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Enneadocysta fenestrata
Enneadocysta fenestrata (Bujak, 1976) emend. Stover and Williams, 1995
originally Areosphaeridium, subsequently and now Enneadocysta
Holotype: Bujak 1976: Plate III, fig. 2
Locus typicus: Whitecliff Bay, Isle of Wight, England.
Stratum typicum: Middle Barton Beds (Upper Eocene)
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Enneadocysta fenestrata (Bujak, 1976) Stover and Williams, 1995, emend. Stover and Williams, 1995. Autophragm scabrate to granular with 21 to 23 processes, 9 on the epicyst, eight on the hypocyst, and four to six paracingulars. Processes with solid, relatively narrow stems, and reticulate, clypeate tips, whose margins may be irregularly ragged to subcircular or entire and polygonal. Some adjacent processes may be connected by trabeculae. Outline of process tips with entire margins may simulate the shape of the plates. Process formula: 4', 5" (no process on plate 6"), 4-6c, 5"’, 1p, 2"”. Size: central body length (without operculum) 44 µm, width 30-46 µm, process length 14-23 µm.
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Original diagnosis: Bujak 1976, p. 107: Areosphaeridium fenestratum
Central body dorsoventrally compressed, outline subcircular to subquadrate. Autophragm scabrate to granulate, forming intratabular processes with solid, fibrous stems. Processes distally bifurcate or branched, bearing platforms formed of interconnecting trabeculae. Platforms of adjacent processes sometimes connected by trabeculae. Reflected process tabulation 4',5",xc,5"',1p,1""; plate areas 6 , 6"', anterior sulcal area, and mid-dorsal and mid-ventral areas without processes. Elsewhere one process per plate area, except near antapex where additional processes sometimes present, and on lateral cingular margins where four to nine processes always present. Archeopyle apical, tetratabular. Operculum simple and usually detached. Short accessory archeopyle sutures often partially defining six precingular plate areas, and an anterior sulcal plate area offset to the left on the ventral surface.
Dimensions: Holotype, central body length (without operculum) 33Ám, central body breadth 41Ám, process length 16 Ám. Observed range, central body length (with operculum) 44Ám, central body length (without operculum) 28-42Ám, central body breadth 30-46Ám, process length 14-23Ám.
Discussion: Bujak 1976, p. 107
The process platforms on A. fenestratum are composed of interconnecting trabeculae which form either loose networks, or perforate membranes with openings of regular or irregular size and shape. Smaller, regular fenestrations are often concentrated along the platform margins, and larger, irregular fenestrations near the process stems. Adjacent process platforms are sometimes joined by trabeculae, particularly those near the antapex. The process platforms also vary in shape and may have either entire or ragged margins. The resemblance of the process platforms on A. fenestratum to those on A. diktyoplokus give the two species a similar appearance, but detailed comparison of the overall morphology of these species indicates a number of differences. A. diktyoplokus has a spherical to subspherical central body which is not flattened dorsoventrally, whereas the central body of A. fenestratum is typically flattened dorsoventrally with subcircular to subquadrate outline. The process platforms on specimens of A. diktyoplokus from the Barton Beds have entire margins and regularly ordered fenestrations. Only a few specimens of A. fenestratum from the Middle and Upper Barton Beds possess similar platforms, and the earliest representatives of A. fenestratum from the Lower Barton Beds, invariably have L platforms with ragged margins and irregular fenestrations (Plate II, 9). On A. diktyoplokus the processes reflect a tabulation of 4',6",5-6"',0--lp,1"", with one or two extremely slender cingular processes rarely present on the cingular zone. On A. fenestratum, processes are always present on the lateral margins of the cingular zone and on the posterior intercalary plate area, with additional processes often present between the posterior intercalary and antapical processes. Unlike A. diktyoplokus, A. fenestratum never has processes on plate areas 6 and 6" ' . The mean dimensions of central body and overall length and breadth are distinctly smaller for A. fenestratum than forA. diktyoplokus. A. multicornutum lacks the distinctiveprocess platforms which characterize A. fenestratum, but is identical in all other morphological details. Both have dorsoventrally flattened central bodies of similar outline and a sulcal notch offset to the left on the ventral surface. The processes on both species are solid, finely fibrous and reflect a tabulation of 4',5" ,xc,5"',lp,1"", with additional processes often present between the posterior intercalary and antapical processes. Accessory archeopyle sutures indicate the presence of a sixth precingular and an anterior sulcal plate area, although they do not bear processes. The mean dimensions of both species are closely comparable and the process platforms on A. fenestratum often include bifurcate process extremities identical to those on A. multicornutum (Plate II, 10). These morphological similarities are discussed further on p. 114, in the context of a possible evolutionary relationship between A. multicornutum and A. fenestratum. A. fenestratum appears in the highest horizons of the Lower Barton Beds at Barton and Alum Bay. At Whitecliff Bay, these horizons are not exposed. In all three sections, A. fenestratum consistently occurs in samples of marine sediments from the Middle and Upper Barton Beds.
