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Circulodinium
From Fensome et al., 2019:
Circulodinium, Alberti, 1961, p.28.
Emendations: McLachlan et al., 2018, p.681–682; Fensome et al., 2019a, p.36.
Taxonomic senior synonyms: Canningia, according to Eisenack (1964, p.322) (not Millioud 1969, p.425 as indicated in Fensome and Williams 2004 -- see Fensome et al., 2019a, p.3 for discussion) -- however, Jansonius (1986, p.204) retained Circulodinium; Cyclonephelium, according to Davey (1978, p.894) and Fensome et al. (2009, p.24) -- however, Jansonius (1986, p.204) and McLachlan et al. (2018, p.681–682) retained Circulodinium. Duxbury (2002, p.78) considered that Circulodinium may be a taxonomic junior synonym of Tenua Eisenack.
Type: Alberti, 1961, pl.4, fig.20, as Circulodinium hirtellum.
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Original description: [Alberti, 1961]: (Translation: LPP):
Diagnosis:
Shell flattened to flat, in outline more or less circular to irregularly rounded. With a small, distally slightly blunted apical projection. Hypotheca indented antapically, producing two antapical bulges, one of which may be more or less reduced. Shell without transverse furrow, untabulated. Its surface, except for the dorsal and ventral centre and the antapical indentation, set with short, solid, partially distally widened in a paddle-shaped fashion, rarely furcate thorns.
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Emended description:
Jansonius, 1986
Diagnosis:
Proximate cysts, more or less dorso-ventrally flattened (lenticular or concavo-convex); outline subcircular to polygonal, commonly with a small apical prominence and one, or two unequal, antapical prominence(s), although the antapex may be rounded. Wall apparently single-layered, ornamented with free elements of varying length and shape, usually spines with capitate or bifurcate tips, in part distally broadened to a paddle shape, generally more strongly developed in peripheral regions, more or less strongly reduced in size and density in central ventral and dorsal regions.
Archeopyle apical, principal suture angled, accessory sutures lacking or short, operculum free or attached.
Paratabulation or cingulum generally not indicated; sulcal notch off-set to left.
Remarks:
When Cyclonephelium was proposed, Deflandre and Cookson (1955) assigned four species; of these, two were later transferred to Glaphyrocysta. C. compactum remains the nomenclatural type of the genus in a strict sense; C. distinctum is here transferred to Circulodinium. Since Sarjeant (1985) concluded that Tenua is a senior synonym of Cerbia, the genus Circulodinium now is the preferred receptacle for cysts of the general type of C. hirtellum, its nomenclatural type. In Sentusidinium there is no dorso-ventral flattening, no reduction of sculpture in the central regions, and the sulcal notch is not displaced toward the left. It is not clear why Sarjeant and Stover (1978) ignored the genus Circulodinium and its type species.
Circulodinium, Alberti, 1961, p.28.
Emendations: McLachlan et al., 2018, p.681–682; Fensome et al., 2019a, p.36.
Taxonomic senior synonyms: Canningia, according to Eisenack (1964, p.322) (not Millioud 1969, p.425 as indicated in Fensome and Williams 2004 -- see Fensome et al., 2019a, p.3 for discussion) -- however, Jansonius (1986, p.204) retained Circulodinium; Cyclonephelium, according to Davey (1978, p.894) and Fensome et al. (2009, p.24) -- however, Jansonius (1986, p.204) and McLachlan et al. (2018, p.681–682) retained Circulodinium. Duxbury (2002, p.78) considered that Circulodinium may be a taxonomic junior synonym of Tenua Eisenack.
Type: Alberti, 1961, pl.4, fig.20, as Circulodinium hirtellum.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Alberti, 1961]: (Translation: LPP):
Diagnosis:
Shell flattened to flat, in outline more or less circular to irregularly rounded. With a small, distally slightly blunted apical projection. Hypotheca indented antapically, producing two antapical bulges, one of which may be more or less reduced. Shell without transverse furrow, untabulated. Its surface, except for the dorsal and ventral centre and the antapical indentation, set with short, solid, partially distally widened in a paddle-shaped fashion, rarely furcate thorns.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Jansonius, 1986
Diagnosis:
Proximate cysts, more or less dorso-ventrally flattened (lenticular or concavo-convex); outline subcircular to polygonal, commonly with a small apical prominence and one, or two unequal, antapical prominence(s), although the antapex may be rounded. Wall apparently single-layered, ornamented with free elements of varying length and shape, usually spines with capitate or bifurcate tips, in part distally broadened to a paddle shape, generally more strongly developed in peripheral regions, more or less strongly reduced in size and density in central ventral and dorsal regions.
Archeopyle apical, principal suture angled, accessory sutures lacking or short, operculum free or attached.
Paratabulation or cingulum generally not indicated; sulcal notch off-set to left.
Remarks:
When Cyclonephelium was proposed, Deflandre and Cookson (1955) assigned four species; of these, two were later transferred to Glaphyrocysta. C. compactum remains the nomenclatural type of the genus in a strict sense; C. distinctum is here transferred to Circulodinium. Since Sarjeant (1985) concluded that Tenua is a senior synonym of Cerbia, the genus Circulodinium now is the preferred receptacle for cysts of the general type of C. hirtellum, its nomenclatural type. In Sentusidinium there is no dorso-ventral flattening, no reduction of sculpture in the central regions, and the sulcal notch is not displaced toward the left. It is not clear why Sarjeant and Stover (1978) ignored the genus Circulodinium and its type species.