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Chytroeisphaeridia
From Williams et al., 2017:
[Chytroeisphaeridia, (Sarjeant, 1962a, p.492) Downie and Sarjeant, 1965, p.102. Emendations: Pocock, 1972, p.99–100 and Davey, 1979d, p.211, both as Chytroeisphaeridia.
Type species: originally as Leiosphaeridia subgenus Chytroeisphaeridia chytroeides, Sarjeant, 1962a (pl.70, fig.13)] ; Chytroeisphaeridia chytroeides, Downie and Sarjeant, 1965; emend. Davey, 1979
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Original description Leiosphaeridia subgenus Chytroeisphaeridia: [Sarjeant, 1962]:
Diagnosis:
A subgenus of Leiosphaeridia comprising species having a polygonal or subpolygonal pylome, lateral or terminal in position. The pylome may not be present in all individuals of such species.
Remark: Downie et al., 1963, p. 9
Since the genus Leiosphaeridia is regarded by Wall (1962) as polyphyletic and no criteria are at present available for distinguishing the different biological groupings within it, the genus is for the present best treated as an acritarch.
It is here proposed that the subgenus Chytroeisphaeridia Sarjeant 1962, whose dinoflagellate affinity is demonstrated by the presence of an apical archaeopyle, should be elevated to generic status and transferred to the Dinophyceae, although the problems of distinguishnig its representatives from Leiosphaeridia in absence of an open archaeopyle are fully recognized.
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Emended descriptions:
Norris and Sarjeant, 1965:
Diagnosis:
Shell spherical to oval, without processes. Shell surface smooth, granular or punctate. Polygonal or subpolygonal apical archaeopyle.
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Pocock, 1972:
Diagnosis:
Vesicle subspherical or, more frequently, ovoid (outline circular to oval). Wall single-layered, usually relatively thin: smooth or carrying relatively subdued granulose or papillate ornament: vesicle may, or may not, show traces of polygonal plating (some individuals in a species may show
traces of plating, some may not); shield-shaped or polygonal aperture which may be closed by an operculum present in most species. Members of
this genus frequently contain yellow-green punctate bodies within the vesicle.
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Davey, 1979
Diagnosis:
The cysts are spherical to ovoidal in shape and are composed of a smooth, hyaline (unstructured) wall which is apparently single layered (autophragm). A hollow apical protuberance may be present; lateral and antapical structures are absent. The archaeopyle is formed by the loss of a single precingular paraplate (presumably 3``); the operculum may remain attached along its apical side. Additional obvious signs of a paratabulation are absent.
Affinities:
The type species of Tapeinosphaeridium, T. pericompsum loannides et al., 1977, is described as having a smooth, unstructured wall and a simple precingular archaeopyle. These characteristics indicate that it should be attributed to Chytroeisphaeridia as here defined and this transference hence makes Tapeinosphaeridium a junior synonym of Chytroeisphaeridia.
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Modified description:
Stover and Evitt, 1978, p. 28-29:
Synopsis:
Cysts subspherical and without ridges, septa, spines, or processes; autophragm smooth, scabrate or punctate; archeopyle apical, Type tA; other indications of paratabulation lacking.
Description:
Shape: Subspherical.
Wall relationships. Autophragm only.
Wall features. No parasutural features. Autophragm smooth, scabrate or punctate.
Paratabulation: Indicated by archeopyle only.
Archeopyle: Apical, Type tA; principal archeopyle suture faintly angular to zigzag; operculum free. (See also S&E`s comment under affinities.)
Paracingulum: Not indicated.
Parasulcus: Not indicated.
Size: Small to intermediate.
Remarks:
The emendation by Pocock (1972) of Chytroeisphaeridia, as well as his species description and illustrations, indicate clearly that under his concept species with either precingular or apical archeopyles would be included in the genus. At the 10th annual AASP Meeting, Davey demonstrated rather convincingly that the type species of Chytroeisphaeridia, C. chytroeides, possesses a precingular instead of an apical archeopyle. Consequently, other species now placed in the genus, together with those in Tapeinosphaeridium, which becomes a junior synonym of Chytroeisphaeridia, require evaluation and possibly reassignment depending upon Davey`s interpretation and revised description of Chytroeisphaeridia. Rather than to anticipate, perhaps incorrectly, the changes he may propose, we chose to retain both genera for the time being.
Affinities:
Chytroeisphaeridia differs from Batiacasphaera in having a smooth, scabrate, or punctate autophragm rather than an autophragm ornamented with low, isolated, or fused projections. Retention of both Chytroeisphaeridia and Batiacasphaera may be unrealistic unless smooth or punctate forms only are included in the former, and those with ornamentation features of low relief are assigned to Batiacasphaera.
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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.
Chytroeisphaeridia (Sarjeant, 1962a) Downie and Sarjeant, 1965 emend. Davey, 1979d. According to Davey (1979d), the cysts are spherical to ovoidal in shape and are composed of a smooth hyaline, unstructured wall which is apparently a single layer (autophragm). A hollow apical protuberance may be present. Lateral and antapical structures are absent. The archeopyle is formed from the loss of 3", the operculum may remain attached along the anterior margin. No other signs of tabulation.
