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Occisucysta
From Williams et al., 2017:
[Occisucysta, Gitmez, 1970, p. 267; Emendation: Jan du Chêne et al., 1986b, p. 12-15
Tax. sr. syn. of Diacanthum Habib, 1972, according to Below, 1981. Lentin and Williams, 1981, retained Diacanthum as a separate genus.
Type species: Occisucysta balios, Gitmez, 1970 (pl.5, figs.1–2; text-fig.16)] ; emend. Jan du Chêne et al., 1986
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Original description: [Gitmez 1970]: (Translation: LPP):
Diagnosis:
Proximate dinoflagellate cysts, spherical, or broadly ovoidal, with the tabulation 4`, 0-1a, 6``, 6c, 6-7```, 1p, 0-1pv, 1````. Cingulum strongly or weakly helicoid; sulcus generally extending onto epitract. Strong apical horn present, median and antapical horns lacking. Sutures in form of high ridges, denticulate, fenestrate or spiny. Surface of the shell is granular or tuberculate. Precingular archaeopyle is normally present and forms by loss of two precingular plates (2`` and 3``).
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Modified description:
Stover and Evitt 1978, p. 176-177:
Synopsis:
Cysts proximochorate, subspherical, with a short apical horn; paratabulation gonyaulacacean, indicated by parasutural ridges or septa; archeopyle precingular, Type 2P; operculum compound.
Description:
Shape: Subspherical, with a short apical horn.
Wall relationships: Autophragm only.
Wall features: Parasutural ridges or septa smooth to faintly ornamented; crests spinate, denticulate or smooth. Autophragm between ridges or septa has scattered granulae, tuberculae, or is indistinctly ornamented.
Paratabulation: Indicated by parasutural features; gonyaulacacean, formula: 4`, 1a, 6``, 6c, 6```, 1p, 1````, 2-4s.
Archeopyle: Precingular, Type 2P, composed of paraplates 2`` + 3``; operculum free, compound.
Paracingulum: Indicated by six rectangular paraplates.
Parasulcus: Subdivided, longitudinally elongate area with two to four paraplates. Paraplate identified as 7``` is reinterpreted as occurring within the parasulcus.
Size: Intermediate.
Affinities:
Occisucysta differs from Diacanthum, which also has gonyaulacacean paratabulation expressed by parasutural features and an archeopyle 2P, in that its archeopyle forms through the release of paraplates 2`` + 3`` rather than 3`` + 4``.
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Emended description:
Jan du Chêne et al., 1986:
Diagnosis:
Proximate cyst, cornucavate or sometimes suturocavate, form subspherical to broadly ovoidal or polyhedrical, surmounted by an apical horn formed exclusively by the periphragm. Paratabulation gonyaulacoidal 2pr, 4`, 6``, 6c, 5s, 6```, 1p, 1````, indicated by low but continuous parasutural septa, with smooth or ornamented crests. Periphragm smooth or ornamented with patterns of faint relief. Archaeopyle type 2P (2``+3``). Operculum free, composite.
Description:
Form: Cyst proximate, ovoidal to subspherical, sometimes polyhedrical. It is surmounted by a prominent apical horn. In lateral or dorsoventral view, the outline of the cyst may appear angular, caused by presence of parasutural septa.
Cyst wall: The cyst wall consists of a distinct endophragm and periphragm. The periphragm is clearly detached from the the endophragm to solely form the apical horn. The periphragm may also be detached from the endophragm at the level of the paracingulum and the antapical area (cyst suturocavate).
Wall features:
Periphragm: Parasutural septa continuous, relatively low, with smooth or ornamented crests. Periphragm may be smooth or ornamented, the ornamentation remaining relatively low (cyst proximate).
Endophragm: generally smooth or granular, in certain species the endophragm may also posses ornamentation connecting it to the periphragm.
Paratabulation: indicated by the parasutural septa delimiting the paraplates: 2pr, 4`, 6``, 6c, 5s, 6```, 1p, 1````. Gonyaulacoid scheme with the following characteristics:
(A) At the level of the apical area, the first preapical paraplate, equivalent to paraplate P of the Taylor (1980) or Evitt (1985) system, is in contact with paraplate 3`, whilst the second preapical, Q of of Taylor or Evitt is not in contact with paraplate 2`.
(B) In the ventral area, the last precingular 6`` is in contact with the apicals 4` and 1`, whilst the sulcal as is in contact with the second postcingular 2```. Paraplate 1``` does not touch the paracingulum.
(C) At the level of the antapical area, paraplate 1````, situated on the axis of the cyst, is clearly asymmetrical, its right side being longer than its left side. This paraplate is in contact with six others: 3```, 4```, 5```, 6```, ps and 1p. The postcingular middorsal 4``` is situated approximately below the the precingular 3``. Paraplate 1p has six sides and is nearly as long as it is broad.
