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Rhynchodiniopsis
From Williams et al., 2017:
[Rhynchodiniopsis, Deflandre, 1935, p. 231; Emendations: Below, 1981a, p. 117; Sarjeant, 1982b, p. 34–35; Jan du Chêne et al., 1985b, p. 116, 118, 120.
Tax. jr. syn.: Gonyaulacysta, by implication in Millioud (1969, p.428), who illegitimately transferred the "type species" of Rhynchodiniopsis, Rhynchodiniopsis aptiana, to the junior name Gonyaulacysta — however, Lentin and Williams (1973, p.58,121) retained Gonyaulacysta.
Type species: Rhynchodiniopsis aptiana, Deflandre, 1935 (pl.5, fig.10; pl.8, figs.7–9)] ; emend. Sarjeant, 1982
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Original description: [Deflandre, 1935]: (Translation: Stover and Evitt, 1978, p. 184):
Diagnosis:
Rhynchodiniopsis aptiana n.g. n.sp. strongly resembles Palaeoperidinium at first glance. Its reticulate membrane is equally similar to that of recent Peridinium. Its tabulation, which is already partially known to me, its appendices arising from a plate, its furrow ornamented from place to place with curved spines, oppose its complete assimilation into an already described genus. Certain of its characters seem to me compare with those of Hystrichosphaera (cf. infra).
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Supplemental description:
Deflandre 1936, p. 180:
Diagnosis: The most important features of Rhynchodiniopsis are: 1. a stout hollow horn at its apex, which is truncate like a snout and appears to rise from an apical plate; 2. long curved spines found at the base of the plate sutures, completely ringing the cingulum; and 3. very strong development of aliform denticulae crests, which follow all the plate sutures and border the cingulum.
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Modified description:
Stover and Evitt, 1978, p. 184:
Synopsis:
Cysts subspherical to subpolyhedral, with an apical horn; autophragm scabrate to finely reticulate; paratabulation gonyaulacacean, indicated by parasutural ridges surmounted by fine, closely spaced spinules with prominent spines at major gonal positions; archaeopyle precingular, type P.
Description:
Shape: Subspherical to subpolyhedral, with an apical horn and rounded to truncate antapical margin.
Wall relationships: Autohragm only.
Wall features: Parasutural ridges low; crests surmounted by short, numerous, slender, closely spaced spinules or spines, and supplemented by longer gonal spines, especially along the paracingulum.
Paratabulation: indicated by parasutural ridges; gonyalacacean, formula: 3-4`, 1a, 6``, 6c?, 6```, 1p, 1````. A rectangular anterior intercalary paraplate lies between 3` and the anterior right side of 3``.
Archaeopyle: Precingular, Type P (3`` only); operculum free.
Paracingulum: Indicated by six (?) subrectangular paraplates.
Parasulcus: Delimited by parasutural features and apparently undivided.
Size: Intermediate.
Affinities:
Rhynchodiniopsis differs from Gonyaulacysta in having an autophragm (either a single wall layer or two appressed and virtually indistinguishable layers); it herefore lacks cavation, which is present in Gonyaulacysta. On Rhynchodiniopsis the spinules in the gonal positions, especially along the paracingulum, are noticeably longer than those in nongonal positions, whereas on Gonyaulacysta the denticles or spinules tend to be reduced or absent at and occasionally adjacent to the junctions of parasutural features.
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Emended descriptions:
Below, 1981: (Translations: Jan du Chêne et al., 1985: LPP)
Diagnosis:
Proximate cyst of spheroidal, ovoidal or polygonal outline, and with outstanding apical horn. Single-layered or bi-layered, but acavate. Paratabulation gonyaulacoidal: 102PR, 4`, 1-2a, 6``, Xc, 6```, 1pc, 1````, Xc (should be Xs). Of these, the preapical paraplates 1PR ans 2PR, as well as the dorsal intercalary, which is situated between 3`, 3`` and 4``, are of special importance. Parasutures indicated by ridges, surmounted by spines, thorns or distally branched appendices. Gonal spines can dominate in length compared to the parasutural spines. Paracingulum weakly spiral, parasulcus subdivided in as, ra, rs, ls, 1ps, but also often as broad, undifferentiated zones.
