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Rotosphaeropsis thula
Rotosphaeropsis thula (Davey, 1982b, p.26–27, pl.8, figs.7–11) Riding and Davey, 1989, p.109. Emendation: Riding and Davey, 1989, p.109,112, as Rotosphaeropsis thule.
Originally Cannosphaeropsis, subsequently (and now) Rotosphaeropsis.
Holotype: Davey, 1982, pl.8, fig. 8-11; Riding and Davey, 1989, pl.1, fig.4
Locus typicus: West Abbey, Norfolk, England
Stratum typicum: Early Ryazanian
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP
Rotosphaeropsis thule (Davey, 1982b) Riding and Davey, 1989, emend. Riding and Davey, 1989. According to Riding and Davey (1989, p.109,112), Rotosphaeropsis thule is ovoidal in overall shape with little, if any, dorso-ventral flattening. Cyst apparently two-layered, the two layers being closely appressed except where the periphragm also forms the processes; cyst wall smooth to scabrate. Cyst body covered by numerous, slender, solid, parasutural processes at both gonal and intergonal positions. The processes are variable in length from 12% to 73% of the cyst body width; they are generally longest on the hypocyst and shorter on the epicyst. The majority of the processes flare distally where they are consistently interconnected by parasutural trabeculae. The elements of the trabeculae are normally similar in width to the processes, but may broaden markedly and bear distally low, irregularly-spaced spines or denticles. Paratabulation sexiform gonyaulacacean, indicated by trabeculae. Kofoidian formula 4', 6", ?6c, 6"', 1p, 1"", 5s. Paracingular and parasulcal trabeculae are rarely discernible and the former may be partially suppressed. Parasulcus longitudinal (L-type). Archeopyle precingular type P (3"), operculum free. Size; overall length 48-84 µm, overall width 38-72 µm, process length 9-28 µm. Note: Rotosphaeropsis differs from Cannosphaeropsis in sulcal organization, being L- rather than S-type. R.thule also has intraparasulcal trabeculae. R. thule differs from R. munu in having a less elongated body and fewer and shorter processes.
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Original diagnosis: Davey, 1982, p. 26-27: Cannosphaeropsis thula
Shape: The pericyst, excluding processes, is ovoidal to oviform with very little dorso-ventral flattening.
Wall: The cyst wall is apparently two-layered, the two layers being closely appressed except where the periphragm alone forms the processes. The wall is of moderate thickness and the surface is smooth to little pitted.
Paratabulation: Parasutures are occasionally visible along the paracingulum and, more rarely, surrounding the parasulcal area. Processes: These are parasutural in position. The gonal processes are trifurcate distally whereas the parasutural processes bifurcate distally. The furcaions join with neighbouring ones to form a trabeculum which reflects the paratabulation. Distally the trabeculum bears small spines. The processes are longest on the dorsal hypocyst and decrease in size away from this region, beiing lowest on the ventral epicyst.
Archaeopyle: Precingular, Type P(3'' only), with free operculum.
Original description: Davey, 1982, p. 27: Cannosphaeropsis thula
The number of parasutural processes tends to increase in the lower Portlandian to upper Kimmeridgian and are often free distally. In these forms the trabeculum tends to become more irregular.
Emended diagnosis: Riding and Davey, 1989, p. 109, 112
A species of Rotosphaeropsis, ovoidal in overall shape with little, if any, dorso-ventral flattening. Cyst apparently two-layered, the two layers being closely appressed except where the periphragm alone forms the processes; cyst wall smooth to scabrate. Cyst body covered by numerous, slender, solid, parasutural processes at both gonal and intergonal positions. The processes are variable in length, from 12% to 73% of the cyst body width; they are generally longest on the hypocyst and shorter on the epicyst. The majority of the processes flare distally where they are consistently interconnected by parasutural trabeculae.The elements of the trabeculae are normally similar in width to the processes, but may broaden markedly and bear distally low, irregularly-spaced spines or denticles. Paratabulation sexiform gonyaulacacean, indicated by trabeculae, Kofoidian formula: 4', 6", ?6c, 6''', 1p,1'''', 5s. Paracingular and parasulcal trabeculae are rarely discernible and the former may be partially suppressed. Parasulcus longitudinal (L-type of Evitt, 1985). Archaeopyle precingular, type P (3"), operculum free. Size, small to intermediate. Dimensions. Overall cyst length: 48-84 µm. Overall cyst width: 38-72 µm. Process length: 9-28 µm.
