrichosphaeridium diktyoplokum.
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Original description: [Eaton ,1971]:
Description:
Dinoflagellate cyst having a central body which is sub-circular to sub-quadrate in outline, with a finely granular surface, bearing solid, fibrous, intratabular processes. The process stems may be simple or branched, and frequently show fenestration. Distally the process stems are expanded and they terminate either as a distal bifurcation or a broad distal platform. Processes are invariably present on the apical, pre- and postcingular, and apical zones. Processes may or may not be present on the cingular zone. There is typically one process per plate, although some plates may be devoid of processes, and others may have two or three processes.
The reflected paratabulation is 4`, 5-6``, 5-6```, 0-1 p, 1````.
The archeopyle is apical tetratabular.
Affinities:
Areosphaeridium shows some similarity to three other genera: Oligosphaeridium Davey and Williams 1966, Cordosphaeridium Eisenack, 1963 emend Morgenroth 1968, and Cyclonephelium Deflandre and Cookson 1955 emend. Williams and Downie 1966. Oligosphaeridium has a reflected tabulation similar to that of Areosphaeridium but is distinguished by having non-fibrous tubiform processes, and there are no processes on the cingular zone. Cordosphaeridium has fibrous processes but they are distally less complex than those of Areosphaeridium. Cordosphaeridium is also distinguished by having a precingular archeopyle, and processes on all plates in the cingular zone. When processes are present on the lateral margins of the cingular zone in Areosphaeridium, the overall distribution of all the processes is very similar to that of Cyclonephelium. However, in Cyclonephelium there is usually more than one process per plate, and if not, the processes are complexly branched, and are frequently distally united.
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Modified description:
Stover and Evitt 1978, p. 19-20:
Synopsis:
Cysts skolochorate, gonyaulacacean; body subspherical to lenticular with 17 to 24 solid intratabular processes; paracingular processes present or absent; distal terminations of processes platformlike and perforate, or arcuate and denticulate; archeopyle apical, Type tA.
Description:
Shape: Body subspherical to lenticular.
Wall relationships: Autophragm only, except when expanded process tips are construed as ectophragm.
Wall features: No parasutural features. Intratabular processes solid, generally fibrous, slender, expanded distally; distal terminations platformlike and perforate, or arcuate and denticulate. Autophragm smooth or finely granulate between processes.
Paratabulation: Indicated by intratabular processes; gonyaulacacean, process formula: 0-1pr, 3-4`, 5-6``, 0 or 4-7c, 5-6```, 0-1p, 1````, 0-3s. Typically one process per paraplate, but some may lack processes. Archeopyle and operculum margins indicate four apical paraplates, and six precingular paraplates are always present.
Archeopyle: Apical, Type tA; principal archeopyle suture zigzag; operculum free.
Paracingulum: Indicated by absence of processes, or by transverse alignment of four to seven processes.
Parasulcus: Apical position indicated occasionally by sulcal notch that is offset in species with lenticular bodies; parasulcal area may lack processes, or have up to three processes on the hypocyst.
Size: Intermediate to large.
Affinities:
Areosphaeridium differs from Hystrichosphaeridium and Oligosphaeridium in having solid, generally fibrous processes rather than tubular, nonfibrous processes. The body and processes of Eatonicysta and Areosphaeridium are essentially identical; however, the processes of former are connected distally by an ectophragm that is not present in Areosphaeridium. Surculosphaeridium differs from Areosphaeridium in lacking fenestrate platformlike or arcuate features at the ends of the processes.
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Emended description:
Stover and Williams, 1995:
Synopsis: Cysts skolochorate, central body subspherical or slightly flattened dorso-ventrally and bearing 17 to 23 intratabular processes; processes solid, commonly fibroid with expanded, variously shaped (generally vasiform, infundibular or clypeate), fenestrate to reticulate tips; epicyst with nine or 10 processes (4`, 5-6``), hypocyst almost always with seven processes (5```, 1p, 1````) arranged in the standard sexiform pattern; paraplate 1" is wider than 6"; up to six paracingular processes may be present; archeopyle apical, operculum tetratabular, simple and free.
