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Cooksonidium capricornum
Cooksonidium capricornum, (Cookson and Eisenack, 1965); emend. Stover and Williams, 1995
Holotype: Cookson and Eisenack, 1965, pl. 15, fig.7
Locus typicus: Browns Creek Clays (outwash section), Aire District, Victoria, Australia.
Stratum typicum: Upper Eocene (Priabonian) carbonaceous clay about 13.1 m above the Notostrea Greensand, Browns Creek Clays
Stratigraphic age and occurrence: Late Eocene; reported only from the type locality.
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Original description as Cordosphaeridium capricornum: [Cookson and Eisenack 1965, p. 128-129]:
Description:
Shell approximately spherical with numerous radially arranged appendages of characteristic form which vary in number in individual specimens and in size, form, and structure in one and the same specimen. All are solid; sorne are simple with unbranched or slightly branched apices or with terminal bifurcations which extend laterally and are upwardly or downwardly curved; others are broadly flattened and perforated to varying degrees with broad apices which narrow gradually as they curve backwards towards the shell. The upper surface of the apices and their extensions are consistently finely denticulate (Pl. 15, fig. 8, 9). The bases of the larger appendages are semicircular to, occasionally, almost circular, and similarly the tips of the apical prolongations sometimes appear to touch but, in reality, are never connected. The appendages are sometimes faintly and longitudinally striated; shorter and more pronounced striations may be evident at or near their points of origin. The surface of the shell is faintly granular.
The archeopyle is apical, the operculum bearing four appendages, two relatively large and two small (Pl. 15, fig. 9).
At the antapex an approximately circular area, outlined either completely (Pl. 15, fig. 6) or incompletely by a ridge to which a few small simple appendages may or may not be attached, has been seen. Such an area is suggestive of an antapical field.
Dimensions:
Holotype, overall width c. 78 µm, width of shell c. 52 µm.
Range, overall width c. 70-94 µm, width of shell c. 43-52 µm; appendages c. 18-30 µm long.
Affinities/Comment:
In the holotype the distribution of the appendages on the two surfaces differs. On the one shown in Pl. 15, fig. 7 there is a relatively large appendage-free area, whereas on the other surface the appendages are more evenly distributed. In the paratype (Pl. 15, fig. 2, 3) an almost circular antapical ridge supports a number of long thread-like appendages, the broadened apices of which unite to form an almost complete distal ring. At present the significance and constancy of such features cannot be estimated. C. capricornum is one of the most frequent forms in the greensand and higher deposits in the Browns Creek section.
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Emended description:
Stover and Williams, 1995, p. 107-108:
Description:
Shape: Cysts skolochorate with subspherical central body.
Wall relationships: Autophragm only.
Wall features: Autophragm finely granulate to pitted except on processes; central body with 16 to 18 intratabular single processes or process complexes, 10 or 11 on epicyst and six or seven on hypocyst, paracingular processes absent. On processes with single stems, the stems are solid, smooth or faintly fibroid, tapered distally and have slightly expanded bases. Distally they have licrate or flared tips and ends of the latter may be recurved. Process complexes composed of solid, faintly fibroid or smooth stems which extend from low, arcuate or heart-shaped proximal ridges. Usually two to four stems per arcuate process complex and up to eight stems on the antapical, generally cardioform, process complex. Stems in process complexes may be fenestrate and expanded proximally as well as distally. In each arcuate process complex the distal ends of stems are connected by a finely denticulate trabecula that commonly extends beyond the limits of the proximal ridge. In antapical complex a distal, usually complete denticulate trabeculum connects ends of stems. Trabeculae absent between process complexes or individual processes.
Excystment Type: Archeopyle apical; operculum tetratabular, simple, more or less equidimensional and free.
Paratabulation: Gonyaulacoid; expressed on epicyst by principal and accessory archeopyle sutures and by the locations of intratabular features, on hypocyst by positions of intratabular or penitabular structures only. Process formula 4', 6'', 0c, 5''', 0-1p, 1'''', 1as. Six precingular processes present subjacent to the archeopyle margin and an anterior parasulcal process may be present or absent. Structures on paraplates 3'' to 5'' frequently process complexes, less commonly individual processes; paraplates 2'' and 6'' may have single processes or process complexes; paraplates 1'' and the anterior sulcal have single processes. Paraplate 1'' is narrower than 6'' and the ends of arcuations of precingular processes with licrate tips are directed equatorially. Usually seven hypocystal processes: five postcingulars, one posterior intercalary and one antapical, arranged in the standard sexiform paratabulation pattern. Process on paraplate 1p may be missing. Paraplates 2''', 3''' and 4''' have process complexes, paraplate 5''' may have a single process or a process complex, paraplates 1''' and 1p have single processes and antapical paraplate has a roundly polygonal to heart-shaped process complex. Ends of the hypocystal dorsal process complexes generally point equatorially.
