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Canningia
From Fensome et al., 2019:
Canningia, Cookson and Eisenack, 1960b, p.251.
Emendations: Dörhöfer and Davies, 1980, p.36; Below, 1981a, p.30 -- however, see Hedlund and Norris (1986, p.295); Helby, 1987, p.321–322; McLachlan et al. 2018, p.674–675.
Taxonomic junior synonym: Hashenia, according to Chen et al. (1988, p.16); Circulodinium, 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) and Helby (1987, p.321–322) retained Circulodinium. Dörhöfer and Davies (1980, p.36) indicated that Cookson and Eisenack (1961a, p.72) provided an emendation for Canningia; however the latter authors did not formally emend the genus.
Type: Cookson and Eisenack, 1960b, pl.38, fig.1, as Canningia reticulata.
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Original description: [Cookson and Eisenack, 1960]:
Description:
Shell flattened, roughly four-sided to almost circular with a slight apical prominence and a broadly indented base. The basal projections (corresponding to antapical horns) are either equal or unequal and frequently differ slightly in shape. An equatorial girdle is either absent or faintly indicated both on the surface or by reentrant angles at the sides. The shell opens by a proximal break which results in the complete detachment of the apical region.
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Modified description:
Stover and Evitt, 1978, p. 24
Synopsis: Cysts proximate, lenticular, with slight apical prominence and two antapical lobations; autophragm variously ornamented; ornamentation uniformly distributed, consisting of spines or processes of low to moderate relief; archeopyle apical, Type tA; parasulcal notch offset.
Description:
Shape: Lenticular; apical margin may be obtusely angular and antapical margin may have two subangular lobations.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Autophragm variously ornamented (scabrate to retirugulate), ornamentation uniformly distributed and of low to moderate relief; surface without spines or processes.
Paratabulation: Indicated by archeopyle only, or by archeopyle and paracingulum.
Archeopyle: Apical, Type tA; principal archeopyle suture zigzag with offset parasulcal notch; operculum free.
Paracingulum: Not indicated, or expressed faintly by small protrusions along the lateral margins at about midlength.
Parasulcus: Not indicated.
Size: Small to large.
Affinities:
Canningia differs from Cyclonephelium in being uniformly ornamented, whereas on Cyclonephelium the ornamentation is generally lacking or reduced in the midventral and middorsal areas. In addition, the ornamentation on Canningia tends to be less discrete and lower than on typical forms of Cyclonephelium. Canningia differs from Canninginopsis in lacking parasutural features.
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Emended descriptions:
Dörhöfer and Davies, 1980
Description:
Proximate dinoflagellate cyst with roughly five-sided to circular outline. Apex prominent, antapex broadly indented between two rounded antapical horns. Cingulum occasionally indicated by faint surface ornamentation and/or slight bulges representing postcingular horns. Surface smooth or with low but variable ornament. Archaeopyle (AI), formed along an asymmetrical zigzag suture line. Tabulation was not determined. Some species presently in Canningia do not exhibit the (AI) archaeopyle and are omitted from the genus. Their archaeopyle suture is symmetrical and the antapex founded.
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Below, 1981: (Translation: LPP)
Diagnosis:
Spheroidal to lenticular cyst of round to pentagonal shape. Apex rounded or with low apical bulge. Antapex rounded, flattened or with lobus. Cyst wall two layered. Periphragm smooth or ornamented. Endocyst towards inner cyst smooth. Between both membranes variously structured ?endopragmal filling. Surface rarely divided in paraplates of gonyaulacoid scheme, usually undivided. Paracingulum and parasulcus into cyst indented or missing. Archeopyle apical, Type "Aa". Operculum simple, attached or enlarged.
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Remark: Hedlund and Norris, 1986, did not accept the emendation by Below, 1981.
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Helby, 1987
Description:
Shape: Lenticular cyst, apicalmargin obtusely angular, antapical margin modified by two subangular, unequal lobes. Small lateral protrusions may mark paracingulum.
Wall features: Two layered, holocavate autophragm bearing processes varying in size, density and distribution, generally nontabular, less frequently penitabular or parasutural. Ectophragm usually reticulate, varying to rugoreticulate; occasionally, finely granulate or smooth.