Descripton:
Shape: Cysts skolochorate, central body subspherical or slightly flattened dorso-ventrally.
Wall relationships: Autophragm only.
Wall features: Autophragm smooth or inconspicuously and uniformly ornamented between processes with features of low relief; intratabular process stems solid and may be fibroid for at least part of their length; tips branched or expanded into fenestrate to reticulate vasiform, infundibular or clypeate features with irregular or even margins, the latter may simulate the outlines of reflected paraplates.
Excystment mode: Archeopyle apical; operculum tetratabular, simple and free.
Paratabulation: Gonyaulacoid, indicated on the epicyst by archeopyle sutures and the locations of intratabular processes, elsewhere on the central body by process locations only; generally one process per paraplate, but some paraplates may lack processes and, rarely, others may have two. Process formula: 4`, 5-6``, 0-6c, 5```, 1p, 1````, 0s. First precingular paraplate wider than the sixth. Hypocyst virtually always with seven processes (5```, 1p, 1````) consistently arranged in the standard sexiform configuration.
Paracingulum: Indicated by the absence of processes or by the presence of up to six intratabular processes; paracingular processes generally narrower and with less complex distal structures than the processes situated elsewhere on the cysts.
Parasulcus: Anterior position indicated by parasulcal notch which may be offset slightly; parasulcal processes absent.
Size: Intermediate to large, not less than 50 µm and may be more than 100 µm in diameter when processes are included.
Remarks:
As described by Eaton (1971, p. 257-258), Areosphaeridium included forms with subspherical to subquadrate central bodies which bear solid, fibroid intratabular processes with simple or branched stems and with some kind of fenestrate terminations. Typically, each paraplate possesses one intratabular process, but some lack processes and others were said to have more than one process. A process formula of 4`, 5-6``, 5-6```, 0-1p, 1```` accounted for the general paratabulation. However, the formula failed to acknowledge certain details. For example, the presence of paracingular processes on some species was not indicated, nor were the paraplate equivalents identified for the "extra" hypocystal processes (labeled "x" by Eaton). The archeopyle was recognized as apical, type [4A], with a free operculum.
The synopsis and modified description for Areosphaeridium presented by Stover and Evitt (1978, p. 19-20) re-iterated the salient generic characteristics indicated by Eaton ( 1971 ) and added that the central bodies could be lenticular as well as subspherical or subquadrate. In addition, their process formula allowed for minor variation in the number of processes. Since then no generic emendation or modification has been proposed. We emend Areosphaeridium to include only the type species Areosphaeridium diktyoplokus, whose hypocystal paratabulation pattern is standard gonyaulacacean sexiform (text-fig. 1, no. A2). Paraplate 1`` is wider than 6`` (text-fig. 1, no. A1) and paracingular processes may be present or absent.
Affinities:
Areosphaeridium differs from Eatonicysta Stover and Evitt 1978 emended herein in always having solid processes and in lacking an enclosing ectophragm which also connects the tips of processes; otherwise the basic morphology of the two genera is identical. The presence of solid and fibroid processes as well as the generally more complex distal termination of the processes serves to separate this genus from other skolochorate genera with subspherical bodies, apical archeopyles and standard sexiform hypocystal patterns such as Emmetrocysta Stover 1975, Cooksonidium gen. nov., Hystrichosphaeridium Deflandre 1937 emended Davey and Williams 1966 and Oligosphaeridium Davey and Williams 1966 emended Davey 1982. Emmetrocysta has intratabular process complexes with the tips of each complex connected by a ring trabeculae; Cooksonidium has both single processes and process complexes without clypeate terminations and both Hystrichosphaeridium and Oligosphaeridium have hollow processes usually with aculeate tips, or simply expanded or branched tips, respectively. The presence or absence of cingular processes is crucial to the separation of Hystrichosphaeridium and Oligosphaeridium. In Areosphaeridium the presence or absence of cingular processes is variable, although Areosphaeridium diktyoplokus rarely possesses such processes. Areosphaeridium differs from Enneadocysta by having a sexiform rather than a partiforrn hypocystal paratabulation configuration and by having most processes with other than licrate tips.