Paracingulum: Paracingular area devoid of processes.
Parasulcus: Usually a well-developed parasulcal notch with sometimes a single anterior sulcal process.
Dimensions:
Intermediate to large; measurements of 10 specimens: body diameter 50 µm (55 µm) 63 µm, overall diameter 75 µm (90 µm) 110 µm, process length 15 µm (23 µm) 32 µm, single process width 2.5 µm to 20 µm, most less than 8 µm wide at mid-length, process complex width 10 µm to 24 µm, most in the 16 µm to 20 µm range, width of single process tips 10 µm to 16 µm and width of process complex tips 30 µm to 40 µm. Mean values shown in parentheses.
Remarks:
Sarjeant (1981) regarded Cordosphaeridium capricornum as conspecific with and taxonomically junior to Areosphaeridium dictyostilum. His list of synonyms and other citations for Areosphaeridium dictyostilum includes the following entry: "1965a Cordosphaeridium capricornum Cookson and Eisenack, p. 128-129, pl. 15, figs. 1, ?2, 7-9." This citation excludes Cookson and Eisenack's figure 3, which is a different focus level of the specimen they showed as figure 2 but presented upside down, as well as figures 4-6. Sarjeant provided no definitive information about the dispositions of the figured specimens not included in the above quotation, but suggested that figures 3-6 ... "appear referable to Areosphaeridium multicornutum."
Allocations of the specimens illustrated by Cookson and Eisenack (1965, pl. 15, figs. 1-9) and initially identified as Cordosphaeridium capricornum are: figure I is interpreted as possibly a dorsal view of a specimen of Enneadocysta harrisii; figures 2-3, 5-8 are considered specimens of Cooksonidium capricornum; figure 4 is regarded as a representative of the undescribed species Enneadocysta sp. C, and figure 9 is believed to be an operculum of Enneadocysta harrisii.
Affinities: (p. 107-108):
Cooksonidium capricornum differs from Emmetrocysta urnaformis (Cookson 1953) Stover 1975 in possessing intratabular process complexes as well as single-stemmed processes (pl. 7, figs. 5a-b). Except for the antapical process complex on Cooksonidium capricornum, which is roundly heart-shaped (pl. 7, figs. 6, 7) and has a distal trabeculum, the other process complexes are arcuate with free distal ends. On Emmetrocysta urnaformis the complexes are more or less cylindrical and have distal ring trabeculae. Both species lack paracingular processes and have their hypocystal processes arranged in the standard sexiform pattern. Cooksonidium capricornum differs from Enneadocysta harrisii by having process complexes as well as single-stemmed intratabular processes and a standard sexiform rather than a partiform hypocystal configuration.
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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.
Cooksonidium capricornum (Cookson and Eisenack, 1965a) Stover and Williams, 1995. According to Stover and Williams (1994), this species has 16 to 18 processes or process complexes, 10 or 11 on the epicyst and 6 or 7 on the hypocyst. There are no paracingular processes. Single processes distally have licrate or flared tips. The process complexes usually have two to four stems, with up to eight on the antapical plate, which is usually cardioform. In the process complexes, the distal ends of the stems are connected by a finely denticulate trabecula that commonly extends beyond the limits of the proximal ridge. Process formula is 4', 6", 0c, 5"’, 0-1p, 1"”, as. Six precingular processes and sometimes an anterior sulcal. Commonly process complexes on 3", 4" and 5", 2" and 6" may have single processes or process complexes. 1" and the anterior sulcal have single processes. Usually seven hyocystal processes: five postcingulars, one posterior intercalary and one antapical . Process on paraplate 1p may be missing. Paraplates 2"’, 3"’ and 4"’ have process complexes, 5"’ may have a single process or a complex. 1"’ and 1p are single processes.
