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Morkallacysta
From Fensome et al., 2019:
Morkallacysta, Harris, 1974, p.163.
Taxonomic senior synonym: Palaeoperidinium, according to Lentin and Williams (1976, p.160) -- however Stover and Evitt (1978, p.113–114) retained Morkallacysta.
Type: Harris, 1974, pl.1, fig.5, as Morkallacysta pyramidalis.
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Original description: [Harris, 1974]:
Description:
Non-cavate dinoflagellate cysts of strongly peridinioid form with prominent apical and antapical horns. Helicoid girdle strongly marked. Archeopyle triangular with attached operculum. Cysts lacking tabulation and ornament.
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Modified description:
Stover and Evitt, 1978, p. 113:
Synopsis:
Cysts proximate, compressed peridinioid; apical and antapical horns prominent; autophragm commonly folded; indications of paratabulation weakly developed. Archeopyle apparently intercalary; Type uncertain, probably Type I, possibly 3I.
Description:
Shape: Compressed peridinioid; apical and antapical horns prominent.
Wall Relationships: Autophragm only.
Wall Features: Autophragm smooth to scabrate.
Paratabulation: Indicated mainly by paracingulum and archeopyle; almost always obscured because of folding.
Archeopyle: Probably intercalary; type uncertain, probably Type I, possibly 3I.
Paracingulum: Indicated by low, parallel, transverse ridges delimiting a shallow concavity.
Parasulcus: Not indicated or weakly expressed as a shallow depression on the hypocyst.
Size: Intermediate.
Affinities:
Morkallacysta differs from Deflandrea in having an autophragm only, rather than an endophragm and periphragm, and from Lejeunia in having well-developed apical and antapical horns.
Morkallacysta, Harris, 1974, p.163.
Taxonomic senior synonym: Palaeoperidinium, according to Lentin and Williams (1976, p.160) -- however Stover and Evitt (1978, p.113–114) retained Morkallacysta.
Type: Harris, 1974, pl.1, fig.5, as Morkallacysta pyramidalis.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Harris, 1974]:
Description:
Non-cavate dinoflagellate cysts of strongly peridinioid form with prominent apical and antapical horns. Helicoid girdle strongly marked. Archeopyle triangular with attached operculum. Cysts lacking tabulation and ornament.
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Modified description:
Stover and Evitt, 1978, p. 113:
Synopsis:
Cysts proximate, compressed peridinioid; apical and antapical horns prominent; autophragm commonly folded; indications of paratabulation weakly developed. Archeopyle apparently intercalary; Type uncertain, probably Type I, possibly 3I.
Description:
Shape: Compressed peridinioid; apical and antapical horns prominent.
Wall Relationships: Autophragm only.
Wall Features: Autophragm smooth to scabrate.
Paratabulation: Indicated mainly by paracingulum and archeopyle; almost always obscured because of folding.
Archeopyle: Probably intercalary; type uncertain, probably Type I, possibly 3I.
Paracingulum: Indicated by low, parallel, transverse ridges delimiting a shallow concavity.
Parasulcus: Not indicated or weakly expressed as a shallow depression on the hypocyst.
Size: Intermediate.
Affinities:
Morkallacysta differs from Deflandrea in having an autophragm only, rather than an endophragm and periphragm, and from Lejeunia in having well-developed apical and antapical horns.