[Chytroeisphaeridia, (Sarjeant, 1962a, p.492) Downie and Sarjeant, 1965, p.102. Emendations: Pocock, 1972, p.99–100 and Davey, 1979d, p.211, both as Chytroeisphaeridia.
Type species: originally as Leiosphaeridia subgenus Chytroeisphaeridia chytroeides, Sarjeant, 1962a (pl.70, fig.13)] ; Chytroeisphaeridia chytroeides, Downie and Sarjeant, 1965; emend. Davey, 1979
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Original description Leiosphaeridia subgenus Chytroeisphaeridia: [Sarjeant, 1962]:
Diagnosis:
A subgenus of Leiosphaeridia comprising species having a polygonal or subpolygonal pylome, lateral or terminal in position. The pylome may not be present in all individuals of such species.
Remark: Downie et al., 1963, p. 9
Since the genus Leiosphaeridia is regarded by Wall (1962) as polyphyletic and no criteria are at present available for distinguishing the different biological groupings within it, the genus is for the present best treated as an acritarch.
It is here proposed that the subgenus Chytroeisphaeridia Sarjeant 1962, whose dinoflagellate affinity is demonstrated by the presence of an apical archaeopyle, should be elevated to generic status and transferred to the Dinophyceae, although the problems of distinguishnig its representatives from Leiosphaeridia in absence of an open archaeopyle are fully recognized.
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Emended descriptions:
Norris and Sarjeant, 1965:
Diagnosis:
Shell spherical to oval, without processes. Shell surface smooth, granular or punctate. Polygonal or subpolygonal apical archaeopyle.
----------------------------------
Pocock, 1972:
Diagnosis:
Vesicle subspherical or, more frequently, ovoid (outline circular to oval). Wall single-layered, usually relatively thin: smooth or carrying relatively subdued granulose or papillate ornament: vesicle may, or may not, show traces of polygonal plating (some individuals in a species may show
traces of plating, some may not); shield-shaped or polygonal aperture which may be closed by an operculum present in most species. Members of
this genus frequently contain yellow-green punctate bodies within the vesicle.
----------------------------------
Davey, 1979
Diagnosis:
The cysts are spherical to ovoidal in shape and are composed of a smooth, hyaline (unstructured) wall which is apparently single layered (autophragm). A hollow apical protuberance may be present; lateral and antapical structures are absent. The archaeopyle is formed by the loss of a single precingular paraplate (presumably 3``); the operculum may remain attached along its apical side. Additional obvious signs of a paratabulation are absent.
Affinities:
The type species of Tapeinosphaeridium, T. pericompsum loannides et al., 1977, is described as having a smooth, unstructured wall and a simple precingular archaeopyle. These characteristics indicate that it should be attributed to Chytroeisphaeridia as here defined and this transference hence makes Tapeinosphaeridium a junior synonym of Chytroeisphaeridia.
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Modified description:
Stover and Evitt, 1978, p. 28-29:
Synopsis:
Cysts subspherical and without ridges, septa, spines, or processes; autophragm smooth, scabrate or punctate; archeopyle apical, Type tA; other indications of paratabulation lacking.
Description:
Shape: Subspherical.
Wall relationships. Autophragm only.
Wall features. No parasutural features. Autophragm smooth, scabrate or punctate.
Paratabulation: Indicated by archeopyle only.
Archeopyle: Apical, Type tA; principal archeopyle suture faintly angular to zigzag; operculum free. (See also S&E`s comment under affinities.)
Paracingulum: Not indicated.
Parasulcus: Not indicated.
Size: Small to intermediate.
Remarks:
The emendation by Pocock (1972) of Chytroeisphaeridia, as well as his species description and illustrations, indicate clearly that under his concept species with either precingular or apical archeopyles would be included in the genus. At the 10th annual AASP Meeting, Davey demonstrated rather convincingly that the type species of Chytroeisphaeridia, C. chytroeides, possesses a precingular instead of an apical archeopyle. Consequently, other species now placed in the genus, together with those in Tapeinosphaeridium, which becomes a junior synonym of Chytroeisphaeridia, require evaluation and possibly reassignment depending upon Davey`s interpretation and revised description of Chytroeisphaeridia. Rather than to anticipate, perhaps incorrectly, the changes he may propose, we chose to retain both genera for the time being.
Affinities:
Chytroeisphaeridia differs from Batiacasphaera in having a smooth, scabrate, or punctate autophragm rather than an autophragm ornamented with low, isolated, or fused projections. Retention of both Chytroeisphaeridia and Batiacasphaera may be unrealistic unless smooth or punctate forms only are included in the former, and those with ornamentation features of low relief are assigned to Batiacasphaera.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Chytroeisphaeridia (Sarjeant, 1962a) Downie and Sarjeant, 1965 emend. Davey, 1979d. According to Davey (1979d), the cysts are spherical to ovoidal in shape and are composed of a smooth hyaline, unstructured wall which is apparently a single layer (autophragm). A hollow apical protuberance may be present. Lateral and antapical structures are absent. The archeopyle is formed from the loss of 3", the operculum may remain attached along the anterior margin. No other signs of tabulation.