Size body diameter 50- 63 µm, overall 75-110 µm.
Holotype: Cookson and Eisenack, 1965, pl. 15, fig.7
Locus typicus: Browns Creek Clays (outwash section), Aire District, Victoria, Australia.
Stratum typicum: Upper Eocene (Priabonian) carbonaceous clay about 13.1 m above the Notostrea Greensand, Browns Creek Clays
Stratigraphic age and occurrence: Late Eocene; reported only from the type locality.
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Original description as Cordosphaeridium capricornum: [Cookson and Eisenack 1965, p. 128-129]:
Description:
Shell approximately spherical with numerous radially arranged appendages of characteristic form which vary in number in individual specimens and in size, form, and structure in one and the same specimen. All are solid; sorne are simple with unbranched or slightly branched apices or with terminal bifurcations which extend laterally and are upwardly or downwardly curved; others are broadly flattened and perforated to varying degrees with broad apices which narrow gradually as they curve backwards towards the shell. The upper surface of the apices and their extensions are consistently finely denticulate (Pl. 15, fig. 8, 9). The bases of the larger appendages are semicircular to, occasionally, almost circular, and similarly the tips of the apical prolongations sometimes appear to touch but, in reality, are never connected. The appendages are sometimes faintly and longitudinally striated; shorter and more pronounced striations may be evident at or near their points of origin. The surface of the shell is faintly granular.
The archeopyle is apical, the operculum bearing four appendages, two relatively large and two small (Pl. 15, fig. 9).
At the antapex an approximately circular area, outlined either completely (Pl. 15, fig. 6) or incompletely by a ridge to which a few small simple appendages may or may not be attached, has been seen. Such an area is suggestive of an antapical field.
Dimensions:
Holotype, overall width c. 78 µm, width of shell c. 52 µm.
Range, overall width c. 70-94 µm, width of shell c. 43-52 µm; appendages c. 18-30 µm long.
Affinities/Comment:
In the holotype the distribution of the appendages on the two surfaces differs. On the one shown in Pl. 15, fig. 7 there is a relatively large appendage-free area, whereas on the other surface the appendages are more evenly distributed. In the paratype (Pl. 15, fig. 2, 3) an almost circular antapical ridge supports a number of long thread-like appendages, the broadened apices of which unite to form an almost complete distal ring. At present the significance and constancy of such features cannot be estimated. C. capricornum is one of the most frequent forms in the greensand and higher deposits in the Browns Creek section.
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Emended description:
Stover and Williams, 1995, p. 107-108:
Description:
Shape: Cysts skolochorate with subspherical central body.
Wall relationships: Autophragm only.
Wall features: Autophragm finely granulate to pitted except on processes; central body with 16 to 18 intratabular single processes or process complexes, 10 or 11 on epicyst and six or seven on hypocyst, paracingular processes absent. On processes with single stems, the stems are solid, smooth or faintly fibroid, tapered distally and have slightly expanded bases. Distally they have licrate or flared tips and ends of the latter may be recurved. Process complexes composed of solid, faintly fibroid or smooth stems which extend from low, arcuate or heart-shaped proximal ridges. Usually two to four stems per arcuate process complex and up to eight stems on the antapical, generally cardioform, process complex. Stems in process complexes may be fenestrate and expanded proximally as well as distally. In each arcuate process complex the distal ends of stems are connected by a finely denticulate trabecula that commonly extends beyond the limits of the proximal ridge. In antapical complex a distal, usually complete denticulate trabeculum connects ends of stems. Trabeculae absent between process complexes or individual processes.
Excystment Type: Archeopyle apical; operculum tetratabular, simple, more or less equidimensional and free.
Paratabulation: Gonyaulacoid; expressed on epicyst by principal and accessory archeopyle sutures and by the locations of intratabular features, on hypocyst by positions of intratabular or penitabular structures only. Process formula 4', 6'', 0c, 5''', 0-1p, 1'''', 1as. Six precingular processes present subjacent to the archeopyle margin and an anterior parasulcal process may be present or absent. Structures on paraplates 3'' to 5'' frequently process complexes, less commonly individual processes; paraplates 2'' and 6'' may have single processes or process complexes; paraplates 1'' and the anterior sulcal have single processes. Paraplate 1'' is narrower than 6'' and the ends of arcuations of precingular processes with licrate tips are directed equatorially. Usually seven hypocystal processes: five postcingulars, one posterior intercalary and one antapical, arranged in the standard sexiform paratabulation pattern. Process on paraplate 1p may be missing. Paraplates 2''', 3''' and 4''' have process complexes, paraplate 5''' may have a single process or a process complex, paraplates 1''' and 1p have single processes and antapical paraplate has a roundly polygonal to heart-shaped process complex. Ends of the hypocystal dorsal process complexes generally point equatorially.
