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Areosphaeridium diktyoplokum
Areosphaeridium diktyoplokus, (Klumpp, 1953); Emendation: Eaton, 1971; Stover and Williams, 1995
Originally Hystrichosphaeridium, subsequently Cordosphaeridium, thirdly (and now) Areosphaeridium.
Tax. sr. synonym of Hystrichosphaeridium (now Areosphaeridium) dictyostilum Menendez, 1965, according to Eaton, 1971. Sarjeant, 1981, retained Hystrichosphaeridium (as Areosphaeridium) dictyostilum as a separate species.
Holotype: Klumpp, 1953, pl.18, fig.3-4; Sarjeant, 1981, pl.6, figs 1,4-5
Paratypes: Klumpp, 1953
Locus typicus: Borehole at Wöhrden, Holstein, Germany
Stratum typicum: Eocene
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Original description as Hystrichosphaeridium diktyoplokus: [Klumpp 1953, p. 392]: (Translation: LPP)
Diagnosis:
A species of the genus Hystrichospaeridium with the next characteristic features: The membrane of the shell is one-layered; more or less reticulate ornamented; the processes are bulges of the membrane.
Description:
The spherical shell is fragile and very transparent. In spite of their slenderness, the processes are merely tubular bulges of the membrane. The processes end in a sort of soft reticulate collar.
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Emended descriptions:
Eaton, 1971, p. 359:
Diagnosis:
The central body has a subcircular to subquadrate outline and a finely granular surface.
The processes are intratabular and have solid fibrous stems of variable length and breadth. Each process terminates in a broad, net-like distal platform which is circular to polygonal in outline with an irregular to entire distal margin. Fenestration may be present in the process stems, producing stem branches and branch complexes. The cingular zone is typically devoid of processes, although occasionally one or two very slender processes may be present on this zone. On the other zones there is one process or branch complex per plate, reflecting the tabulation of 4', 6'', 5-6''', 0-1p, 1''''.
The archaeopyle is apical, tetratabular.
Affinities: (p. 360):
Areosphaeridium diktyoplokus is distinguished from all other species of dinoflagellate cysts by its reflected tabulation, the absence or scarcity of cingular processes, the presence of an apical tetratabular archaeopyle, and the distal complexity of the solid, fibrous processes.
An extensive discussion is given by Eaton, 1971, p. 395-360.
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Stover and Williams, 1995, p. 102:
Description:
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.
Dimensions/Size:
Intermediate to large, not less than 50 µm and may be more than 100 µm in diameter when processes are included.
Affinities:
Despite their brevity, the original diagnosis and description of Areosphaeridium diktyoplokus by Klumpp (1953, p. 392, as Hystrichosphaeridium diktyoplokus) directed attention to the species' salient features. From her text and illustrations, especially pl. 18, figs. 4 and 7, it is evident that Klumpp interpreted the cyst body as having a more or less reticulate sculpturing and as bearing processes with distally expanded, fenestrate frills. The description by Eisenack (1954, p. 68) emphasized the fibrous nature of the processes and their expansion at both ends, but noted in particular that distally the processes expanded into infundibular, fenestrate tips.
Although Evitt elucidated the morphology of Areosphaeridium diktyoplokus at the 1970 Meeting of the American Association of Stratigraphic Palynologists (see abstract by Evitt 1972), details of his observations and interpretations were never published. Consequently, Eaton (1971) was the first to publish a comprehensive description of the species. His emended diagnosis, discussion and illustrations of Areosphaeridium diktyoplokus (ibid, p. 359-360, pl. 1, figs. 3-8; pl. 2, figs. 1-6) demonstrated clearly the relationship between the processes and the paratabulation, the variability of the process stems and terminations as well as their dimensions, and the nature of the archeopyle.
Eaton (1971, p. 359-360) provided the following detailed description of the processes and their terminations: "The distal platform is circular to polygonal in outline, and it may be flat, undulating, or funnel-shaped; the latter form results in the process having an overall infundibular shape ([Eaton 1971] pl. 1, fig. 8). When the platform is polygonal in outline, it is four or five-sided ([Eaton 1971] pl. 1, fig. 7; pl. 2, fig. 4). The distal margin of the platform may be irregular and ragged or entire. The openings in the distal platform are variable in size and distribution. When there are a large number of openings, the distal platform has a net-like appearance ([Eaton 1971], pl. 2, figs. 5, 6), while in some specimens the platforms have few openings, and they are better described as perforated rather than net-like ([Eaton 1971, pl. 1, fig.5). Both large and very small openings may be concentrated near the distal margin of the platform."