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Emended description: Stover and Williams, 1995, p. 110-111
Shape: Cysts skolochorate, bodies subspherical and may be slightly flattened dorso-ventrally.
Wall relationships: Autophragm only.
Wall features: Autophragm scabrate to granular and bears 21 to 23 intratabular processes, 9 on epicysts, eight on hypocysts and four to six paracingular processes. Processes with solid, relatively narrow, rarely branched stems and reticulate clypeate tips whose margins may be irregularly ragged to subcircular or entire and polygonal. Some adjacent process tips may be connected by trabeculae. Outlines of process tips with entire margins simulate the shapes of reflected paraplates.
Excystment mode: Archeopyle apical; operculum tetratabular, simple, nearly equidimensional and free, with four processes.
Paratabulation: Gonyaulacoid, indicated by the archeopyle sutures plus the positions of the intratabular processes. Paraplate 6'' without a process and narrower than paraplate 1''. Processes on hypocyst arranged in partiform pattern; paraplate 6''' does not have a process. Process formula: 4', 5'', 4-6c, 5''', 1p, 2'''', 0s.
Paracingulum: Indicated by the presence of 4 to 6 processes with transversely elongate clypeate tips.
Parasulcus: Parasulcal processes absent although a frequently discernible parasulcal notch is offset
slightly.
Size: Specimens are 60 Ám to 95 Ám in diameter, including processes.
Comments:
Our interpretation of the hypocystal paratabulation in Enneadocysta fenestrata as partiform is based on the following:
a. The illustrations of the holotype (pl. 3, fig. 2) and paratypes (pl. 2, figs. 9-12; pl. 3, figs. 1, 3, 4) in
Bujak (1976).
b. The diagnosi and discussion in Bujak (1976)
c. Discussion with J.P. Bujak who has re-examined the type material.
In the diagnosis, Bujak (1976, p. 107) stated: "Reflected process tabulation 4', 5'', xc, 5''', 1p, 1''''; plate areas 6'', 6''', anterior sulcal area, and middorsal and midventral areas without processes. Elsewhere one process per plate area, except near antapex where additional processes sometimes present, and on lateral cingular margins where four to nine processes always present." Examination of the accompanying illustrations (e.g. Bujak 1976, pl. 2, figs. 11-12) clearly indicates two antapical processes in the orientation typical for Enneadocysta. Bujak (1976, p. 109) stated "... additional processes often present between the posterior intercalary and antapical processes." Further confirmation is provided by the offset sulcal notch.
Comparison:
Enneadocysta fenestrata is the only species of the genus with clypeate distal terminations to the processes. The other species with similar processes, Areosphaeridium diktyoplokus, does not have a slightly dorso-ventrally flattened body or four to six consistently present paracingular processes and lacks a process on the sixth precingular paraplate. More importantly, in Areosphaeridium diktyoplokus the hypocystal paratabulation is standard sexiform (textf1g. 1, nos. Al-A2).
Type locality and stratum:
Locality: southern England, Isle of Wight, Whitecliff Bay section.
Stratum: Middle Barton Beds (upper Middle Eocene, Bartonian), sample W-8 of Bujak (see Bujak et al. 1980), about 33 meters above the postulated Barton Beds - Bracklesham Beds boundary.
Holotype:
Specimen on slide W8a illustrated in Bujak (1976, pl. 3, fig. 2).
Stratigraphic and geographic data:
The geochronologic range of Enneadocysta fenestrata is late Mid Eocene (Bartonian) to early Late Eocene (Priabonian). In terms of depositional sequences, the species base is in the 42.5 Ma sequence and its top is near the base of the 39.5 Ma sequence. In terms of nannofossil zones it ranges from within NP 16 to the lower part of NP 18 which, in turn, correlates with planktonic foraminiferal zones P 12 to P 15. Powell (1992) showed an age range from about 42.2 Ma to 39.0 Ma.
Substantiated reports of geographic occurrences are from southern England, Hampshire Basin, Lower and Middle Barton Beds and Chama Beds. Additional but unsubstantiated records are listed in Appendix 2.