Archaeopyle precingular, P(3``). Operculum, compared to the size of paraplate 3``, often reduced.
-- rejected by Lentin and Williams, 1981, p. 244, without reasons given
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Sarjeant, 1982:
Diagnosis:
Proximate to proximochorate dinoflagellate cyst typically of small to intermediate, rarely of large size. Ambitus ovoidal to broadly ellipsoidal or subpolygonal, consistently with an apical horn or prominence and with parasutural crests of variable form. Development of cavation at the apex consistent; acrocavate to cornucavate or, to a restricted degree, epicavate, the supplementary cavation (Where developed) being in the form of a broad base to, or small plinth for, the horn but never more extensive. Antapical and lateral cavations lacking.
Paratabulation 0-2pa, 3-4`, 1-2a, 6``, 6c, 6```, 1p, 0-1pv, 1````; the sulcus may also show subdivision into paraplates. Paraplate 4` is quite large and roughly quadrate, having a moderately long boundary with a reduced 6``. The boundary between 4` and 6`` intersects with the right lateral boundary of 1` in a position anterior to, or almost at the level of, the junction of the latter paraplate with the sulcus. Cingulum strongly or weakly helicoid; between its two ends, the sulcus is typically straight. Crests on parasutures smooth, serrate or variably developed into denticles or spines of regular or irregular length and character: accessory crests feebly developed or (typically) lacking. Height of crests variable, but always less than 1/4 of the cyst width. Gonal spines of small to moderate height, present or absent. Surface of cyst smooth, granular, nodose, punctate or reticulate.
Archaeopyle single-plate precingular, formed by loss of paraplate 3``; operculum reduced.
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Jan du Chêne et al., 1985:
Diagnosis:
Proximate to proximochorate dinoflagellate cyst, acavate or sometimes slightly cornucavate, body subspherical or polyhedrical, with an apical horn. Wall formed by autophragm, or appressed periphragm and endophragm. The parasutural septa are distinct, often high, sometimes perforate, with spinous crests. These spines can sometimes be relatively long, simple or distally split. The intratabular areas are smooth to finely ornamented.
The paratabulation is clearly indicated by parasutural septa: 2pr, 4`, 0-2a, 6``, 6c, 6```, 1p, 1````, xs. Ventrally, paraplate 6`` is typically pentagonal, in contact with 1` and 4`, the latter of which does not touch the sulcal area. Antapical paraplate 1```` is slightly asymmetrical. At the apex, paraplates 2` and 4` are separated by the preapicals.
The archaeopyle is precingular, type P(3``), with a free operculum.
Affinities:
Rhynchodiniopsis differs from Acanthaulax in the absence of ornamentation on the intratabular areas. Cribroperidinium is sometimes characterized by the presence of accessory septa and especially by certain aspects of paratabulation (Helenes, 1984, p. 116-117).
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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.
Rhynchodiniopsis Deflandre, 1935, emend. Below, 1981a, Sarjeant, 1982b, Jan du Chêne et al., 1985b. This genus was emended by Jan du Chêne et al. (1985b, p.118) as follows. Proximate to proximochorate, acavate or sometimes slightly cornucavate, subspherical to polyhedral dinoflagellate cyst with an apical horn. The wall is formed of autophragm, or of periphragm and endophragm. The parasutural septa are distinct, often raised, sometimes perforate, with spinose crests. The spines can be sometimes relatively long, simple or distally bifurcate. The intratabular areas are smooth to finely ornamented. The paratabulation is clearly indicated by the parasutural septa: 2pr, 4`, 0-2pr, 6", 6c, 6``` , 1p, 1```` , xs. On the ventral surface, paraplate 6" is typically pentagonal and in contact with both 1` and 4`, this last does not touch the sulcal area. The antapical paraplate 1```` is slightly asymmetrical. At the apex, the paraplates 2` and 4` are separated by the preapicals. The archeopyle is precingular, of type P (3"), with a free operculum.
