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Enneadocysta magna
Enneadocysta magna Fensome et al., 2007, p.394–396, pl.1, figs.1–20, pl.2. figs.1–19; text-figs.5A,B,6A–E.
Holotype: Fensome et al., 2007, pl.1, figs.5–7.
Age: Rupelian.
Original description (Fensome et al., ,2007):
Enneadocysta magna Fensome, Guerstein and Williams, n. sp. Plate 1, figures 1-20; Plate 2, figures 1-19 ; text-figures 5 A-B, 6 A-E
Derivation of name: From the Latin magnus, large or great, in reference to the large size of cysts of this species relative to other species of the genus.
Diagnosis: A species of Enneadocysta with large cysts (typically 60-70µm wide and 45-50µm long, excluding operculum) and generally slender licrate processes that are commonly highly asymmetrical distally, but may also be nearly symmetrical; there are four precingular processes, and cingular processes sometimes reduced to knob-like projections.
Description. Shape: Cyst chorate with a lenticular central body, dorso-ventrally compressed and with an offset sulcal notch. Antapical outline generally asymmetrical, usually more pronounced on the left side. Wall relationships: Autophragm only. Wall features: In cross-section, autophragm surface is slightly rough (scabrate); in plain view the autophragm appears irregularly granulate to pitted, though this may be structural (within the wall) rather than surficial. Central body with 19 to 22 processes: 8 on the epicyst, 9 or 10 on the hypocyst, and 1 to 4 on the cingulum. Processes usually mesotabular to commonly obtabular, in the latter case generally migrating ambitally toward plate boundaries (pl. 1, figs.17-19; text-figure 6). Process stems smooth, solid to perforate, mostly cylindrical, generally narrow and long (but see specific comments about postcingulars below). Processes may be branched anywhere along their length, and occasionally so deeply that two (rarely more) slender processes result; especially in cases where processes are basally split, but not exclusively so, weakly developed arcuate ridges may connect process bases. Most processes show usually strongly asymmetrical branching or expansion distally. Process tips may be licrate, simply or complexly branched or acuminate. Licrate tips may be strongly asymmetrical with a single branch, or they may be V- to horseshoe-shaped, with smooth inner margins and weakly to moderately denticulate outer margins. The two dorsal apical processes (2' and 3') are larger and more complex than the ventral two. The four precingular processes (1'', 2'', 4', 5') are more or less equal in size and located toward the ambitus. The cingular processes may be expressed as rounded protuberances or fully developed with branched or licrate terminations. The processes on plates 2''' and 5''' may be wider than the other four postcingular processes. The 3''' process is generally extremely slender. Process 6''' is closely adjacent to the 5''' process. The two antapical processes are laterally located, of equal size, and their licrate tips face each other. The posterior sulcal process is wider than the 1''' process and is usually branched. Archeopyle: Apical, type (tA); operculum tetratabular, simple, free and generally longer from left to right than dorso-ventrally (text-figure 6 C). Tabulation: Expressed on epicyst by archeopyle sutures and by location of processes, which tend to be obtabular rather than mesotabular. Plates 3'' and 6'' never have processes. Cingulum indicated by the presence of one to four processes: we consider that the two cingular plates consistently devoid of processes are 3c and 4c. Processes are generally present on 2c and 5c and also commonly on 1c and 6c. On 2c and 5c the processes appear to have migrated towards the ambitus. All the postcingular plates have processes, and these show a strong tendency to be obtabular. A single antapical plate is indicated by the position of two lateral processes which appear to be penitabular. The position of the sulcus is indicated anteriorly by offset sulcal notch (text-figures 5 A, 6 A, D) and evidently posteriorly by a single, commonly branched process. The posterior intercalary plate appears to be free of processes. (We consistently observed only one plate on the 1p-ps area. As this process is always located directly below the sulcal notch, and considering that it could be obtabular, we consider that it represents the ps plate rather than the 1p plate.) Process formula thus generally: 4', 4'', 1-4c, 6''', 1ps, 2''''.
Dimensions: Range of 12 specimens except where noted: central body width 59 (68) 73µm; length (excluding operculum) 41 (55) 63µm; maximum diameter of operculum 38µm (one specimen); process length up to 31 (43) 58µm; maximum process length as percentage of central body width on individual specimen 48 (63) 87 percent.
Holotype: Pl. 1, figs. 5-7. Location: sample P1435, slide 10, co-ordinates 14.7 x 100.5, England Finder O43/4. Repository: GSC type collection no. 128905. Dimensions: central body width 70µm, central body length (without operculum) 57µm, processes up to 44µm long. Geographic occurrence: Corehole 16, Geological Survey of Canada (Atlantic) locality no. D52, Jeanne d’Arc Basin, Grand Banks of Newfoundland, offshore eastern Canada, sample depth 88.1-91.1 m (289-299 feet; composite sample from conventional core).
Age: Oligocene (Rupelian) based on dinocyst ranges.
Occurrence: Oligocene, here interpreted as Rupelian in Corehole 16 – samples P1435 at 88.1 m (289 feet) and P1436 at 116.4 m (382 feet). The species has also be recorded from several wells on the Grand Banks of Newfoundland, including Hibernia B-08, from which the penitabular nature of the antapical processes was first recognized (pl. 1, figs. 4,8).
Comparison: The other species of Enneadocysta with less than 6 precingular processes are Enneadocysta arcuata, Enneadocysta fenestrata and Enneadocysta multicornuta, all of which have five. Enneadocysta dictyostila rarely has only five precingular processes but more commonly has six. Two other diagnostic characteristics of Enneadocysta magna are the large size and the slender licrate processes with highly asymmetrical distal extremities. Licracysta? semicirculata appears similar in overall morphology but has more than one process per plate.