Archaeopyle: Precingular, formed by the loss of paraplates 2`` and 3``. Operculum free, composite. SEM studies of numerous specimens could not prove the presence of an endo- and peri-archaeopyle.
Paracingulum: It is generally well-indicated by parasutural septa, which may be very high in certain species, and is subdivided into six cingular paraplates.
Parasulcus: Oriented longitudinally, it corresponds with type L of Evitt (1985), and comprises five paraplates: as, ras, ls, rs, ps and a flagellar area. Paraplate 1``` is not in contact with the paracingulum and could be included in the sulcal paraplates.
Dimensions: Variable, length 45 to 100 µm.
Affinities:
Occisucysta differs from Diacanthum Habib, 1972; emend. Habib and Drugg, 1987 and from Tehemadinium Jan du Chêne et al., 1986, by the presence of a periphragm and an endophragm, clearly separated apically (cornucavate) and sometimes in the cingular and antapical areas (suturocavate), as well as in certain paratabulation details.
Diacanthum, Exiguisphaera and Tehemadinium have an autophragm only and consequently do not show any cavation.
Exiguisphaera has a 2P archaeopyle, corresponding with paraplates 3`` and 4``, whilst the archaeopyle of Occisucysta corresponds with paraplates 2`` and 3``, and that of Diacanthum can vary from P (3``) to 2P (2``+3``) or 3P (2``+3``+4``).
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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.
Occisucysta Gitmez, 1970, emend. Jan du Chêne et al., 1986b. From the emendation Jan du Chêne et al. (1986b, p.14), cyst proximate, cornucavate or sometimes suturocavate, subspherical to largely ovoidal or polyhedral, with an apical horn formed from the periphragm only. Paratabulation of the gonyaulacoid type 2pr, 4`, 6", 6c, 5s, 6``` , 1p, 1```` , emphasized by low but continuous parasutural septa that are smooth or ornamented. Periphragm smooth or ornamented with features of low relief. Archeopyle type 2P (2" + 3"). Operculum free, compound. According to Jan du Chêne et al. (1986b, p.21), Occisucysta differs from Tehamadinium in the presence of a differentiated periphragm, of a prominent apical horn formed from the periphragm only, and also in details of paratabulation. Sometimes, the periphragm and endophragm are also separated in the cingular area (suturocavate).
[Occisucysta, Gitmez, 1970, p. 267; Emendation: Jan du Chêne et al., 1986b, p. 12-15
Tax. sr. syn. of Diacanthum Habib, 1972, according to Below, 1981. Lentin and Williams, 1981, retained Diacanthum as a separate genus.
Type species: Occisucysta balios, Gitmez, 1970 (pl.5, figs.1–2; text-fig.16)] ; emend. Jan du Chêne et al., 1986
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Original description: [Gitmez 1970]: (Translation: LPP):
Diagnosis:
Proximate dinoflagellate cysts, spherical, or broadly ovoidal, with the tabulation 4`, 0-1a, 6``, 6c, 6-7```, 1p, 0-1pv, 1````. Cingulum strongly or weakly helicoid; sulcus generally extending onto epitract. Strong apical horn present, median and antapical horns lacking. Sutures in form of high ridges, denticulate, fenestrate or spiny. Surface of the shell is granular or tuberculate. Precingular archaeopyle is normally present and forms by loss of two precingular plates (2`` and 3``).
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Modified description:
Stover and Evitt 1978, p. 176-177:
Synopsis:
Cysts proximochorate, subspherical, with a short apical horn; paratabulation gonyaulacacean, indicated by parasutural ridges or septa; archeopyle precingular, Type 2P; operculum compound.
Description:
Shape: Subspherical, with a short apical horn.
Wall relationships: Autophragm only.
Wall features: Parasutural ridges or septa smooth to faintly ornamented; crests spinate, denticulate or smooth. Autophragm between ridges or septa has scattered granulae, tuberculae, or is indistinctly ornamented.
Paratabulation: Indicated by parasutural features; gonyaulacacean, formula: 4`, 1a, 6``, 6c, 6```, 1p, 1````, 2-4s.
Archeopyle: Precingular, Type 2P, composed of paraplates 2`` + 3``; operculum free, compound.
Paracingulum: Indicated by six rectangular paraplates.
Parasulcus: Subdivided, longitudinally elongate area with two to four paraplates. Paraplate identified as 7``` is reinterpreted as occurring within the parasulcus.
Size: Intermediate.
Affinities:
Occisucysta differs from Diacanthum, which also has gonyaulacacean paratabulation expressed by parasutural features and an archeopyle 2P, in that its archeopyle forms through the release of paraplates 2`` + 3`` rather than 3`` + 4``.