Paratabulation: Indicated by archaeopyle and variably expressed parasutural features.
Archaeopyle: Apical, type (tA); principal archaeopyle suture zigzag with offset parasutural notch. Operculum usually free.
Paracingulum: Usually indicated by protrusion of parasutural ridges across dorsal surface, most evident at equator.
Parasulcus: Usually marked by absence or reduction in length of processes between wall layers. Where observed, parasulcus usually slightly sinuous moving from left ventral position on the epicyst to midventral position on the hypocyst.
Size: Small to large.
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Notes from Fensome et al., 2019a:
Synopsis. Areoligeracean cysts that are proximate, dorsoventrally compressed, lenticular, with asymmetrical to rounded antapex and a generally short apical prominence. Holocavate with generally narrow pericoel; the connections between endophragm and periphragm generally densely distributed and may be in linear (muri) or isolated elements (pillars). Periphragm continuous or discontinuous, generally smooth or with ornamentation of low relief. Archaeopyle apical, with formula A(1–4′); operculum free or attached; parasulcal notch offset to the left.
Remarks. Cookson and Eisenack (Citation1960, p. 251) provided the following description for Canningia:
Shell flattened, roughly five-sided to almost circular with a slight apical prominence and a broadly indented base. The basal projections (corresponding to antapical horns) are either equal or unequal and frequently differ slightly in shape. An equatorial girdle is either absent or faintly indicated both on the surface or by re-entrant angles at the sides. The shell opens by a proximal break which results in the complete detachment of the apical region.
Wall structure was clearly not considered an important feature of this genus at the outset. In contrast, as discussed above, we regard the wall structure to be a critical feature in distinguishing genera within the Cyclonephelium group, and define Canningia primarily on its holocavate wall structure.
Senoniasphaera is similar to Canningia in being cavate, but connecting structures are absent, sparse, or barely visible under the light microscope (see also discussion under Senoniasphaera). The pericoels are also generally broader in dorsoventral view in Senoniasphaera. In Renidinium, the walls are separated in mainly ventral marginal areas so that in apical view they project ventrally.
We consider the emendations of Canningia by Below (Citation1981) and Helby (1987) useful in developing our current concept of Canningia, but not that by Dörhöfer and Davies (Citation1980); see the introductory sections for a full discussion of the contributions of these authors. At present, the genus contains species with an overall holocavate structure (as in the type) and species in which the holocavation is restricted to the ambital periphery of the cyst. Separation of the latter group of species into their own genus might merit future consideration.
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McLachlan et al., 2018:
Emended diagnosis. Areoligeracean cysts that are proximate to proximochorate, with subpentagonal to pentagonal ambitus. Typically, one apical, two lateral, and two antapical horns of varying development. Holocavate, usually with numerous nontabular to contabular processes connecting autophragm and ectophragm. Less frequently, processes penitabular or sutural. Processes varying in size, density, and distribution; disjunct, encircling, or predominantly marginate. Autophragm protrudes into horns formed by ectophragm. Ectophragm ornamentation of low relief; reticulate, rugoreticulate, finely granulate, or smooth. Cingulum indicated by sutural ridges across dorsal surface. Sulcus demarcated by absence or reduction in length of ectophragm support structures; slightly sinuous, tracing from left ventral position on the epicyst to midventral position of the hypocyst. Tabulation indicated by archaeopyle and sutural features. Archaeopyle apical, with formula A(1–4'), operculum free; sulcal notch offset to the left.
Comparison. Canningia differs from Senoniasphaera in being subpentagonal to pentagonal, bearing lateral horn autophragm protrusion, and in possessing a more extensive network of ectophragm support structures.
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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.
Canningia Cookson and Eisenack, 1960b, emend. Helby, 1987. According to Helby (1987, p.322), this species has a lenticular body, subpentagonal in outline, two-layered and with or without indications of paratabulation. The autophragm bears processes of variable size, which may be nontabular, less frequently penitabular or parasutural. The ectophragm is usually reticulate, varying to rugo-reticulate, occasionally finely granular or smooth.
