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Enneadocysta multicornuta
Enneadocysta multicornuta (Eaton, 1971) emend. Stover and Williams, 1995
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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 multicornuta (Eaton, 1971) Stover and Williams, 1995, emend. Stover and Williams, 1995, has 24 processes, nine on the epicyst, nine on the hypocyst and six cingular. Process tips usually licrate. Tips of paracingular processes branched. Process formula: 4', 5" (none on 6" or as), 6c, 6"’, 2"”, 1ps. Size: body diameter 34-50 µm, overall 63-100 µm, process length 11-32 µm, most processes are in the range 18-25 µm.
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Eaton, 1971, p. 363-364
Original diagnosis: The central body has a sub-circular to sub-quadrate outline and a finely granular surface. The processes are intratabular and have solid fibrous stems of variable length and breadth. Each process is distally expanded and bifurcate; the attitude of the bifurcations varies from patulate to recurved. The bifurcations are of variable length, and they vary in breadth from slender with a denticulate distal margin, to broad, typically net-like, with an irregular distal margin. Fenestration is sometimes present in a few of the process stems and produces stem branches. The tabulation of 4', 6", 6''', 1p, 1'''' is not fully reflected by the Intratabular processes. On the apical zonethere are 4 processes (1' - 4'). On the precingular zone there are five processes (1" - 5"), and plate 6" is devoid of processes. There are between four and seven cingular processes which are situated on the lateral margins of the cingular zone. On the postcingular zone there are five processes (1'''- 5'''), and plate 6''' is devoid of processes. There is one process reflecting the posterior intercalary plate (1p). The antapex is typically offset to the right of the mid-ventral line and bears one process (1''''). Between the postcingular processes and the antapical process there are between one and five additional processes. The archaeopyle is apical, tetratabular.
Dimensions - Holotype: central body (without operculum), length 46 Ám, breadth 50 Ám; processes, length 16.5-22 Ám, breadth 1-3 Ám. Observed range: central body, length (without operculum) 34-47 Ám, breadth 34-50 Ám; processes, length 11-25 Ám, breadth 1-6 Ám; number of specimens measured, 20.
Discussion: Eaton, 1971, p. 364
The variation in the form of the processes in A. multicornutum is similar to that shown by A. arcuatum, including the frequent occurrence of broader processes reflecting plates 2''' and 4''' (pl. 4 fig. 2). The cingular processes in A. multicornutum are typically slender. Although they are restricted to the margins of the cingular zone, the cingular processes are not randomly distributed, but are arranged in a line approximately parallel to the pre- and postcingular zones. As with A. arcuatum the additional processes are probably postcingular or antapical rather than reflecting distinct plate areas. The number of cingular and additional processes quoted in the diagnosis for A. multicornutum is based on specimens from the Bracklesham Beds; specimens with a greater number of processes may occur.
Affinities:
Eaton, 1971, p. 364: A. multicornutum is distinguished from A. arcuatum var. A by having cingular processes and frequently having a greater number of additional processes on the hypotract. A. multicornutum differs from A. arcuatum var. B, in having plates 6" and 6''' devoid of processes, and in always having cingular processes.
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Stover and Williams, 1995, p. 112-113
Plate 4, figures 1a-b, 2a-b, 3a-b; text-figure 1, no. D, I
Areosphaeridium multicornutum Eaton 1971, p. 363-364, pl. 4, figs. 1-7; text-fig. 6.
Emended description:
Shape: Cysts skolochorate with subspherical central body.
Wall relationships: Autophragm only.
Wall features: Autophragm smooth or faintly granular. Central body typically bears 24 intratabular processes, nine on epicyst, nine on hypocyst and six paracingular processes. Process stems solid, smooth or very faintly fibroid, usually narrow and expanded distally, generally abruptly; process tips mostly licrate, less commonly vasiform or branched. On processes with licrate tips, terminations are arcuate, relatively short, with smooth inner margins and denticulate to spinulate outer margins. Tips of all precingular processes may be licrate or those on ventral processes may be branched. On processes with licrate tips, ends of arcuations are directed equatorially. Stems of the six paracingular processes invariably narrower than those of other processes; tips of paracingular processes branched and may be finely reticulate distally. With the exception of the posterior parasulcal process, which may be branched distally, process tips of hypocystal processes are licrate. Ends of those on postcingular processes also face equatorially. Thus, ends of arcuations on opposing precingular and postcingular processes with licrate tips face each other. Processes on paraplates 1''' and 6''' similar in size to those on paraplates 1'''' and 2''''. Ends of opposing licrate structures on the antapical processes usually face each other medially, although this orientation is not clearly evident on all specimens.
Excystmenl type: Archeopyle apical; operculum tetratabular, simple, approximately equidimensional and free.
Paratabulalion: Indicated on epicyst by principal archeopyle suture and, when present, short accessory sutures, and by positions of intratabular processes; paratabulation expressed elsewhere on central body solely by process positions. Process formula: 4', 5'', 6c, 6''', 2'''', 1ps. Five precingular processes present; none on paraplates 6'' or anterior sulcal. Two hypocystal processes arranged in partiform configuration.