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originally Areosphaeridium, subsequently and now Enneadocysta
Holotype: Bujak 1976: Plate III, fig. 2
Locus typicus: Whitecliff Bay, Isle of Wight, England.
Stratum typicum: Middle Barton Beds (Upper Eocene)
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Enneadocysta fenestrata (Bujak, 1976) Stover and Williams, 1995, emend. Stover and Williams, 1995. Autophragm scabrate to granular with 21 to 23 processes, 9 on the epicyst, eight on the hypocyst, and four to six paracingulars. Processes with solid, relatively narrow stems, and reticulate, clypeate tips, whose margins may be irregularly ragged to subcircular or entire and polygonal. Some adjacent processes may be connected by trabeculae. Outline of process tips with entire margins may simulate the shape of the plates. Process formula: 4', 5" (no process on plate 6"), 4-6c, 5"’, 1p, 2"”. Size: central body length (without operculum) 44 µm, width 30-46 µm, process length 14-23 µm.
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Original diagnosis: Bujak 1976, p. 107: Areosphaeridium fenestratum
Central body dorsoventrally compressed, outline subcircular to subquadrate. Autophragm scabrate to granulate, forming intratabular processes with solid, fibrous stems. Processes distally bifurcate or branched, bearing platforms formed of interconnecting trabeculae. Platforms of adjacent processes sometimes connected by trabeculae. Reflected process tabulation 4',5",xc,5"',1p,1""; plate areas 6 , 6"', anterior sulcal area, and mid-dorsal and mid-ventral areas without processes. Elsewhere one process per plate area, except near antapex where additional processes sometimes present, and on lateral cingular margins where four to nine processes always present. Archeopyle apical, tetratabular. Operculum simple and usually detached. Short accessory archeopyle sutures often partially defining six precingular plate areas, and an anterior sulcal plate area offset to the left on the ventral surface.
Dimensions: Holotype, central body length (without operculum) 33Ám, central body breadth 41Ám, process length 16 Ám. Observed range, central body length (with operculum) 44Ám, central body length (without operculum) 28-42Ám, central body breadth 30-46Ám, process length 14-23Ám.
Discussion: Bujak 1976, p. 107
The process platforms on A. fenestratum are composed of interconnecting trabeculae which form either loose networks, or perforate membranes with openings of regular or irregular size and shape. Smaller, regular fenestrations are often concentrated along the platform margins, and larger, irregular fenestrations near the process stems. Adjacent process platforms are sometimes joined by trabeculae, particularly those near the antapex. The process platforms also vary in shape and may have either entire or ragged margins. The resemblance of the process platforms on A. fenestratum to those on A. diktyoplokus give the two species a similar appearance, but detailed comparison of the overall morphology of these species indicates a number of differences. A. diktyoplokus has a spherical to subspherical central body which is not flattened dorsoventrally, whereas the central body of A. fenestratum is typically flattened dorsoventrally with subcircular to subquadrate outline. The process platforms on specimens of A. diktyoplokus from the Barton Beds have entire margins and regularly ordered fenestrations. Only a few specimens of A. fenestratum from the Middle and Upper Barton Beds possess similar platforms, and the earliest representatives of A. fenestratum from the Lower Barton Beds, invariably have L platforms with ragged margins and irregular fenestrations (Plate II, 9). On A. diktyoplokus the processes reflect a tabulation of 4',6",5-6"',0--lp,1"", with one or two extremely slender cingular processes rarely present on the cingular zone. On A. fenestratum, processes are always present on the lateral margins of the cingular zone and on the posterior intercalary plate area, with additional processes often present between the posterior intercalary and antapical processes. Unlike A. diktyoplokus, A. fenestratum never has processes on plate areas 6 and 6" ' . The mean dimensions of central body and overall length and breadth are distinctly smaller for A. fenestratum than forA. diktyoplokus. A. multicornutum lacks the distinctiveprocess platforms which characterize A. fenestratum, but is identical in all other morphological details. Both have dorsoventrally flattened central bodies of similar outline and a sulcal notch offset to the left on the ventral surface. The processes on both species are solid, finely fibrous and reflect a tabulation of 4',5" ,xc,5"',lp,1"", with additional processes often present between the posterior intercalary and antapical processes. Accessory archeopyle sutures indicate the presence of a sixth precingular and an anterior sulcal plate area, although they do not bear processes. The mean dimensions of both species are closely comparable and the process platforms on A. fenestratum often include bifurcate process extremities identical to those on A. multicornutum (Plate II, 10). These morphological similarities are discussed further on p. 114, in the context of a possible evolutionary relationship between A. multicornutum and A. fenestratum. A. fenestratum appears in the highest horizons of the Lower Barton Beds at Barton and Alum Bay. At Whitecliff Bay, these horizons are not exposed. In all three sections, A. fenestratum consistently occurs in samples of marine sediments from the Middle and Upper Barton Beds.