"The fibrous nature of the process stems is frequently only discernible in the distal and proximal portion. The stems show variation in length and breadth, and these dimensions are rarely constant in any one specimen. In several specimens the antapical process is the longest ([Eaton 1971] pl. 1, fig. 8), and in some specimens one process may be considerably broader than the others ([Eaton 1971] pl. 1, fig. 6). In its simplest form, the process stem is slightly expanded at its proximal end, relatively uniform in breadth for most of its length, and expanded at its distal end. The distal expansion of the stem into the distal platform is not a uniform, all around expansion, but a broad, blunt bifurcation. In many specimens, some of the process stems are modified by stem fenestrations ([Eaton 1971] pl. 2, fig. 3). This may only be developed in the distal or proximal expanded portions of the stem, and results in the formation of several short, distal or proximal stem branches. In broad stems several fenestrations may be developed."
Our emended description incorporates Eaton's (1971) observations and emphasizes the standard sexiform paratabulation pattern.
Among the specimens of Areosphaeridium diktyoplokus examined by us and whose process distribution was determined with reasonable certainty, we found only one specimen with a paracingular process. All other specimens have 13 processes (17 when opercula are in place), six (or 10) on the epicyst and seven on the hypocyst, and no paracingular processes (text-fig. 1, nos. Al-A2; pl. 1, figs. 2a-b, 4a-b, 6a-c). The seven hypocystal processes represent five postcingular, one posterior intercalary and one antapical paraplate. Specimens with six postcingular processes (1''' present), or without a posterior intercalary (1p) process were not found. Thus we were unable to confirm the variability on the hypocyst expressed by the formula 5-6''', 0-1p, 1'''' (in Eaton 1971).
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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.
Areosphaeridium diktyoplokus (Klumpp, 1953) Eaton, 1971, emend. Stover and Williams, 1995. According to (Stover and Williams (1995, p.102), has typically 17 processes, ten on the epicyst, seven on the hypocyst. Areas between process bases smooth to finely and irregularly granulate. Process stems solid along most of their length. Proximal fibrous ends expanded slightly and merge smoothly with the autophragm surface. Process stems expanded distally into vasiform or infundibular structures with irregular to evenly circular outlines and the fibres of the processes generally separate, so that their walls become fenestrate or even reticulate. On some specimens the vasiform or infundibular distal terminations have irregular or entire margins, whereas on others the terminations are clypeate features whose margins may simulate the shape of underlying individual paraplates. Tabulation is 4', 6", 0-2c, 5"’, 1p, 1"”. There is always a process on 6".
Originally Hystrichosphaeridium, subsequently Cordosphaeridium, thirdly (and now) Areosphaeridium.
Tax. sr. synonym of Hystrichosphaeridium (now Areosphaeridium) dictyostilum Menendez, 1965, according to Eaton, 1971. Sarjeant, 1981, retained Hystrichosphaeridium (as Areosphaeridium) dictyostilum as a separate species.
Holotype: Klumpp, 1953, pl.18, fig.3-4; Sarjeant, 1981, pl.6, figs 1,4-5
Paratypes: Klumpp, 1953
Locus typicus: Borehole at Wöhrden, Holstein, Germany
Stratum typicum: Eocene
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Original description as Hystrichosphaeridium diktyoplokus: [Klumpp 1953, p. 392]: (Translation: LPP)
Diagnosis:
A species of the genus Hystrichospaeridium with the next characteristic features: The membrane of the shell is one-layered; more or less reticulate ornamented; the processes are bulges of the membrane.
Description:
The spherical shell is fragile and very transparent. In spite of their slenderness, the processes are merely tubular bulges of the membrane. The processes end in a sort of soft reticulate collar.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended descriptions:
Eaton, 1971, p. 359:
Diagnosis:
The central body has a subcircular to subquadrate outline and a finely granular surface.
The processes are intratabular and have solid fibrous stems of variable length and breadth. Each process terminates in a broad, net-like distal platform which is circular to polygonal in outline with an irregular to entire distal margin. Fenestration may be present in the process stems, producing stem branches and branch complexes. The cingular zone is typically devoid of processes, although occasionally one or two very slender processes may be present on this zone. On the other zones there is one process or branch complex per plate, reflecting the tabulation of 4', 6'', 5-6''', 0-1p, 1''''.
The archaeopyle is apical, tetratabular.
Affinities: (p. 360):
Areosphaeridium diktyoplokus is distinguished from all other species of dinoflagellate cysts by its reflected tabulation, the absence or scarcity of cingular processes, the presence of an apical tetratabular archaeopyle, and the distal complexity of the solid, fibrous processes.
An extensive discussion is given by Eaton, 1971, p. 395-360.
-------------------------------------------------
Stover and Williams, 1995, p. 102:
Description:
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.