Paracingulum: Indicated by the presence of six paracingular processes.
Parasulcus: Limits marked anteriorly by sulcal notch and posteriorly by posterior parasulcal process.
Size: Intermediate; measurement of 32 specimens, including some measurements given in Eaton (1971) and those of the specimens illustrated in Bujak (1976): body diameter 34 Ám (44 Ám) 50 Ám, overall diameter 63 Ám (83 Ám) 100 Ám, process lengths 11 to 32 Ám, most processes are in the 18 Ám to 25 Ám range. Mean values shown in parentheses.
Comments
Sarjeant (1984) regarded Enneadocysta (as Areosphaeridium) multicornuta as a taxonomic junior synonym of Areosphaeridium [now Enneadocysta] pectiniforme. Enneadocysta multicornuta does not have processes on the sixth precingular paraplate or the anterior sulcal paraplate (pl. 4, fig. 1a), whereas Enneadocysta pectiniformis has a single process on both the sixth precingular and the anterior sulcal.
Type locality and stratum:
Locality: southern England, Isle of Wight, Alum Bay section.
Stratum: Bracklesham Beds (lower Middle Eocene, Lutetian), sample AB-44 at the top of Bed 19 of Eaton (1976) and immediately below the Bracklesham Beds - Barton Beds boundary.
Stratigraphic and geographic data:
The confirmed range of Enneadocysta multicornuta is from the latest part of the early Mid Eocene (Lutetian) to Late Eocene (Priabonian). In terms of depositional sequences, the base of Enneadocysta multicornuta lies in the 42.5 Ma sequence and its top is in the 37 Ma sequence. In terms of nannoplankton zones the species ranges from Zone NP 16 to Zone NP 20, which, in turn, correlates with the upper part of planktonic foraminiferal Zone P 12 to Zone P 17.
The stratigraphic range of this species - as depicted by Williams (1975), Williams and Brideaux (1975), Williams and Bujak ( l 977b) - is Early Eocene to Mid/Late Oligocene. We believe the Mid Eocene to Late Eocene record given in Williams and Bujak (1985) is more reliable.
Confirmed geographic occurrences of Enneadocysta multicornuta are limited and confined to the Northern Hemisphere; the species has been reported from England, Italy, the Grand Banks of offshore eastern Canada and China. Post-Eocene records of Enneadocysta multicornuta require substantiation.
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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 multicornuta (Eaton, 1971) Stover and Williams, 1995, emend. Stover and Williams, 1995, has 24 processes, nine on the epicyst, nine on the hypocyst and six cingular. Process tips usually licrate. Tips of paracingular processes branched. Process formula: 4', 5" (none on 6" or as), 6c, 6"’, 2"”, 1ps. Size: body diameter 34-50 µm, overall 63-100 µm, process length 11-32 µm, most processes are in the range 18-25 µm.
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Eaton, 1971, p. 363-364
Original diagnosis: The central body has a sub-circular to sub-quadrate outline and a finely granular surface. The processes are intratabular and have solid fibrous stems of variable length and breadth. Each process is distally expanded and bifurcate; the attitude of the bifurcations varies from patulate to recurved. The bifurcations are of variable length, and they vary in breadth from slender with a denticulate distal margin, to broad, typically net-like, with an irregular distal margin. Fenestration is sometimes present in a few of the process stems and produces stem branches. The tabulation of 4', 6", 6''', 1p, 1'''' is not fully reflected by the Intratabular processes. On the apical zonethere are 4 processes (1' - 4'). On the precingular zone there are five processes (1" - 5"), and plate 6" is devoid of processes. There are between four and seven cingular processes which are situated on the lateral margins of the cingular zone. On the postcingular zone there are five processes (1'''- 5'''), and plate 6''' is devoid of processes. There is one process reflecting the posterior intercalary plate (1p). The antapex is typically offset to the right of the mid-ventral line and bears one process (1''''). Between the postcingular processes and the antapical process there are between one and five additional processes. The archaeopyle is apical, tetratabular.
Dimensions - Holotype: central body (without operculum), length 46 Ám, breadth 50 Ám; processes, length 16.5-22 Ám, breadth 1-3 Ám. Observed range: central body, length (without operculum) 34-47 Ám, breadth 34-50 Ám; processes, length 11-25 Ám, breadth 1-6 Ám; number of specimens measured, 20.
Discussion: Eaton, 1971, p. 364
The variation in the form of the processes in A. multicornutum is similar to that shown by A. arcuatum, including the frequent occurrence of broader processes reflecting plates 2''' and 4''' (pl. 4 fig. 2). The cingular processes in A. multicornutum are typically slender. Although they are restricted to the margins of the cingular zone, the cingular processes are not randomly distributed, but are arranged in a line approximately parallel to the pre- and postcingular zones. As with A. arcuatum the additional processes are probably postcingular or antapical rather than reflecting distinct plate areas. The number of cingular and additional processes quoted in the diagnosis for A. multicornutum is based on specimens from the Bracklesham Beds; specimens with a greater number of processes may occur.