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Emended description: Stover and Williams, 1995, p. 110-111
Shape: Cysts skolochorate, bodies subspherical and may be slightly flattened dorso-ventrally.
Wall relationships: Autophragm only.
Wall features: Autophragm scabrate to granular and bears 21 to 23 intratabular processes, 9 on epicysts, eight on hypocysts and four to six paracingular processes. Processes with solid, relatively narrow, rarely branched stems and reticulate clypeate tips whose margins may be irregularly ragged to subcircular or entire and polygonal. Some adjacent process tips may be connected by trabeculae. Outlines of process tips with entire margins simulate the shapes of reflected paraplates.
Excystment mode: Archeopyle apical; operculum tetratabular, simple, nearly equidimensional and free, with four processes.
Paratabulation: Gonyaulacoid, indicated by the archeopyle sutures plus the positions of the intratabular processes. Paraplate 6'' without a process and narrower than paraplate 1''. Processes on hypocyst arranged in partiform pattern; paraplate 6''' does not have a process. Process formula: 4', 5'', 4-6c, 5''', 1p, 2'''', 0s.
Paracingulum: Indicated by the presence of 4 to 6 processes with transversely elongate clypeate tips.
Parasulcus: Parasulcal processes absent although a frequently discernible parasulcal notch is offset
slightly.
Size: Specimens are 60 Ám to 95 Ám in diameter, including processes.
Comments:
Our interpretation of the hypocystal paratabulation in Enneadocysta fenestrata as partiform is based on the following:
a. The illustrations of the holotype (pl. 3, fig. 2) and paratypes (pl. 2, figs. 9-12; pl. 3, figs. 1, 3, 4) in
Bujak (1976).
b. The diagnosi and discussion in Bujak (1976)
c. Discussion with J.P. Bujak who has re-examined the type material.
In the diagnosis, Bujak (1976, p. 107) stated: "Reflected process tabulation 4', 5'', xc, 5''', 1p, 1''''; plate areas 6'', 6''', anterior sulcal area, and middorsal and midventral areas without processes. Elsewhere one process per plate area, except near antapex where additional processes sometimes present, and on lateral cingular margins where four to nine processes always present." Examination of the accompanying illustrations (e.g. Bujak 1976, pl. 2, figs. 11-12) clearly indicates two antapical processes in the orientation typical for Enneadocysta. Bujak (1976, p. 109) stated "... additional processes often present between the posterior intercalary and antapical processes." Further confirmation is provided by the offset sulcal notch.
Comparison:
Enneadocysta fenestrata is the only species of the genus with clypeate distal terminations to the processes. The other species with similar processes, Areosphaeridium diktyoplokus, does not have a slightly dorso-ventrally flattened body or four to six consistently present paracingular processes and lacks a process on the sixth precingular paraplate. More importantly, in Areosphaeridium diktyoplokus the hypocystal paratabulation is standard sexiform (textf1g. 1, nos. Al-A2).
Type locality and stratum:
Locality: southern England, Isle of Wight, Whitecliff Bay section.
Stratum: Middle Barton Beds (upper Middle Eocene, Bartonian), sample W-8 of Bujak (see Bujak et al. 1980), about 33 meters above the postulated Barton Beds - Bracklesham Beds boundary.
Holotype:
Specimen on slide W8a illustrated in Bujak (1976, pl. 3, fig. 2).
Stratigraphic and geographic data:
The geochronologic range of Enneadocysta fenestrata is late Mid Eocene (Bartonian) to early Late Eocene (Priabonian). In terms of depositional sequences, the species base is in the 42.5 Ma sequence and its top is near the base of the 39.5 Ma sequence. In terms of nannofossil zones it ranges from within NP 16 to the lower part of NP 18 which, in turn, correlates with planktonic foraminiferal zones P 12 to P 15. Powell (1992) showed an age range from about 42.2 Ma to 39.0 Ma.
Substantiated reports of geographic occurrences are from southern England, Hampshire Basin, Lower and Middle Barton Beds and Chama Beds. Additional but unsubstantiated records are listed in Appendix 2.
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