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Cassiculosphaeridia solida
Cassiculsphaeridia solida, Riding and Helby, 2001g, p.199-200, figs.10A-P.
Holotype: Riding and Helby, 2001g, figs.10E-G.
Stratigraphical distribution: ranges from the Oxfordian Waneae spectabilis Zone (6c) to the Tithonian upper Dingodinium jurassicum Zone 5a. It forms a marker acme in the upper part of the lower D. jurassicum Zone (5bi)
Age: Oxfordian-Tithonian.
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Original description: [Riding & Helby, 2001g]:
Description:
A species of Cassiculosphaeridia, intermediate in size and with an ellipsoidal to subcircular outline. The autophragm is extremely thick (1.5-4µm) and covered with strong, corrugate ornamentation. The ornamentation comprises an irregular network of discontinuous, arcuate, anastomosing ridges 1-4 µm in height and 2-6µm wide. These ridges frequently form an irregular reticulate pattern, the muri enclosing subcircular to subpolygonal lacunae 1-6µm in diameter. The ridges may be short and occasionally form isolated irregular verrucae.
Indications of paratabulation are lacking except for the principal archaeopyle suture, which is angular and indicative of four apical and six precingular paraplates. Accessory archaeopyle sutures may be present. Rarely, a small (2-4µm high) apical protuberance may be developed.
Dimensions (µm, n=27): Min. (Mean) Max.:
Length of entire cyst: 72 (79) 89
Length of loisthocyst: 53 (67) 80
Length of operculum: 15 (20) 27
Equatorial width: 58 (74) 91
Width of archaeopyle: 37 (53) 72
The measured specimens are from a sidewall core sample from Yering-1 well at 2563.50m and ditch cuttings samples from Crux-1 well between 3045.00-3050.00m and 2945.00m-2950.00m.
Remarks:
This species of Cassiculosphaeridia is characterized by the extremely thick autophragm, covered by prominent ridges, which form a corrugate-rugulate ornamentational pattern. The ridges are highly variable and form a discontinuous and anastomosing configuration. This variability ranges from short, irregular ridges giving a pseudo-verrucate pattern to longer elements which form a course reticulum. The angular nature of the principal archaeopyle suture is indicative of a gonyaulacacean paratabulation pattern. The lack of indications of paratabulation means that the orientation is difficult in specimens where the archaeopyle has not opened. The species is frequently flattened during preservation and this tends to artificially expand the diameter of the archaeopyle. Due to the characteristic ornamentation, isolated opercula are commonly identified. The lack of both paratabulation and ectophragm precludes the assignment of this species to Ellipsodictyum Klement 1960 or Valensiella Eisenack 1963 respectively (see Stover & Evitt, 1978). Courtinat (1989, p. 182) considered Cassiculosphaeridia to be a junior synonym of Valensiella and transferred all species of Cassiculosphaerida to Valensiella. Lentin & Williams (1993, p. 82, 83) accepted these transfers. Subsequently, Slimani (1994) retained Cassiculosphaeridia. Williams et al. (1998) followed the Slimani interpretation.
Affinities:
Cassiculosphaeridia solida differs from the other species of the genus in its distinctive, extremely thick autophragm and robust, highly irregular arcuate/reticulate ridges. The majority of the other species of Cassiculosphaeridia have a regular reticulum and are smaller than C. solida. Cassiculosphaeridia magna Davey 1974 and C? tocheri Schioler 1993 are similar in size to C. solida. Furthermore the ridges/crests in C. magna are also anastomosing (Davey, 1974). However, C. magna has smaller ridges that form a denser reticulate pattern than those in C. solida; and C? tocheri has a regular reticulum. Both c. magna and C? tocheri have a significantly thinner autophragm than C. solida. In terms of ornamentation, the most similar species to C. solida is C. tunicate Harding ( in Williams et al., 1998). This species has relatively few prominent, arcuate/anastomosing ridges (Harding, 1990, pl. 27, figs 9-14). However, C. tunicate is considerably smaller than C. solida and the former species is holocavate, has a relatively thin autophragm and the lumina formed by the ridges have a wide range of diameters. A similar, but less robust, unnamed form is recorded in the Tithonian lower Pseudoceratium iehiense Zone (4ciii) on the North-West Shelf. Cassiculosphaeridia pygmaeus Stevens 1987 is much smaller, more delicate and regular fenestration and is commonly more ellipsoidal than C. solida.