Affinities:
Eaton, 1971, p. 364: A. multicornutum is distinguished from A. arcuatum var. A by having cingular processes and frequently having a greater number of additional processes on the hypotract. A. multicornutum differs from A. arcuatum var. B, in having plates 6" and 6''' devoid of processes, and in always having cingular processes.
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Stover and Williams, 1995, p. 112-113
Plate 4, figures 1a-b, 2a-b, 3a-b; text-figure 1, no. D, I
Areosphaeridium multicornutum Eaton 1971, p. 363-364, pl. 4, figs. 1-7; text-fig. 6.
Emended description:
Shape: Cysts skolochorate with subspherical central body.
Wall relationships: Autophragm only.
Wall features: Autophragm smooth or faintly granular. Central body typically bears 24 intratabular processes, nine on epicyst, nine on hypocyst and six paracingular processes. Process stems solid, smooth or very faintly fibroid, usually narrow and expanded distally, generally abruptly; process tips mostly licrate, less commonly vasiform or branched. On processes with licrate tips, terminations are arcuate, relatively short, with smooth inner margins and denticulate to spinulate outer margins. Tips of all precingular processes may be licrate or those on ventral processes may be branched. On processes with licrate tips, ends of arcuations are directed equatorially. Stems of the six paracingular processes invariably narrower than those of other processes; tips of paracingular processes branched and may be finely reticulate distally. With the exception of the posterior parasulcal process, which may be branched distally, process tips of hypocystal processes are licrate. Ends of those on postcingular processes also face equatorially. Thus, ends of arcuations on opposing precingular and postcingular processes with licrate tips face each other. Processes on paraplates 1''' and 6''' similar in size to those on paraplates 1'''' and 2''''. Ends of opposing licrate structures on the antapical processes usually face each other medially, although this orientation is not clearly evident on all specimens.
Excystmenl type: Archeopyle apical; operculum tetratabular, simple, approximately equidimensional and free.
Paratabulalion: Indicated on epicyst by principal archeopyle suture and, when present, short accessory sutures, and by positions of intratabular processes; paratabulation expressed elsewhere on central body solely by process positions. Process formula: 4', 5'', 6c, 6''', 2'''', 1ps. Five precingular processes present; none on paraplates 6'' or anterior sulcal. Two hypocystal processes arranged in partiform configuration.
Paracingulum: Indicated by the presence of six paracingular processes.
Parasulcus: Limits marked anteriorly by sulcal notch and posteriorly by posterior parasulcal process.
Size: Intermediate; measurement of 32 specimens, including some measurements given in Eaton (1971) and those of the specimens illustrated in Bujak (1976): body diameter 34 Ám (44 Ám) 50 Ám, overall diameter 63 Ám (83 Ám) 100 Ám, process lengths 11 to 32 Ám, most processes are in the 18 Ám to 25 Ám range. Mean values shown in parentheses.
Comments
Sarjeant (1984) regarded Enneadocysta (as Areosphaeridium) multicornuta as a taxonomic junior synonym of Areosphaeridium [now Enneadocysta] pectiniforme. Enneadocysta multicornuta does not have processes on the sixth precingular paraplate or the anterior sulcal paraplate (pl. 4, fig. 1a), whereas Enneadocysta pectiniformis has a single process on both the sixth precingular and the anterior sulcal.
Type locality and stratum:
Locality: southern England, Isle of Wight, Alum Bay section.
Stratum: Bracklesham Beds (lower Middle Eocene, Lutetian), sample AB-44 at the top of Bed 19 of Eaton (1976) and immediately below the Bracklesham Beds - Barton Beds boundary.
Stratigraphic and geographic data:
The confirmed range of Enneadocysta multicornuta is from the latest part of the early Mid Eocene (Lutetian) to Late Eocene (Priabonian). In terms of depositional sequences, the base of Enneadocysta multicornuta lies in the 42.5 Ma sequence and its top is in the 37 Ma sequence. In terms of nannoplankton zones the species ranges from Zone NP 16 to Zone NP 20, which, in turn, correlates with the upper part of planktonic foraminiferal Zone P 12 to Zone P 17.
The stratigraphic range of this species - as depicted by Williams (1975), Williams and Brideaux (1975), Williams and Bujak ( l 977b) - is Early Eocene to Mid/Late Oligocene. We believe the Mid Eocene to Late Eocene record given in Williams and Bujak (1985) is more reliable.
Confirmed geographic occurrences of Enneadocysta multicornuta are limited and confined to the Northern Hemisphere; the species has been reported from England, Italy, the Grand Banks of offshore eastern Canada and China. Post-Eocene records of Enneadocysta multicornuta require substantiation.
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