Dimensions/Size:
Intermediate to large, not less than 50 µm and may be more than 100 µm in diameter when processes are included.
Affinities:
Despite their brevity, the original diagnosis and description of Areosphaeridium diktyoplokus by Klumpp (1953, p. 392, as Hystrichosphaeridium diktyoplokus) directed attention to the species' salient features. From her text and illustrations, especially pl. 18, figs. 4 and 7, it is evident that Klumpp interpreted the cyst body as having a more or less reticulate sculpturing and as bearing processes with distally expanded, fenestrate frills. The description by Eisenack (1954, p. 68) emphasized the fibrous nature of the processes and their expansion at both ends, but noted in particular that distally the processes expanded into infundibular, fenestrate tips.
Although Evitt elucidated the morphology of Areosphaeridium diktyoplokus at the 1970 Meeting of the American Association of Stratigraphic Palynologists (see abstract by Evitt 1972), details of his observations and interpretations were never published. Consequently, Eaton (1971) was the first to publish a comprehensive description of the species. His emended diagnosis, discussion and illustrations of Areosphaeridium diktyoplokus (ibid, p. 359-360, pl. 1, figs. 3-8; pl. 2, figs. 1-6) demonstrated clearly the relationship between the processes and the paratabulation, the variability of the process stems and terminations as well as their dimensions, and the nature of the archeopyle.
Eaton (1971, p. 359-360) provided the following detailed description of the processes and their terminations: "The distal platform is circular to polygonal in outline, and it may be flat, undulating, or funnel-shaped; the latter form results in the process having an overall infundibular shape ([Eaton 1971] pl. 1, fig. 8). When the platform is polygonal in outline, it is four or five-sided ([Eaton 1971] pl. 1, fig. 7; pl. 2, fig. 4). The distal margin of the platform may be irregular and ragged or entire. The openings in the distal platform are variable in size and distribution. When there are a large number of openings, the distal platform has a net-like appearance ([Eaton 1971], pl. 2, figs. 5, 6), while in some specimens the platforms have few openings, and they are better described as perforated rather than net-like ([Eaton 1971, pl. 1, fig.5). Both large and very small openings may be concentrated near the distal margin of the platform."
"The fibrous nature of the process stems is frequently only discernible in the distal and proximal portion. The stems show variation in length and breadth, and these dimensions are rarely constant in any one specimen. In several specimens the antapical process is the longest ([Eaton 1971] pl. 1, fig. 8), and in some specimens one process may be considerably broader than the others ([Eaton 1971] pl. 1, fig. 6). In its simplest form, the process stem is slightly expanded at its proximal end, relatively uniform in breadth for most of its length, and expanded at its distal end. The distal expansion of the stem into the distal platform is not a uniform, all around expansion, but a broad, blunt bifurcation. In many specimens, some of the process stems are modified by stem fenestrations ([Eaton 1971] pl. 2, fig. 3). This may only be developed in the distal or proximal expanded portions of the stem, and results in the formation of several short, distal or proximal stem branches. In broad stems several fenestrations may be developed."
Our emended description incorporates Eaton's (1971) observations and emphasizes the standard sexiform paratabulation pattern.
Among the specimens of Areosphaeridium diktyoplokus examined by us and whose process distribution was determined with reasonable certainty, we found only one specimen with a paracingular process. All other specimens have 13 processes (17 when opercula are in place), six (or 10) on the epicyst and seven on the hypocyst, and no paracingular processes (text-fig. 1, nos. Al-A2; pl. 1, figs. 2a-b, 4a-b, 6a-c). The seven hypocystal processes represent five postcingular, one posterior intercalary and one antapical paraplate. Specimens with six postcingular processes (1''' present), or without a posterior intercalary (1p) process were not found. Thus we were unable to confirm the variability on the hypocyst expressed by the formula 5-6''', 0-1p, 1'''' (in Eaton 1971).
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Areosphaeridium diktyoplokus (Klumpp, 1953) Eaton, 1971, emend. Stover and Williams, 1995. According to (Stover and Williams (1995, p.102), has typically 17 processes, ten on the epicyst, seven on the hypocyst. Areas between process bases smooth to finely and irregularly granulate. Process stems solid along most of their length. Proximal fibrous ends expanded slightly and merge smoothly with the autophragm surface. Process stems expanded distally into vasiform or infundibular structures with irregular to evenly circular outlines and the fibres of the processes generally separate, so that their walls become fenestrate or even reticulate. On some specimens the vasiform or infundibular distal terminations have irregular or entire margins, whereas on others the terminations are clypeate features whose margins may simulate the shape of underlying individual paraplates. Tabulation is 4', 6", 0-2c, 5"’, 1p, 1"”. There is always a process on 6".