Affinities:
Riding and Davey, 1989, p. 112: This species has been transferred to Rotosphaeropsis Davey 1987 as it exhibits distal trabeculae surmounting irregularly-spaced parasutural processes, a precingular archaeopyle and lacks Spiniferites-type processes. The basionym genus, Cannosphaeropsis, although superficially similar in terms of basic cyst organisation, shape and archaeopyle type, is inappropriate as it differs markedly in crucial details of paratabulation and morphology. R. thula comb. nov., emend. nov. has a longitudinal parasulcus; Cannosphaeropsis, by virtue of its position within the Spiniferites complex, has a sigmoidal ventral area. Certain topological paratabulation differences associated with L-type and S-type parasulci therefore exist between R. thula and Cannosphaeropsis, for example the former has a subparallel sided 6" paraplate whereas the equivalent in the latter is pseudotriangular (see Evitt, 1985 fig. 5.8B). In addition, R. thula exhibits intraparasulcal trabeculae (Pl. 1, fig. 1), features not associated with Spiniferites and its allies. Rotosphaeropsis thula lacks the characteristic (of Cannosphaeropsis) triradiate branches at gonal points and the paired branches located intergonally on the trabeculae (see Plate 1, fig. 10). Cannosphaeropsis exhibits a much reduced number of gonal processes and entirely lacks intergonal shafts, a situation differing markedly with the full complement of gonal processes together with the numerous intergonals of R. thula. The distally flared processes and thickened trabeculae of R. thula are unknown in Cannosphaeropsis. The processes of R. thula are very variable in length. The paratabulation is readily discernible in forms with low parasutural processes although morphotypes with longer shafts tend to be distorted making the paratabulation difficult to interpret. Davey (1982) commented that the number of processes is greater in specimens from the Upper Kimmeridgian to lowermost Portlandian. Rotosphaeropsis thula differs from R. munu, the type species, in that the cyst body of the former is less elongate; R. munu has considerably more numerous processes, which are consistently longer than those of R. thula. Medial/distal cross linkage of processes, in addition to the trabeculae, are characteristic of R. munu but are not exhibited by R. thula. Because of the relatively long and complex processes of R. munu, the trabeculae are invariably distorted and the detailed paratabulation cannot be established.
Originally Cannosphaeropsis, subsequently (and now) Rotosphaeropsis.
Holotype: Davey, 1982, pl.8, fig. 8-11; Riding and Davey, 1989, pl.1, fig.4
Locus typicus: West Abbey, Norfolk, England
Stratum typicum: Early Ryazanian
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP
Rotosphaeropsis thule (Davey, 1982b) Riding and Davey, 1989, emend. Riding and Davey, 1989. According to Riding and Davey (1989, p.109,112), Rotosphaeropsis thule is ovoidal in overall shape with little, if any, dorso-ventral flattening. Cyst apparently two-layered, the two layers being closely appressed except where the periphragm also forms the processes; cyst wall smooth to scabrate. Cyst body covered by numerous, slender, solid, parasutural processes at both gonal and intergonal positions. The processes are variable in length from 12% to 73% of the cyst body width; they are generally longest on the hypocyst and shorter on the epicyst. The majority of the processes flare distally where they are consistently interconnected by parasutural trabeculae. The elements of the trabeculae are normally similar in width to the processes, but may broaden markedly and bear distally low, irregularly-spaced spines or denticles. Paratabulation sexiform gonyaulacacean, indicated by trabeculae. Kofoidian formula 4', 6", ?6c, 6"', 1p, 1"", 5s. Paracingular and parasulcal trabeculae are rarely discernible and the former may be partially suppressed. Parasulcus longitudinal (L-type). Archeopyle precingular type P (3"), operculum free. Size; overall length 48-84 µm, overall width 38-72 µm, process length 9-28 µm. Note: Rotosphaeropsis differs from Cannosphaeropsis in sulcal organization, being L- rather than S-type. R.thule also has intraparasulcal trabeculae. R. thule differs from R. munu in having a less elongated body and fewer and shorter processes.
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Original diagnosis: Davey, 1982, p. 26-27: Cannosphaeropsis thula
Shape: The pericyst, excluding processes, is ovoidal to oviform with very little dorso-ventral flattening.