Holotype: Riding and Helby, 2001g, figs.10E-G.
Stratigraphical distribution: ranges from the Oxfordian Waneae spectabilis Zone (6c) to the Tithonian upper Dingodinium jurassicum Zone 5a. It forms a marker acme in the upper part of the lower D. jurassicum Zone (5bi)
Age: Oxfordian-Tithonian.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Riding & Helby, 2001g]:
Description:
A species of Cassiculosphaeridia, intermediate in size and with an ellipsoidal to subcircular outline. The autophragm is extremely thick (1.5-4µm) and covered with strong, corrugate ornamentation. The ornamentation comprises an irregular network of discontinuous, arcuate, anastomosing ridges 1-4 µm in height and 2-6µm wide. These ridges frequently form an irregular reticulate pattern, the muri enclosing subcircular to subpolygonal lacunae 1-6µm in diameter. The ridges may be short and occasionally form isolated irregular verrucae.
Indications of paratabulation are lacking except for the principal archaeopyle suture, which is angular and indicative of four apical and six precingular paraplates. Accessory archaeopyle sutures may be present. Rarely, a small (2-4µm high) apical protuberance may be developed.
Dimensions (µm, n=27): Min. (Mean) Max.:
Length of entire cyst: 72 (79) 89
Length of loisthocyst: 53 (67) 80
Length of operculum: 15 (20) 27
Equatorial width: 58 (74) 91
Width of archaeopyle: 37 (53) 72
The measured specimens are from a sidewall core sample from Yering-1 well at 2563.50m and ditch cuttings samples from Crux-1 well between 3045.00-3050.00m and 2945.00m-2950.00m.
Remarks:
This species of Cassiculosphaeridia is characterized by the extremely thick autophragm, covered by prominent ridges, which form a corrugate-rugulate ornamentational pattern. The ridges are highly variable and form a discontinuous and anastomosing configuration. This variability ranges from short, irregular ridges giving a pseudo-verrucate pattern to longer elements which form a course reticulum. The angular nature of the principal archaeopyle suture is indicative of a gonyaulacacean paratabulation pattern. The lack of indications of paratabulation means that the orientation is difficult in specimens where the archaeopyle has not opened. The species is frequently flattened during preservation and this tends to artificially expand the diameter of the archaeopyle. Due to the characteristic ornamentation, isolated opercula are commonly identified. The lack of both paratabulation and ectophragm precludes the assignment of this species to Ellipsodictyum Klement 1960 or Valensiella Eisenack 1963 respectively (see Stover & Evitt, 1978). Courtinat (1989, p. 182) considered Cassiculosphaeridia to be a junior synonym of Valensiella and transferred all species of Cassiculosphaerida to Valensiella. Lentin & Williams (1993, p. 82, 83) accepted these transfers. Subsequently, Slimani (1994) retained Cassiculosphaeridia. Williams et al. (1998) followed the Slimani interpretation.
Affinities:
Cassiculosphaeridia solida differs from the other species of the genus in its distinctive, extremely thick autophragm and robust, highly irregular arcuate/reticulate ridges. The majority of the other species of Cassiculosphaeridia have a regular reticulum and are smaller than C. solida. Cassiculosphaeridia magna Davey 1974 and C? tocheri Schioler 1993 are similar in size to C. solida. Furthermore the ridges/crests in C. magna are also anastomosing (Davey, 1974). However, C. magna has smaller ridges that form a denser reticulate pattern than those in C. solida; and C? tocheri has a regular reticulum. Both c. magna and C? tocheri have a significantly thinner autophragm than C. solida. In terms of ornamentation, the most similar species to C. solida is C. tunicate Harding ( in Williams et al., 1998). This species has relatively few prominent, arcuate/anastomosing ridges (Harding, 1990, pl. 27, figs 9-14). However, C. tunicate is considerably smaller than C. solida and the former species is holocavate, has a relatively thin autophragm and the lumina formed by the ridges have a wide range of diameters. A similar, but less robust, unnamed form is recorded in the Tithonian lower Pseudoceratium iehiense Zone (4ciii) on the North-West Shelf. Cassiculosphaeridia pygmaeus Stevens 1987 is much smaller, more delicate and regular fenestration and is commonly more ellipsoidal than C. solida.