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Cleistosphaeridium diversispinosum
From Fensome et al., 2019:
Cleistosphaeridium diversispinosum Davey et al., 1966, p.167, pl.10, fig.7. Emendation: Eaton et al., 2001, p.177. Holotype: Davey et al., 1966, pl.10, fig.7; Bujak et al., 1980, pl.7, figs.7–8; Islam, 1993, pl.1, figs.1–10; text-figs.1A–B; Eaton et al., 2001, figs.1A–B,2A–B; Fauconnier and Masure, 2004, pl.77, fig.9. Originally (and now) Cleistosphaeridium, subsequently Systematophora. Eaton et al. (2001, p.177) retained this species in Cleistosphaeridium. Taxonomic junior synonyms: Areosphaeridium polypetellum, according to Islam (1993, p.88) — however, Eaton et al. (2001, p.194) retained Cleistosphaeridium polypetellum; Circulodinium indicum Mehrotra and Sarjeant ex Lentin and Williams, according to Fensome et al. (2019a, p.54). Age: Early Eocene.
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Original description: [Davey et al., 1966, p.167]:
Diagnosis:
A Cleistosphaeridium with granular wall and polygonal archaeopyle. Processes solid, taeniate or tubular, usually slender and proximally expanded. Distal end forked or expanded.
Description:
This species is distinguished by the variable nature of the process ends. The expanded termination may be bifurcate, orthogonal and patulate, one branch may be larger than the other. The edges are usually denticulate and the processes may be up to 5 µm wide; but are usually about 2 µm. There is more than one process to a plate.
Dimensions:
Holotype: diameter of the body 38 µm, length of processes 9-16 µm.
Observed range: diameter of body 38 µm, length of processes 7-23 µm.
Affinities:
Only Cleistosphaeridium pectiniforme (Gerlach, 1961) resembles C. diversispinosum to any degree. It has widely forked processes with spinose margins; it does not, however, have a variability of process ending shown by our species.
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Comments Fensome et al., 2019a:
Circulodinium? indicum has slender processes, some of which appear to have dolabrate endings. As such, it is indistinguishable from Cleistosphaeridium diversispinosum, and hence we consider it a taxonomic junior synonym of that species. The name Cyclonephelium indicum was illegitimate in Mehrotra & Sarjeant (1987) because it was a junior homonym of Cyclonephelium indicum Khanna & Singh 1981. By “transferring” the species to Circulodinium, Lentin & Williams (1989, p. 63) effectively created a new name. According to Mehrotra & Sarjeant (1987, p. 163), the autophragm is “covered with numerous (usually exceeding 100) …” spines 6–10 μm long, which cover the cyst uniformly.
Stratigraphical occurrence. Davey et al. (1966) described Cleistosphaeridium diversispinosum from the Lower Eocene of southern England. Fensome et al. (2008) gave the LAD of this species as early Messinian (latest Miocene). Mehrotra & Sarjeant (1987) recovered Cyclonephelium indicum from the Paleocene of southern India.
Cleistosphaeridium diversispinosum Davey et al., 1966, p.167, pl.10, fig.7. Emendation: Eaton et al., 2001, p.177. Holotype: Davey et al., 1966, pl.10, fig.7; Bujak et al., 1980, pl.7, figs.7–8; Islam, 1993, pl.1, figs.1–10; text-figs.1A–B; Eaton et al., 2001, figs.1A–B,2A–B; Fauconnier and Masure, 2004, pl.77, fig.9. Originally (and now) Cleistosphaeridium, subsequently Systematophora. Eaton et al. (2001, p.177) retained this species in Cleistosphaeridium. Taxonomic junior synonyms: Areosphaeridium polypetellum, according to Islam (1993, p.88) — however, Eaton et al. (2001, p.194) retained Cleistosphaeridium polypetellum; Circulodinium indicum Mehrotra and Sarjeant ex Lentin and Williams, according to Fensome et al. (2019a, p.54). Age: Early Eocene.
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Original description: [Davey et al., 1966, p.167]:
Diagnosis:
A Cleistosphaeridium with granular wall and polygonal archaeopyle. Processes solid, taeniate or tubular, usually slender and proximally expanded. Distal end forked or expanded.
Description:
This species is distinguished by the variable nature of the process ends. The expanded termination may be bifurcate, orthogonal and patulate, one branch may be larger than the other. The edges are usually denticulate and the processes may be up to 5 µm wide; but are usually about 2 µm. There is more than one process to a plate.
Dimensions:
Holotype: diameter of the body 38 µm, length of processes 9-16 µm.
Observed range: diameter of body 38 µm, length of processes 7-23 µm.
Affinities:
Only Cleistosphaeridium pectiniforme (Gerlach, 1961) resembles C. diversispinosum to any degree. It has widely forked processes with spinose margins; it does not, however, have a variability of process ending shown by our species.
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Comments Fensome et al., 2019a:
Circulodinium? indicum has slender processes, some of which appear to have dolabrate endings. As such, it is indistinguishable from Cleistosphaeridium diversispinosum, and hence we consider it a taxonomic junior synonym of that species. The name Cyclonephelium indicum was illegitimate in Mehrotra & Sarjeant (1987) because it was a junior homonym of Cyclonephelium indicum Khanna & Singh 1981. By “transferring” the species to Circulodinium, Lentin & Williams (1989, p. 63) effectively created a new name. According to Mehrotra & Sarjeant (1987, p. 163), the autophragm is “covered with numerous (usually exceeding 100) …” spines 6–10 μm long, which cover the cyst uniformly.
Stratigraphical occurrence. Davey et al. (1966) described Cleistosphaeridium diversispinosum from the Lower Eocene of southern England. Fensome et al. (2008) gave the LAD of this species as early Messinian (latest Miocene). Mehrotra & Sarjeant (1987) recovered Cyclonephelium indicum from the Paleocene of southern India.