Canningia, Cookson and Eisenack, 1960b, p.251.
Emendations: Dörhöfer and Davies, 1980, p.36; Below, 1981a, p.30 -- however, see Hedlund and Norris (1986, p.295); Helby, 1987, p.321–322; McLachlan et al. 2018, p.674–675.
Taxonomic junior synonym: Hashenia, according to Chen et al. (1988, p.16); Circulodinium, 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) and Helby (1987, p.321–322) retained Circulodinium. Dörhöfer and Davies (1980, p.36) indicated that Cookson and Eisenack (1961a, p.72) provided an emendation for Canningia; however the latter authors did not formally emend the genus.
Type: Cookson and Eisenack, 1960b, pl.38, fig.1, as Canningia reticulata.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Cookson and Eisenack, 1960]:
Description:
Shell flattened, roughly four-sided to almost circular with a slight apical prominence and a broadly indented base. The basal projections (corresponding to antapical horns) are either equal or unequal and frequently differ slightly in shape. An equatorial girdle is either absent or faintly indicated both on the surface or by reentrant angles at the sides. The shell opens by a proximal break which results in the complete detachment of the apical region.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Evitt, 1978, p. 24
Synopsis: Cysts proximate, lenticular, with slight apical prominence and two antapical lobations; autophragm variously ornamented; ornamentation uniformly distributed, consisting of spines or processes of low to moderate relief; archeopyle apical, Type tA; parasulcal notch offset.
Description:
Shape: Lenticular; apical margin may be obtusely angular and antapical margin may have two subangular lobations.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Autophragm variously ornamented (scabrate to retirugulate), ornamentation uniformly distributed and of low to moderate relief; surface without spines or processes.
Paratabulation: Indicated by archeopyle only, or by archeopyle and paracingulum.
Archeopyle: Apical, Type tA; principal archeopyle suture zigzag with offset parasulcal notch; operculum free.
Paracingulum: Not indicated, or expressed faintly by small protrusions along the lateral margins at about midlength.
Parasulcus: Not indicated.
Size: Small to large.
Affinities:
Canningia differs from Cyclonephelium in being uniformly ornamented, whereas on Cyclonephelium the ornamentation is generally lacking or reduced in the midventral and middorsal areas. In addition, the ornamentation on Canningia tends to be less discrete and lower than on typical forms of Cyclonephelium. Canningia differs from Canninginopsis in lacking parasutural features.
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Emended descriptions:
Dörhöfer and Davies, 1980
Description:
Proximate dinoflagellate cyst with roughly five-sided to circular outline. Apex prominent, antapex broadly indented between two rounded antapical horns. Cingulum occasionally indicated by faint surface ornamentation and/or slight bulges representing postcingular horns. Surface smooth or with low but variable ornament. Archaeopyle (AI), formed along an asymmetrical zigzag suture line. Tabulation was not determined. Some species presently in Canningia do not exhibit the (AI) archaeopyle and are omitted from the genus. Their archaeopyle suture is symmetrical and the antapex founded.
----------------------------------------
Below, 1981: (Translation: LPP)
Diagnosis:
Spheroidal to lenticular cyst of round to pentagonal shape. Apex rounded or with low apical bulge. Antapex rounded, flattened or with lobus. Cyst wall two layered. Periphragm smooth or ornamented. Endocyst towards inner cyst smooth. Between both membranes variously structured ?endopragmal filling. Surface rarely divided in paraplates of gonyaulacoid scheme, usually undivided. Paracingulum and parasulcus into cyst indented or missing. Archeopyle apical, Type "Aa". Operculum simple, attached or enlarged.
------------
Remark: Hedlund and Norris, 1986, did not accept the emendation by Below, 1981.
----------------------------------------
Helby, 1987
Description:
Shape: Lenticular cyst, apicalmargin obtusely angular, antapical margin modified by two subangular, unequal lobes. Small lateral protrusions may mark paracingulum.
Wall features: Two layered, holocavate autophragm bearing processes varying in size, density and distribution, generally nontabular, less frequently penitabular or parasutural. Ectophragm usually reticulate, varying to rugoreticulate; occasionally, finely granulate or smooth.