[Rhynchodiniopsis, Deflandre, 1935, p. 231; Emendations: Below, 1981a, p. 117; Sarjeant, 1982b, p. 34–35; Jan du Chêne et al., 1985b, p. 116, 118, 120.
Tax. jr. syn.: Gonyaulacysta, by implication in Millioud (1969, p.428), who illegitimately transferred the "type species" of Rhynchodiniopsis, Rhynchodiniopsis aptiana, to the junior name Gonyaulacysta — however, Lentin and Williams (1973, p.58,121) retained Gonyaulacysta.
Type species: Rhynchodiniopsis aptiana, Deflandre, 1935 (pl.5, fig.10; pl.8, figs.7–9)] ; emend. Sarjeant, 1982
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Deflandre, 1935]: (Translation: Stover and Evitt, 1978, p. 184):
Diagnosis:
Rhynchodiniopsis aptiana n.g. n.sp. strongly resembles Palaeoperidinium at first glance. Its reticulate membrane is equally similar to that of recent Peridinium. Its tabulation, which is already partially known to me, its appendices arising from a plate, its furrow ornamented from place to place with curved spines, oppose its complete assimilation into an already described genus. Certain of its characters seem to me compare with those of Hystrichosphaera (cf. infra).
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Supplemental description:
Deflandre 1936, p. 180:
Diagnosis: The most important features of Rhynchodiniopsis are: 1. a stout hollow horn at its apex, which is truncate like a snout and appears to rise from an apical plate; 2. long curved spines found at the base of the plate sutures, completely ringing the cingulum; and 3. very strong development of aliform denticulae crests, which follow all the plate sutures and border the cingulum.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Evitt, 1978, p. 184:
Synopsis:
Cysts subspherical to subpolyhedral, with an apical horn; autophragm scabrate to finely reticulate; paratabulation gonyaulacacean, indicated by parasutural ridges surmounted by fine, closely spaced spinules with prominent spines at major gonal positions; archaeopyle precingular, type P.
Description:
Shape: Subspherical to subpolyhedral, with an apical horn and rounded to truncate antapical margin.
Wall relationships: Autohragm only.
Wall features: Parasutural ridges low; crests surmounted by short, numerous, slender, closely spaced spinules or spines, and supplemented by longer gonal spines, especially along the paracingulum.
Paratabulation: indicated by parasutural ridges; gonyalacacean, formula: 3-4`, 1a, 6``, 6c?, 6```, 1p, 1````. A rectangular anterior intercalary paraplate lies between 3` and the anterior right side of 3``.
Archaeopyle: Precingular, Type P (3`` only); operculum free.
Paracingulum: Indicated by six (?) subrectangular paraplates.
Parasulcus: Delimited by parasutural features and apparently undivided.
Size: Intermediate.
Affinities:
Rhynchodiniopsis differs from Gonyaulacysta in having an autophragm (either a single wall layer or two appressed and virtually indistinguishable layers); it herefore lacks cavation, which is present in Gonyaulacysta. On Rhynchodiniopsis the spinules in the gonal positions, especially along the paracingulum, are noticeably longer than those in nongonal positions, whereas on Gonyaulacysta the denticles or spinules tend to be reduced or absent at and occasionally adjacent to the junctions of parasutural features.
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Emended descriptions:
Below, 1981: (Translations: Jan du Chêne et al., 1985: LPP)
Diagnosis:
Proximate cyst of spheroidal, ovoidal or polygonal outline, and with outstanding apical horn. Single-layered or bi-layered, but acavate. Paratabulation gonyaulacoidal: 102PR, 4`, 1-2a, 6``, Xc, 6```, 1pc, 1````, Xc (should be Xs). Of these, the preapical paraplates 1PR ans 2PR, as well as the dorsal intercalary, which is situated between 3`, 3`` and 4``, are of special importance. Parasutures indicated by ridges, surmounted by spines, thorns or distally branched appendices. Gonal spines can dominate in length compared to the parasutural spines. Paracingulum weakly spiral, parasulcus subdivided in as, ra, rs, ls, 1ps, but also often as broad, undifferentiated zones.
