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Diacanthum
From Williams et al., 2017:
[Diacanthum, Habib, 1972, p. 376; Emendation: Habib and Drugg, 1987, p. 762
Tax. jr. synonym of Occisucysta Gitmez, 1970, according to Below, 1981. Lentin and Williams, 1981, retained Diacanthum as a separate genus.
Type species: Diacanthum hollisteri, Habib, 1972 (pl. 9, fig.1)]; emend. Habib and Drugg, 1987
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Original description: [Habib, 1972]:
Description:
Spherical to subspherical proximate cysts without pronounced apical extensions. Tabulation obscured in many specimens. but appears to consist of the following minimum tabulation: 4`-5` or 6``-6c-6```-1?````. Plate boundaries delimited in well-preserved specimens by raised perforate crests. Archeopyle relatively large, precingular, and formed by two plates (2P). Ornamentation variable, in the form of spines, grana, and alveolae.
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Modified descriptions:
Stover and Evitt, 1978, p. 152:
Synopsis:
Cysts proximate, subspherical; paratabulation gonyaulacacean, indicated by ill-defined parasutural ridges; archeopyle precingular, Type 2P (3`` + 4``).
Description:
Shape: Subspherical.
Wall relationships: Autophragm only.
Wall features: Parasutural ridges low, perforate, complete or discontinuous; not clearly differentiated from nonparasutural ridges. Autophragm between parasutural ridges granulate, spinulate, and with isolated ridges like those in parasutural positions.
Paratabulation: Indicated imprecisely by parasutural ridges; gonyaulacacean, provisional formula: 4`, 5-6``, Xc, 6c, 6```, ?1````.
Paratabulation formula not firmly established because surface ornamentation tends to obscure plate boundaries.
Archeopyle: Precingular, Type 2P, composed of paraplates 3`` + 4``; operculum free.
Paracingulum: Indicated by an equatorially transverse, shallow, concave depression bordered by low parasutural ridges.
Parasulcus: Expression uncertain.
Size: Intermediate to large.
Affinities:
Diacanthum differs from Occisucysta, which also has a gonyaulacacean paratabulation expressed by parasutural features and a Type 2P archeopyle, in having the archeopyle formed through the release of paraplates3`` + 4`` rather than 2`` + 3``.
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Emended description:
Habib and Drugg, 1987
Description:
Spheroidal proximate autocysts compressed to a subcircular outline. Cyst tabulation sexiform gonyaulacoid with L-type ventral organization; tabulation indicated by narrow septal boundaries. Cyst wall perforate, and with intratabular spines which may form spinate ridges. Archeopyle precingular 2P(3``-4``); it may be variable in the precingular series, as in the type species, but must include examples which involve the third and fourth precingular plates, either as 2P(3``-4``), or within 3P(2``-3``-4``); limit of variability within a given species P(3``), 2P(2``-3``)/3``-4``), 3P(2``-3``-4``). Opercular pieces variable in number; they may remain partially attached (adnate or adherent) to the cyst, or detached; one or more detached pieces may remain closely associated with the cyst. Apical horn may be present or absent.
Affinities:
The concept of Diacanthum is emended to accommodate the variability of archeopyle development observed in the type species, The perforate wall structure is also considered to be diagnostic. It is distinguished from perforate species in Occisucysta Gitmez, 1969 and Cribroperidinium Neale and Sargeant, 1962, emended Helenes, 1984, both of which have sexiform gonyaulacoid tabulation and L-type ventral organization, by the nature of the archeopyle.
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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.
Diacanthum Habib, 1972, emend. Habib and Drugg, 1987. Diacanthum , according to Habib and Drugg (1987, p.762), has the L-type ventral organization and the tabulation indicated by narrow septal boundaries. Cyst wall perforate with intratabular spines which may form spinate ridges. Archeopyle precingular resulting from loss of plates 3", 3" + 2", 3" + 4" or plates 2 +3 + 4". Opercular pieces may be partly attached or detached.