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Emended description:
Jan du Chêne et al., 1986:
Diagnosis:
Proximate cyst, cornucavate or sometimes suturocavate, form subspherical to broadly ovoidal or polyhedrical, surmounted by an apical horn formed exclusively by the periphragm. Paratabulation gonyaulacoidal 2pr, 4`, 6``, 6c, 5s, 6```, 1p, 1````, indicated by low but continuous parasutural septa, with smooth or ornamented crests. Periphragm smooth or ornamented with patterns of faint relief. Archaeopyle type 2P (2``+3``). Operculum free, composite.
Description:
Form: Cyst proximate, ovoidal to subspherical, sometimes polyhedrical. It is surmounted by a prominent apical horn. In lateral or dorsoventral view, the outline of the cyst may appear angular, caused by presence of parasutural septa.
Cyst wall: The cyst wall consists of a distinct endophragm and periphragm. The periphragm is clearly detached from the the endophragm to solely form the apical horn. The periphragm may also be detached from the endophragm at the level of the paracingulum and the antapical area (cyst suturocavate).
Wall features:
Periphragm: Parasutural septa continuous, relatively low, with smooth or ornamented crests. Periphragm may be smooth or ornamented, the ornamentation remaining relatively low (cyst proximate).
Endophragm: generally smooth or granular, in certain species the endophragm may also posses ornamentation connecting it to the periphragm.
Paratabulation: indicated by the parasutural septa delimiting the paraplates: 2pr, 4`, 6``, 6c, 5s, 6```, 1p, 1````. Gonyaulacoid scheme with the following characteristics:
(A) At the level of the apical area, the first preapical paraplate, equivalent to paraplate P of the Taylor (1980) or Evitt (1985) system, is in contact with paraplate 3`, whilst the second preapical, Q of of Taylor or Evitt is not in contact with paraplate 2`.
(B) In the ventral area, the last precingular 6`` is in contact with the apicals 4` and 1`, whilst the sulcal as is in contact with the second postcingular 2```. Paraplate 1``` does not touch the paracingulum.
(C) At the level of the antapical area, paraplate 1````, situated on the axis of the cyst, is clearly asymmetrical, its right side being longer than its left side. This paraplate is in contact with six others: 3```, 4```, 5```, 6```, ps and 1p. The postcingular middorsal 4``` is situated approximately below the the precingular 3``. Paraplate 1p has six sides and is nearly as long as it is broad.
Archaeopyle: Precingular, formed by the loss of paraplates 2`` and 3``. Operculum free, composite. SEM studies of numerous specimens could not prove the presence of an endo- and peri-archaeopyle.
Paracingulum: It is generally well-indicated by parasutural septa, which may be very high in certain species, and is subdivided into six cingular paraplates.
Parasulcus: Oriented longitudinally, it corresponds with type L of Evitt (1985), and comprises five paraplates: as, ras, ls, rs, ps and a flagellar area. Paraplate 1``` is not in contact with the paracingulum and could be included in the sulcal paraplates.
Dimensions: Variable, length 45 to 100 µm.
Affinities:
Occisucysta differs from Diacanthum Habib, 1972; emend. Habib and Drugg, 1987 and from Tehemadinium Jan du Chêne et al., 1986, by the presence of a periphragm and an endophragm, clearly separated apically (cornucavate) and sometimes in the cingular and antapical areas (suturocavate), as well as in certain paratabulation details.
Diacanthum, Exiguisphaera and Tehemadinium have an autophragm only and consequently do not show any cavation.
Exiguisphaera has a 2P archaeopyle, corresponding with paraplates 3`` and 4``, whilst the archaeopyle of Occisucysta corresponds with paraplates 2`` and 3``, and that of Diacanthum can vary from P (3``) to 2P (2``+3``) or 3P (2``+3``+4``).
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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.
Occisucysta Gitmez, 1970, emend. Jan du Chêne et al., 1986b. From the emendation Jan du Chêne et al. (1986b, p.14), cyst proximate, cornucavate or sometimes suturocavate, subspherical to largely ovoidal or polyhedral, with an apical horn formed from the periphragm only. Paratabulation of the gonyaulacoid type 2pr, 4`, 6", 6c, 5s, 6``` , 1p, 1```` , emphasized by low but continuous parasutural septa that are smooth or ornamented. Periphragm smooth or ornamented with features of low relief. Archeopyle type 2P (2" + 3"). Operculum free, compound. According to Jan du Chêne et al. (1986b, p.21), Occisucysta differs from Tehamadinium in the presence of a differentiated periphragm, of a prominent apical horn formed from the periphragm only, and also in details of paratabulation. Sometimes, the periphragm and endophragm are also separated in the cingular area (suturocavate).