Back
Cyclonephelium
From Williams et al., 2017:
[Cyclonephelium, Deflandre and Cookson, 1955, p. 285; Emendations: Cookson and Eisenack, 1962b, p. 493-494; Williams and Downie, 1966c, p. 223; Ioannides et al., 1977, p. 450; Sarjeant and Stover, 1978, p. 51; Stover and Evitt, 1978, p. 35-36; Dörhöfer and Davies, 1980, p. 41.
tax. sr. syn. of Circulodinium Alberti, 1961, according to Davey, 1978. Jansonius, 1986, and Helby, 1987, retained Circulodinium as a separate genus.
tax. sr. syn. of Tenua Eisenack, 1958, according to Sarjeant and Stover, 1978. Sarjeant, 1985, and Lentin and Williams, 1989, retained Tenua as a separate genus.
Type species: Cyclonephelium compactum, Deflandre and Cookson, 1955 (pl.2, fig.12)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: Deflandre and Cookson, 1955
Description:
Shell spheroidal, flattened, with an equatorial ornamentation that extends for varying distances from the equator but never to the poles. The ornament is composed of processes that are either distinct or close and confluent and sometimes connected by more or less broad trabeculae. Shell often provided with a large ill-defined lateral opening.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Cookson and Eisenack, 1962:
Description:
Shell nearly flat or apparently concavo-convex, circular to slightly oval in outline, the apex and/or antapex with or without a blunt prominence, the
antapex occasionally slightly indented. The ornament, which is restricted to a circumferential zone of varying width, is in the form of (1) processes, of varying lengths and shapes, which are distinct or more or less confluent, (2) thin membranes supported at intervals by strong processes, or (3) densely arranged surface thickenings. Sometimes the ornament is more strongly enveloped in the antapical region. The shell opens by the detachment of an apical segment along a nearly straight line.
------------------------------------------
Williams and Downie, 1966:
Description:
Chorate cysts with central body flattened dorso-ventrally and apparently concavo-convex, outline circular to slightly oval. Apex and/or antapex with or without blunt prominence, antapex occasionally slightly indented. Ornamentation restricted to circumferential zone of varying width, consisting of (1 ) processes, of varying lengths and shapes, distinct or more or less confluent, (2) thin membrane supported at intervals by strong processes, or (3) densely arranged surface thickenings. Ornamentation sometimes more strongly developed in antapical region. Archaeopyle apical tetratabular. Wall layers not distinguished.
------------------------------------------
Ioannides et al., 1977:
Diagnosis:
Proximate to chorate cysts with central body normally flattened dorsoventrally and apparently concavo-convex. Outline circular to oval. Apex or antapex with or without blunt prominence, antapex occasionally slightly indented. Ornament restricted to circumferential zone of varying width,
considerably varied in form, consisting of (1) processes, of varying lengths and shapes, distinct or more or less confluent; (2) thin membranous structures supported at intervals by strong processes; or (3) densely set surface thickenings. Ornament sometimes better developed in antapical region. Wall layers not observed. Archaeopyle apical, tetratabular.
------------------------------------------
Sarjeant and Stover, 1978:
Diagnosis:
Proximate to chorate cysts, normally flattened dorso-ventrally and apparently concavo-convex. Outline more or less circular to broadly oval and
commonly modified apically by a single medial prominence and/or antapically by a single asymmetrically situated prominence, or by two antapical prominences separated by a concavity. Wall, single-layered or consisting of two closely appressed layers, thin or of moderate thickness. Ornament concentrated in a circumferential zone of varying width or distributed unequally over the whole surface; the middorsal and midventral areas consistently have reduced ornamentation or entirely lack ornamentation.
The form of ornament is highly variable, at both the inter- and intraspecific levels. It includes (1) processes of varying lengths and shapes that may be isolated, linked distally by trabeculae, or confluent distally, proximally or at intermediate levels; (2) thin membraneous septa, supported at irregular intervals by thickenings; the septa may intersect to form imperfect reticula whose mesh varies in size and shape; and (3) densely arranged granulae, tuberculae, baculae or verrucae.
The archeopyle is apical, type A, with a zigzag principal suture; accessory archaeopyle sutures, where developed are typically quite short and correspond to the boundaries between precingular paraplates. The operculum is typically free but may be still attached. The arrangement of ornament sometimes gives indication of a paracingulum or of boundaries between some paraplates, but the paratabulation is generally not clearly indicated.