Paratabulation: Indicated by archaeopyle and variably expressed parasutural features.
Archaeopyle: Apical, type (tA); principal archaeopyle suture zigzag with offset parasutural notch. Operculum usually free.
Paracingulum: Usually indicated by protrusion of parasutural ridges across dorsal surface, most evident at equator.
Parasulcus: Usually marked by absence or reduction in length of processes between wall layers. Where observed, parasulcus usually slightly sinuous moving from left ventral position on the epicyst to midventral position on the hypocyst.
Size: Small to large.
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Notes from Fensome et al., 2019a:
Synopsis. Areoligeracean cysts that are proximate, dorsoventrally compressed, lenticular, with asymmetrical to rounded antapex and a generally short apical prominence. Holocavate with generally narrow pericoel; the connections between endophragm and periphragm generally densely distributed and may be in linear (muri) or isolated elements (pillars). Periphragm continuous or discontinuous, generally smooth or with ornamentation of low relief. Archaeopyle apical, with formula A(1–4′); operculum free or attached; parasulcal notch offset to the left.
Remarks. Cookson and Eisenack (Citation1960, p. 251) provided the following description for Canningia:
Shell flattened, roughly five-sided to almost circular with a slight apical prominence and a broadly indented base. The basal projections (corresponding to antapical horns) are either equal or unequal and frequently differ slightly in shape. An equatorial girdle is either absent or faintly indicated both on the surface or by re-entrant angles at the sides. The shell opens by a proximal break which results in the complete detachment of the apical region.
Wall structure was clearly not considered an important feature of this genus at the outset. In contrast, as discussed above, we regard the wall structure to be a critical feature in distinguishing genera within the Cyclonephelium group, and define Canningia primarily on its holocavate wall structure.
Senoniasphaera is similar to Canningia in being cavate, but connecting structures are absent, sparse, or barely visible under the light microscope (see also discussion under Senoniasphaera). The pericoels are also generally broader in dorsoventral view in Senoniasphaera. In Renidinium, the walls are separated in mainly ventral marginal areas so that in apical view they project ventrally.
We consider the emendations of Canningia by Below (Citation1981) and Helby (1987) useful in developing our current concept of Canningia, but not that by Dörhöfer and Davies (Citation1980); see the introductory sections for a full discussion of the contributions of these authors. At present, the genus contains species with an overall holocavate structure (as in the type) and species in which the holocavation is restricted to the ambital periphery of the cyst. Separation of the latter group of species into their own genus might merit future consideration.
------------------------------------------------------------------------------------------------------------------------------------------------------
McLachlan et al., 2018:
Emended diagnosis. Areoligeracean cysts that are proximate to proximochorate, with subpentagonal to pentagonal ambitus. Typically, one apical, two lateral, and two antapical horns of varying development. Holocavate, usually with numerous nontabular to contabular processes connecting autophragm and ectophragm. Less frequently, processes penitabular or sutural. Processes varying in size, density, and distribution; disjunct, encircling, or predominantly marginate. Autophragm protrudes into horns formed by ectophragm. Ectophragm ornamentation of low relief; reticulate, rugoreticulate, finely granulate, or smooth. Cingulum indicated by sutural ridges across dorsal surface. Sulcus demarcated by absence or reduction in length of ectophragm support structures; slightly sinuous, tracing from left ventral position on the epicyst to midventral position of the hypocyst. Tabulation indicated by archaeopyle and sutural features. Archaeopyle apical, with formula A(1–4'), operculum free; sulcal notch offset to the left.
Comparison. Canningia differs from Senoniasphaera in being subpentagonal to pentagonal, bearing lateral horn autophragm protrusion, and in possessing a more extensive network of ectophragm support structures.
------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Canningia Cookson and Eisenack, 1960b, emend. Helby, 1987. According to Helby (1987, p.322), this species has a lenticular body, subpentagonal in outline, two-layered and with or without indications of paratabulation. The autophragm bears processes of variable size, which may be nontabular, less frequently penitabular or parasutural. The ectophragm is usually reticulate, varying to rugo-reticulate, occasionally finely granular or smooth.