Paracingulum: Paracingular area devoid of processes.
Parasulcus: Usually a well-developed parasulcal notch with sometimes a single anterior sulcal process.
Dimensions:
Intermediate to large; measurements of 10 specimens: body diameter 50 µm (55 µm) 63 µm, overall diameter 75 µm (90 µm) 110 µm, process length 15 µm (23 µm) 32 µm, single process width 2.5 µm to 20 µm, most less than 8 µm wide at mid-length, process complex width 10 µm to 24 µm, most in the 16 µm to 20 µm range, width of single process tips 10 µm to 16 µm and width of process complex tips 30 µm to 40 µm. Mean values shown in parentheses.
Remarks:
Sarjeant (1981) regarded Cordosphaeridium capricornum as conspecific with and taxonomically junior to Areosphaeridium dictyostilum. His list of synonyms and other citations for Areosphaeridium dictyostilum includes the following entry: "1965a Cordosphaeridium capricornum Cookson and Eisenack, p. 128-129, pl. 15, figs. 1, ?2, 7-9." This citation excludes Cookson and Eisenack's figure 3, which is a different focus level of the specimen they showed as figure 2 but presented upside down, as well as figures 4-6. Sarjeant provided no definitive information about the dispositions of the figured specimens not included in the above quotation, but suggested that figures 3-6 ... "appear referable to Areosphaeridium multicornutum."
Allocations of the specimens illustrated by Cookson and Eisenack (1965, pl. 15, figs. 1-9) and initially identified as Cordosphaeridium capricornum are: figure I is interpreted as possibly a dorsal view of a specimen of Enneadocysta harrisii; figures 2-3, 5-8 are considered specimens of Cooksonidium capricornum; figure 4 is regarded as a representative of the undescribed species Enneadocysta sp. C, and figure 9 is believed to be an operculum of Enneadocysta harrisii.
Affinities: (p. 107-108):
Cooksonidium capricornum differs from Emmetrocysta urnaformis (Cookson 1953) Stover 1975 in possessing intratabular process complexes as well as single-stemmed processes (pl. 7, figs. 5a-b). Except for the antapical process complex on Cooksonidium capricornum, which is roundly heart-shaped (pl. 7, figs. 6, 7) and has a distal trabeculum, the other process complexes are arcuate with free distal ends. On Emmetrocysta urnaformis the complexes are more or less cylindrical and have distal ring trabeculae. Both species lack paracingular processes and have their hypocystal processes arranged in the standard sexiform pattern. Cooksonidium capricornum differs from Enneadocysta harrisii by having process complexes as well as single-stemmed intratabular processes and a standard sexiform rather than a partiform hypocystal configuration.
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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.
Cooksonidium capricornum (Cookson and Eisenack, 1965a) Stover and Williams, 1995. According to Stover and Williams (1994), this species has 16 to 18 processes or process complexes, 10 or 11 on the epicyst and 6 or 7 on the hypocyst. There are no paracingular processes. Single processes distally have licrate or flared tips. The process complexes usually have two to four stems, with up to eight on the antapical plate, which is usually cardioform. In the process complexes, the distal ends of the stems are connected by a finely denticulate trabecula that commonly extends beyond the limits of the proximal ridge. Process formula is 4', 6", 0c, 5"’, 0-1p, 1"”, as. Six precingular processes and sometimes an anterior sulcal. Commonly process complexes on 3", 4" and 5", 2" and 6" may have single processes or process complexes. 1" and the anterior sulcal have single processes. Usually seven hyocystal processes: five postcingulars, one posterior intercalary and one antapical . Process on paraplate 1p may be missing. Paraplates 2"’, 3"’ and 4"’ have process complexes, 5"’ may have a single process or a complex. 1"’ and 1p are single processes.
Size body diameter 50- 63 µm, overall 75-110 µm.