Archaeopyle precingular, P(3``). Operculum, compared to the size of paraplate 3``, often reduced.
-- rejected by Lentin and Williams, 1981, p. 244, without reasons given
-------------------------------------
Sarjeant, 1982:
Diagnosis:
Proximate to proximochorate dinoflagellate cyst typically of small to intermediate, rarely of large size. Ambitus ovoidal to broadly ellipsoidal or subpolygonal, consistently with an apical horn or prominence and with parasutural crests of variable form. Development of cavation at the apex consistent; acrocavate to cornucavate or, to a restricted degree, epicavate, the supplementary cavation (Where developed) being in the form of a broad base to, or small plinth for, the horn but never more extensive. Antapical and lateral cavations lacking.
Paratabulation 0-2pa, 3-4`, 1-2a, 6``, 6c, 6```, 1p, 0-1pv, 1````; the sulcus may also show subdivision into paraplates. Paraplate 4` is quite large and roughly quadrate, having a moderately long boundary with a reduced 6``. The boundary between 4` and 6`` intersects with the right lateral boundary of 1` in a position anterior to, or almost at the level of, the junction of the latter paraplate with the sulcus. Cingulum strongly or weakly helicoid; between its two ends, the sulcus is typically straight. Crests on parasutures smooth, serrate or variably developed into denticles or spines of regular or irregular length and character: accessory crests feebly developed or (typically) lacking. Height of crests variable, but always less than 1/4 of the cyst width. Gonal spines of small to moderate height, present or absent. Surface of cyst smooth, granular, nodose, punctate or reticulate.
Archaeopyle single-plate precingular, formed by loss of paraplate 3``; operculum reduced.
-------------------------------------
Jan du Chêne et al., 1985:
Diagnosis:
Proximate to proximochorate dinoflagellate cyst, acavate or sometimes slightly cornucavate, body subspherical or polyhedrical, with an apical horn. Wall formed by autophragm, or appressed periphragm and endophragm. The parasutural septa are distinct, often high, sometimes perforate, with spinous crests. These spines can sometimes be relatively long, simple or distally split. The intratabular areas are smooth to finely ornamented.
The paratabulation is clearly indicated by parasutural septa: 2pr, 4`, 0-2a, 6``, 6c, 6```, 1p, 1````, xs. Ventrally, paraplate 6`` is typically pentagonal, in contact with 1` and 4`, the latter of which does not touch the sulcal area. Antapical paraplate 1```` is slightly asymmetrical. At the apex, paraplates 2` and 4` are separated by the preapicals.
The archaeopyle is precingular, type P(3``), with a free operculum.
Affinities:
Rhynchodiniopsis differs from Acanthaulax in the absence of ornamentation on the intratabular areas. Cribroperidinium is sometimes characterized by the presence of accessory septa and especially by certain aspects of paratabulation (Helenes, 1984, p. 116-117).
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Rhynchodiniopsis Deflandre, 1935, emend. Below, 1981a, Sarjeant, 1982b, Jan du Chêne et al., 1985b. This genus was emended by Jan du Chêne et al. (1985b, p.118) as follows. Proximate to proximochorate, acavate or sometimes slightly cornucavate, subspherical to polyhedral dinoflagellate cyst with an apical horn. The wall is formed of autophragm, or of periphragm and endophragm. The parasutural septa are distinct, often raised, sometimes perforate, with spinose crests. The spines can be sometimes relatively long, simple or distally bifurcate. The intratabular areas are smooth to finely ornamented. The paratabulation is clearly indicated by the parasutural septa: 2pr, 4`, 0-2pr, 6", 6c, 6``` , 1p, 1```` , xs. On the ventral surface, paraplate 6" is typically pentagonal and in contact with both 1` and 4`, this last does not touch the sulcal area. The antapical paraplate 1```` is slightly asymmetrical. At the apex, the paraplates 2` and 4` are separated by the preapicals. The archeopyle is precingular, of type P (3"), with a free operculum.