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Invertocysta
From Williams et al., 2017:
[Invertocysta, Edwards, 1984, p. 585
Type species: Invertocysta tabulata, Edwards, 1984 (pl.3, figs.3A–B; text-figs.6A–B)]
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Original description: [Edwards, 1984]:
Diagnosis:
Cyst cavate; endocyst ovoidal to ellipsoidal, often with a short apical boss. Pericyst discoidal or bowl-shaped, meridionally placed, open towards dorsal side.
Endophragm and periphragm appressed midventrally, periphragm extended outward elsewhere. Wall surface smooth except for parasutural ridges or thickenings of the periphragm indicating paratabulation.
Paratabulation gonyaulacacean, 4`, 6``, 4-5c, 5-6```, 1p, 1````, ?3-5s for Invertocysta tabulate, probably similar formula for I. lacrimosa but incompletely compressed.
Archeopyle precingular, type P, 3`` only.
Distribution of periphragmal paraplates asymmetrical such that most or all of the dorsal surface presents 3``, and is absent, and the dorsal part of the paracingulum is displaced towards the antapex. Up to five small paraplates may be distinguished in the parasulcal region.
Affinities:
In the genus Invertocysta, the bowl- or saucer-shaped periphragm opens to the dorsal side and is appressed to the endophragm midventrally. In Thalassiphora, the "bowl" of the periphragm opens ventrally and is attached middorsally. Stephodinium has a periphragmal extension which is positioned equatorially, rather than meridionally as in Invertocysta. Hystrichostrochylon has gonal processes and the wall layers are appressed middorsally. Invertocysta is probably related to Amiculosphaera, although in Amiculosphaera, the periphragm is appressed to the endophragm over most of the hypocyst.
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Modified description:
Stover and Williams, 1987, p. 129:
Synopsis:
Cysts proximate, outline more or less circular in dorsal-ventral view, circumcavate; endocyst ovoidal to ellipsoidal, pericyst bowl-shaped, open dorsally and appressed to endocyst midventrally; low parasutural features indicate a partial to nearly complete gonyaulacacean paratabulation with a formula of: 4`, 6``, 4-6c, 5-6```, 1p, 1````, ?3-5s; all or most of dorsal surface represented by paraplate 3``; archeopyle precingular, type P, 3`` only.
Description:
Shape: Pericyst outline in dorsal-ventral view more or less circular.
Wall relationships: Cysts circumcavate, endocyst ovoidal to ellipsoidal; pericyst bowl-shaped, open dorsally and attached to endocyst midventrally.
Wall features: Low parasutural ridges or thickenings of the periphragm indicate partial to nearly complete paratabulation.
Archeopyle: Precingular, ype P, 3`` only, operculum free.
Paratabulation: Gonyaulacacean, formula for complete or nearly complete paratabulation: 4`, 6``, 4-6c, 5-6```, 1p, 1````, ?3-5s.
Paracingulum: Not indicated, or expressed by 4 to 6 rectangular paraplates.
Parasulcus: Not indicated, or expressed by 3 or more paraplates.
Size: Intermediate to large, diameter 60 µm to 113 µm.
Affinities:
As stated by Edwards (1984, p. 585), "In the genus Invertocysta, the bowl- or saucer-shaped periphragm opens towards the dorsal side and is appressed to the endophragm midventrally. In Thalassiphora the `bowl` of the periphragm opens ventrally and is attached middorsally".
The periphragmal extension on Stephodinium Deflandre 1936 emended Davey 1970, is equatorial, rather than mainly dorsal. Amiculosphaera Harland 1979, differs from Invertocysta in having the periphragm and the endophragm appressed in the antapical area only and in possessing a funnel-shaped apical structure.
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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.
Invertocysta Edwards, 1984. Synopsis, from Stover and Williams (1987, p.129), cysts proximate, outline more or less circular in dorsal-ventral view, circumcavate; endocyst ovoidal to ellipsoidal, pericyst bowl-shaped, open dorsally and appressed to endocyst mid-ventrally; low parasutural features indicate a partial to nearly complete gonyaulacacean paratabulation with a formula of 4`, 6", 4-6c, 5-6"'. 1p, 1"" , 3-5s; all or most of dorsal surface represented by paraplate 3", archeopyle precingular, type P, 3" only.