Holotype: Fensome et al., 2007, pl.1, figs.5–7.
Age: Rupelian.
Original description (Fensome et al., ,2007):
Enneadocysta magna Fensome, Guerstein and Williams, n. sp. Plate 1, figures 1-20; Plate 2, figures 1-19 ; text-figures 5 A-B, 6 A-E
Derivation of name: From the Latin magnus, large or great, in reference to the large size of cysts of this species relative to other species of the genus.
Diagnosis: A species of Enneadocysta with large cysts (typically 60-70µm wide and 45-50µm long, excluding operculum) and generally slender licrate processes that are commonly highly asymmetrical distally, but may also be nearly symmetrical; there are four precingular processes, and cingular processes sometimes reduced to knob-like projections.
Description. Shape: Cyst chorate with a lenticular central body, dorso-ventrally compressed and with an offset sulcal notch. Antapical outline generally asymmetrical, usually more pronounced on the left side. Wall relationships: Autophragm only. Wall features: In cross-section, autophragm surface is slightly rough (scabrate); in plain view the autophragm appears irregularly granulate to pitted, though this may be structural (within the wall) rather than surficial. Central body with 19 to 22 processes: 8 on the epicyst, 9 or 10 on the hypocyst, and 1 to 4 on the cingulum. Processes usually mesotabular to commonly obtabular, in the latter case generally migrating ambitally toward plate boundaries (pl. 1, figs.17-19; text-figure 6). Process stems smooth, solid to perforate, mostly cylindrical, generally narrow and long (but see specific comments about postcingulars below). Processes may be branched anywhere along their length, and occasionally so deeply that two (rarely more) slender processes result; especially in cases where processes are basally split, but not exclusively so, weakly developed arcuate ridges may connect process bases. Most processes show usually strongly asymmetrical branching or expansion distally. Process tips may be licrate, simply or complexly branched or acuminate. Licrate tips may be strongly asymmetrical with a single branch, or they may be V- to horseshoe-shaped, with smooth inner margins and weakly to moderately denticulate outer margins. The two dorsal apical processes (2' and 3') are larger and more complex than the ventral two. The four precingular processes (1'', 2'', 4', 5') are more or less equal in size and located toward the ambitus. The cingular processes may be expressed as rounded protuberances or fully developed with branched or licrate terminations. The processes on plates 2''' and 5''' may be wider than the other four postcingular processes. The 3''' process is generally extremely slender. Process 6''' is closely adjacent to the 5''' process. The two antapical processes are laterally located, of equal size, and their licrate tips face each other. The posterior sulcal process is wider than the 1''' process and is usually branched. Archeopyle: Apical, type (tA); operculum tetratabular, simple, free and generally longer from left to right than dorso-ventrally (text-figure 6 C). Tabulation: Expressed on epicyst by archeopyle sutures and by location of processes, which tend to be obtabular rather than mesotabular. Plates 3'' and 6'' never have processes. Cingulum indicated by the presence of one to four processes: we consider that the two cingular plates consistently devoid of processes are 3c and 4c. Processes are generally present on 2c and 5c and also commonly on 1c and 6c. On 2c and 5c the processes appear to have migrated towards the ambitus. All the postcingular plates have processes, and these show a strong tendency to be obtabular. A single antapical plate is indicated by the position of two lateral processes which appear to be penitabular. The position of the sulcus is indicated anteriorly by offset sulcal notch (text-figures 5 A, 6 A, D) and evidently posteriorly by a single, commonly branched process. The posterior intercalary plate appears to be free of processes. (We consistently observed only one plate on the 1p-ps area. As this process is always located directly below the sulcal notch, and considering that it could be obtabular, we consider that it represents the ps plate rather than the 1p plate.) Process formula thus generally: 4', 4'', 1-4c, 6''', 1ps, 2''''.
Dimensions: Range of 12 specimens except where noted: central body width 59 (68) 73µm; length (excluding operculum) 41 (55) 63µm; maximum diameter of operculum 38µm (one specimen); process length up to 31 (43) 58µm; maximum process length as percentage of central body width on individual specimen 48 (63) 87 percent.
Holotype: Pl. 1, figs. 5-7. Location: sample P1435, slide 10, co-ordinates 14.7 x 100.5, England Finder O43/4. Repository: GSC type collection no. 128905. Dimensions: central body width 70µm, central body length (without operculum) 57µm, processes up to 44µm long. Geographic occurrence: Corehole 16, Geological Survey of Canada (Atlantic) locality no. D52, Jeanne d’Arc Basin, Grand Banks of Newfoundland, offshore eastern Canada, sample depth 88.1-91.1 m (289-299 feet; composite sample from conventional core).
Age: Oligocene (Rupelian) based on dinocyst ranges.
Occurrence: Oligocene, here interpreted as Rupelian in Corehole 16 – samples P1435 at 88.1 m (289 feet) and P1436 at 116.4 m (382 feet). The species has also be recorded from several wells on the Grand Banks of Newfoundland, including Hibernia B-08, from which the penitabular nature of the antapical processes was first recognized (pl. 1, figs. 4,8).
Comparison: The other species of Enneadocysta with less than 6 precingular processes are Enneadocysta arcuata, Enneadocysta fenestrata and Enneadocysta multicornuta, all of which have five. Enneadocysta dictyostila rarely has only five precingular processes but more commonly has six. Two other diagnostic characteristics of Enneadocysta magna are the large size and the slender licrate processes with highly asymmetrical distal extremities. Licracysta? semicirculata appears similar in overall morphology but has more than one process per plate.