[Diacanthum, Habib, 1972, p. 376; Emendation: Habib and Drugg, 1987, p. 762
Tax. jr. synonym of Occisucysta Gitmez, 1970, according to Below, 1981. Lentin and Williams, 1981, retained Diacanthum as a separate genus.
Type species: Diacanthum hollisteri, Habib, 1972 (pl. 9, fig.1)]; emend. Habib and Drugg, 1987
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Habib, 1972]:
Description:
Spherical to subspherical proximate cysts without pronounced apical extensions. Tabulation obscured in many specimens. but appears to consist of the following minimum tabulation: 4`-5` or 6``-6c-6```-1?````. Plate boundaries delimited in well-preserved specimens by raised perforate crests. Archeopyle relatively large, precingular, and formed by two plates (2P). Ornamentation variable, in the form of spines, grana, and alveolae.
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Modified descriptions:
Stover and Evitt, 1978, p. 152:
Synopsis:
Cysts proximate, subspherical; paratabulation gonyaulacacean, indicated by ill-defined parasutural ridges; archeopyle precingular, Type 2P (3`` + 4``).
Description:
Shape: Subspherical.
Wall relationships: Autophragm only.
Wall features: Parasutural ridges low, perforate, complete or discontinuous; not clearly differentiated from nonparasutural ridges. Autophragm between parasutural ridges granulate, spinulate, and with isolated ridges like those in parasutural positions.
Paratabulation: Indicated imprecisely by parasutural ridges; gonyaulacacean, provisional formula: 4`, 5-6``, Xc, 6c, 6```, ?1````.
Paratabulation formula not firmly established because surface ornamentation tends to obscure plate boundaries.
Archeopyle: Precingular, Type 2P, composed of paraplates 3`` + 4``; operculum free.
Paracingulum: Indicated by an equatorially transverse, shallow, concave depression bordered by low parasutural ridges.
Parasulcus: Expression uncertain.
Size: Intermediate to large.
Affinities:
Diacanthum differs from Occisucysta, which also has a gonyaulacacean paratabulation expressed by parasutural features and a Type 2P archeopyle, in having the archeopyle formed through the release of paraplates3`` + 4`` rather than 2`` + 3``.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Habib and Drugg, 1987
Description:
Spheroidal proximate autocysts compressed to a subcircular outline. Cyst tabulation sexiform gonyaulacoid with L-type ventral organization; tabulation indicated by narrow septal boundaries. Cyst wall perforate, and with intratabular spines which may form spinate ridges. Archeopyle precingular 2P(3``-4``); it may be variable in the precingular series, as in the type species, but must include examples which involve the third and fourth precingular plates, either as 2P(3``-4``), or within 3P(2``-3``-4``); limit of variability within a given species P(3``), 2P(2``-3``)/3``-4``), 3P(2``-3``-4``). Opercular pieces variable in number; they may remain partially attached (adnate or adherent) to the cyst, or detached; one or more detached pieces may remain closely associated with the cyst. Apical horn may be present or absent.
Affinities:
The concept of Diacanthum is emended to accommodate the variability of archeopyle development observed in the type species, The perforate wall structure is also considered to be diagnostic. It is distinguished from perforate species in Occisucysta Gitmez, 1969 and Cribroperidinium Neale and Sargeant, 1962, emended Helenes, 1984, both of which have sexiform gonyaulacoid tabulation and L-type ventral organization, by the nature of the archeopyle.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Diacanthum Habib, 1972, emend. Habib and Drugg, 1987. Diacanthum , according to Habib and Drugg (1987, p.762), has the L-type ventral organization and the tabulation indicated by narrow septal boundaries. Cyst wall perforate with intratabular spines which may form spinate ridges. Archeopyle precingular resulting from loss of plates 3", 3" + 2", 3" + 4" or plates 2 +3 + 4". Opercular pieces may be partly attached or detached.