[Invertocysta, Edwards, 1984, p. 585
Type species: Invertocysta tabulata, Edwards, 1984 (pl.3, figs.3A–B; text-figs.6A–B)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Edwards, 1984]:
Diagnosis:
Cyst cavate; endocyst ovoidal to ellipsoidal, often with a short apical boss. Pericyst discoidal or bowl-shaped, meridionally placed, open towards dorsal side.
Endophragm and periphragm appressed midventrally, periphragm extended outward elsewhere. Wall surface smooth except for parasutural ridges or thickenings of the periphragm indicating paratabulation.
Paratabulation gonyaulacacean, 4`, 6``, 4-5c, 5-6```, 1p, 1````, ?3-5s for Invertocysta tabulate, probably similar formula for I. lacrimosa but incompletely compressed.
Archeopyle precingular, type P, 3`` only.
Distribution of periphragmal paraplates asymmetrical such that most or all of the dorsal surface presents 3``, and is absent, and the dorsal part of the paracingulum is displaced towards the antapex. Up to five small paraplates may be distinguished in the parasulcal region.
Affinities:
In the genus Invertocysta, the bowl- or saucer-shaped periphragm opens to the dorsal side and is appressed to the endophragm midventrally. In Thalassiphora, the "bowl" of the periphragm opens ventrally and is attached middorsally. Stephodinium has a periphragmal extension which is positioned equatorially, rather than meridionally as in Invertocysta. Hystrichostrochylon has gonal processes and the wall layers are appressed middorsally. Invertocysta is probably related to Amiculosphaera, although in Amiculosphaera, the periphragm is appressed to the endophragm over most of the hypocyst.
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Modified description:
Stover and Williams, 1987, p. 129:
Synopsis:
Cysts proximate, outline more or less circular in dorsal-ventral view, circumcavate; endocyst ovoidal to ellipsoidal, pericyst bowl-shaped, open dorsally and appressed to endocyst midventrally; low parasutural features indicate a partial to nearly complete gonyaulacacean paratabulation with a formula of: 4`, 6``, 4-6c, 5-6```, 1p, 1````, ?3-5s; all or most of dorsal surface represented by paraplate 3``; archeopyle precingular, type P, 3`` only.
Description:
Shape: Pericyst outline in dorsal-ventral view more or less circular.
Wall relationships: Cysts circumcavate, endocyst ovoidal to ellipsoidal; pericyst bowl-shaped, open dorsally and attached to endocyst midventrally.
Wall features: Low parasutural ridges or thickenings of the periphragm indicate partial to nearly complete paratabulation.
Archeopyle: Precingular, ype P, 3`` only, operculum free.
Paratabulation: Gonyaulacacean, formula for complete or nearly complete paratabulation: 4`, 6``, 4-6c, 5-6```, 1p, 1````, ?3-5s.
Paracingulum: Not indicated, or expressed by 4 to 6 rectangular paraplates.
Parasulcus: Not indicated, or expressed by 3 or more paraplates.
Size: Intermediate to large, diameter 60 µm to 113 µm.
Affinities:
As stated by Edwards (1984, p. 585), "In the genus Invertocysta, the bowl- or saucer-shaped periphragm opens towards the dorsal side and is appressed to the endophragm midventrally. In Thalassiphora the `bowl` of the periphragm opens ventrally and is attached middorsally".
The periphragmal extension on Stephodinium Deflandre 1936 emended Davey 1970, is equatorial, rather than mainly dorsal. Amiculosphaera Harland 1979, differs from Invertocysta in having the periphragm and the endophragm appressed in the antapical area only and in possessing a funnel-shaped apical structure.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Invertocysta Edwards, 1984. Synopsis, from Stover and Williams (1987, p.129), cysts proximate, outline more or less circular in dorsal-ventral view, circumcavate; endocyst ovoidal to ellipsoidal, pericyst bowl-shaped, open dorsally and appressed to endocyst mid-ventrally; low parasutural features indicate a partial to nearly complete gonyaulacacean paratabulation with a formula of 4`, 6", 4-6c, 5-6"'. 1p, 1"" , 3-5s; all or most of dorsal surface represented by paraplate 3", archeopyle precingular, type P, 3" only.