Wall: The cyst wall is apparently two-layered, the two layers being closely appressed except where the periphragm alone forms the processes. The wall is of moderate thickness and the surface is smooth to little pitted.
Paratabulation: Parasutures are occasionally visible along the paracingulum and, more rarely, surrounding the parasulcal area. Processes: These are parasutural in position. The gonal processes are trifurcate distally whereas the parasutural processes bifurcate distally. The furcaions join with neighbouring ones to form a trabeculum which reflects the paratabulation. Distally the trabeculum bears small spines. The processes are longest on the dorsal hypocyst and decrease in size away from this region, beiing lowest on the ventral epicyst.
Archaeopyle: Precingular, Type P(3'' only), with free operculum.
Original description: Davey, 1982, p. 27: Cannosphaeropsis thula
The number of parasutural processes tends to increase in the lower Portlandian to upper Kimmeridgian and are often free distally. In these forms the trabeculum tends to become more irregular.
Emended diagnosis: Riding and Davey, 1989, p. 109, 112
A species of Rotosphaeropsis, ovoidal in overall shape with little, if any, dorso-ventral flattening. Cyst apparently two-layered, the two layers being closely appressed except where the periphragm alone forms the processes; cyst wall smooth to scabrate. Cyst body covered by numerous, slender, solid, parasutural processes at both gonal and intergonal positions. The processes are variable in length, from 12% to 73% of the cyst body width; they are generally longest on the hypocyst and shorter on the epicyst. The majority of the processes flare distally where they are consistently interconnected by parasutural trabeculae.The elements of the trabeculae are normally similar in width to the processes, but may broaden markedly and bear distally low, irregularly-spaced spines or denticles. Paratabulation sexiform gonyaulacacean, indicated by trabeculae, Kofoidian formula: 4', 6", ?6c, 6''', 1p,1'''', 5s. Paracingular and parasulcal trabeculae are rarely discernible and the former may be partially suppressed. Parasulcus longitudinal (L-type of Evitt, 1985). Archaeopyle precingular, type P (3"), operculum free. Size, small to intermediate. Dimensions. Overall cyst length: 48-84 µm. Overall cyst width: 38-72 µm. Process length: 9-28 µm.
Affinities:
Riding and Davey, 1989, p. 112: This species has been transferred to Rotosphaeropsis Davey 1987 as it exhibits distal trabeculae surmounting irregularly-spaced parasutural processes, a precingular archaeopyle and lacks Spiniferites-type processes. The basionym genus, Cannosphaeropsis, although superficially similar in terms of basic cyst organisation, shape and archaeopyle type, is inappropriate as it differs markedly in crucial details of paratabulation and morphology. R. thula comb. nov., emend. nov. has a longitudinal parasulcus; Cannosphaeropsis, by virtue of its position within the Spiniferites complex, has a sigmoidal ventral area. Certain topological paratabulation differences associated with L-type and S-type parasulci therefore exist between R. thula and Cannosphaeropsis, for example the former has a subparallel sided 6" paraplate whereas the equivalent in the latter is pseudotriangular (see Evitt, 1985 fig. 5.8B). In addition, R. thula exhibits intraparasulcal trabeculae (Pl. 1, fig. 1), features not associated with Spiniferites and its allies. Rotosphaeropsis thula lacks the characteristic (of Cannosphaeropsis) triradiate branches at gonal points and the paired branches located intergonally on the trabeculae (see Plate 1, fig. 10). Cannosphaeropsis exhibits a much reduced number of gonal processes and entirely lacks intergonal shafts, a situation differing markedly with the full complement of gonal processes together with the numerous intergonals of R. thula. The distally flared processes and thickened trabeculae of R. thula are unknown in Cannosphaeropsis. The processes of R. thula are very variable in length. The paratabulation is readily discernible in forms with low parasutural processes although morphotypes with longer shafts tend to be distorted making the paratabulation difficult to interpret. Davey (1982) commented that the number of processes is greater in specimens from the Upper Kimmeridgian to lowermost Portlandian. Rotosphaeropsis thula differs from R. munu, the type species, in that the cyst body of the former is less elongate; R. munu has considerably more numerous processes, which are consistently longer than those of R. thula. Medial/distal cross linkage of processes, in addition to the trabeculae, are characteristic of R. munu but are not exhibited by R. thula. Because of the relatively long and complex processes of R. munu, the trabeculae are invariably distorted and the detailed paratabulation cannot be established.