------------------------------------------
Stover and Evitt, 1978:
Synopsis:
Cysts proximochorate, lenticular; autophragm variously ornamented with numerous closely spaced features of low to moderate relief that may be spines or membranous septa; ornamentation generally reduced or lacking in midventral and middorsal areas; paratabulation rarely indicated by ornament; archeopyle apical, Type tA; parasulcal notch offset.
Description:
Shape: Lenticular; apical margin may be obtusely angular and antapical margin may have a shallow medial concavity.
Wall relationships: Autophragm only.
Wall features: Parasutural alignment of ornamentation generally faint, discontinuous, and confined to areas adjacent to paracingulum. Autophragm generally ornamented with numerous closely spaced features of low or moderate relief, including membranous septa or spines; latter may be interconnected distally. Ornamentation, regardless of type, generally lacking or reduced in midventral and middorsal areas, and elsewhere may be in penitabular rows.
Paratabulation: Indicated by archeopyle only, or occasionally by archeopyle and by the distribution of ornamentation in parasutural or penitabular rows.
Archeopyle: Apical, Type tA; transverse dimension greater than dorsal- ventral dimension; principal archeopyle suture zigzag with offset parasulcal notch; operculum free.
Paracingulum: Generally not indicated or indicated feebly by the transverse alignment of ornamentation.
Parasulcus: Not indicated.
Size: Intermediate to large.
Affinities:
Cyclonephelium differs from Canningia in having reduced ornamentation, or none at all, on the midventral and middorsal areas. In addition, the ornamentation on Cyclonephelium is typically more discrete (isolated) and higher than that on Canningia.
Glaphyrocysta has long processes, relative to body size, which are always connected distally. Processes on Cyclonephelium, in contrast, are short and rarely connected distally.
------------------------------------------
Dörhöfer and Davies, 1980:
Diagnosis:
Dorsoventrally flattened proximate dinoflagellate cysts. Outline symmetrical, subcircular to ovoidal, occasionally slightly asymmetrical. Apex often bulges out into a short blunt apical horn. No hypotractal horns present. Variable apteate ornament consisting of capitate spines or baculae which may or may not fuse distally and/or proximally. The intra- and penitabular ornament is pronounced in the circumferential area. In the ventral and dorsal areas the ornament is reduced or lacking. Tabulation formulae: 4`, 6``, 5-6c, 6```, 1p. 1````; archaeopyle (4A).
[Cyclonephelium, Deflandre and Cookson, 1955, p. 285; Emendations: Cookson and Eisenack, 1962b, p. 493-494; Williams and Downie, 1966c, p. 223; Ioannides et al., 1977, p. 450; Sarjeant and Stover, 1978, p. 51; Stover and Evitt, 1978, p. 35-36; Dörhöfer and Davies, 1980, p. 41.
tax. sr. syn. of Circulodinium Alberti, 1961, according to Davey, 1978. Jansonius, 1986, and Helby, 1987, retained Circulodinium as a separate genus.
tax. sr. syn. of Tenua Eisenack, 1958, according to Sarjeant and Stover, 1978. Sarjeant, 1985, and Lentin and Williams, 1989, retained Tenua as a separate genus.
Type species: Cyclonephelium compactum, Deflandre and Cookson, 1955 (pl.2, fig.12)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: Deflandre and Cookson, 1955
Description:
Shell spheroidal, flattened, with an equatorial ornamentation that extends for varying distances from the equator but never to the poles. The ornament is composed of processes that are either distinct or close and confluent and sometimes connected by more or less broad trabeculae. Shell often provided with a large ill-defined lateral opening.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Cookson and Eisenack, 1962:
Description:
Shell nearly flat or apparently concavo-convex, circular to slightly oval in outline, the apex and/or antapex with or without a blunt prominence, the
antapex occasionally slightly indented. The ornament, which is restricted to a circumferential zone of varying width, is in the form of (1) processes, of varying lengths and shapes, which are distinct or more or less confluent, (2) thin membranes supported at intervals by strong processes, or (3) densely arranged surface thickenings. Sometimes the ornament is more strongly enveloped in the antapical region. The shell opens by the detachment of an apical segment along a nearly straight line.
------------------------------------------
Williams and Downie, 1966:
Description:
Chorate cysts with central body flattened dorso-ventrally and apparently concavo-convex, outline circular to slightly oval. Apex and/or antapex with or without blunt prominence, antapex occasionally slightly indented. Ornamentation restricted to circumferential zone of varying width, consisting of (1 ) processes, of varying lengths and shapes, distinct or more or less confluent, (2) thin membrane supported at intervals by strong processes, or (3) densely arranged surface thickenings. Ornamentation sometimes more strongly developed in antapical region. Archaeopyle apical tetratabular. Wall layers not distinguished.
------------------------------------------
Ioannides et al., 1977:
Diagnosis:
Proximate to chorate cysts with central body normally flattened dorsoventrally and apparently concavo-convex. Outline circular to oval. Apex or antapex with or without blunt prominence, antapex occasionally slightly indented. Ornament restricted to circumferential zone of varying width,
considerably varied in form, consisting of (1) processes, of varying lengths and shapes, distinct or more or less confluent; (2) thin membranous structures supported at intervals by strong processes; or (3) densely set surface thickenings. Ornament sometimes better developed in antapical region. Wall layers not observed. Archaeopyle apical, tetratabular.
------------------------------------------
Sarjeant and Stover, 1978:
Diagnosis:
Proximate to chorate cysts, normally flattened dorso-ventrally and apparently concavo-convex. Outline more or less circular to broadly oval and
commonly modified apically by a single medial prominence and/or antapically by a single asymmetrically situated prominence, or by two antapical prominences separated by a concavity. Wall, single-layered or consisting of two closely appressed layers, thin or of moderate thickness. Ornament concentrated in a circumferential zone of varying width or distributed unequally over the whole surface; the middorsal and midventral areas consistently have reduced ornamentation or entirely lack ornamentation.
The form of ornament is highly variable, at both the inter- and intraspecific levels. It includes (1) processes of varying lengths and shapes that may be isolated, linked distally by trabeculae, or confluent distally, proximally or at intermediate levels; (2) thin membraneous septa, supported at irregular intervals by thickenings; the septa may intersect to form imperfect reticula whose mesh varies in size and shape; and (3) densely arranged granulae, tuberculae, baculae or verrucae.
The archeopyle is apical, type A, with a zigzag principal suture; accessory archaeopyle sutures, where developed are typically quite short and correspond to the boundaries between precingular paraplates. The operculum is typically free but may be still attached. The arrangement of ornament sometimes gives indication of a paracingulum or of boundaries between some paraplates, but the paratabulation is generally not clearly indicated.
------------------------------------------
Stover and Evitt, 1978:
Synopsis:
Cysts proximochorate, lenticular; autophragm variously ornamented with numerous closely spaced features of low to moderate relief that may be spines or membranous septa; ornamentation generally reduced or lacking in midventral and middorsal areas; paratabulation rarely indicated by ornament; archeopyle apical, Type tA; parasulcal notch offset.
Description:
Shape: Lenticular; apical margin may be obtusely angular and antapical margin may have a shallow medial concavity.
Wall relationships: Autophragm only.
Wall features: Parasutural alignment of ornamentation generally faint, discontinuous, and confined to areas adjacent to paracingulum. Autophragm generally ornamented with numerous closely spaced features of low or moderate relief, including membranous septa or spines; latter may be interconnected distally. Ornamentation, regardless of type, generally lacking or reduced in midventral and middorsal areas, and elsewhere may be in penitabular rows.
Paratabulation: Indicated by archeopyle only, or occasionally by archeopyle and by the distribution of ornamentation in parasutural or penitabular rows.
Archeopyle: Apical, Type tA; transverse dimension greater than dorsal- ventral dimension; principal archeopyle suture zigzag with offset parasulcal notch; operculum free.
Paracingulum: Generally not indicated or indicated feebly by the transverse alignment of ornamentation.
Parasulcus: Not indicated.
Size: Intermediate to large.
Affinities:
Cyclonephelium differs from Canningia in having reduced ornamentation, or none at all, on the midventral and middorsal areas. In addition, the ornamentation on Cyclonephelium is typically more discrete (isolated) and higher than that on Canningia.
Glaphyrocysta has long processes, relative to body size, which are always connected distally. Processes on Cyclonephelium, in contrast, are short and rarely connected distally.
------------------------------------------
Dörhöfer and Davies, 1980:
Diagnosis:
Dorsoventrally flattened proximate dinoflagellate cysts. Outline symmetrical, subcircular to ovoidal, occasionally slightly asymmetrical. Apex often bulges out into a short blunt apical horn. No hypotractal horns present. Variable apteate ornament consisting of capitate spines or baculae which may or may not fuse distally and/or proximally. The intra- and penitabular ornament is pronounced in the circumferential area. In the ventral and dorsal areas the ornament is reduced or lacking. Tabulation formulae: 4`, 6``, 5-6c, 6```, 1p. 1````; archaeopyle (4A).