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Nelchinopsis
From Williams et al., 2017:
[Nelchinopsis, Wiggins, 1972, p. 299; Emendation: Harding, 1996, p.352–353, 355
tax. jr. syn. of Gonyaulacysta Deflandre, 1964, according to Duxbury, 1977. Stover and Williams, 1987, retained nelchinopsis as a separate genus.
Type species: originally as Gonyaulax kostromiensis, Vozzhennikova, 1967 (pl.26, figs.1–6) (see Nelchinopsis kostromiensis for lectotype)] ; Nelchiniopsis kostromiensis, Wiggins, 1972; emend. Harding 1996
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Original description: [Wiggins, 1972]:
Description:
Proximate fossil cysts, ambitus ovoidal in shape,with a distinct apical horn. Reflected tabulation series is 1a. cl., 5`, 6a - 7a, 1a.s., 6``, 6c - 7c, 1p.s., 5```-6```,1p, 1p.v., 1````, where 1a.cl. is here defined as the apical closing plate. The archeopyle is apically situated and probably formed by the removal or partial detachment of the entire 1a. cl., 5`, 6a - 7a, la.s. tabulation sequence. Sutures are indicated by ridges or septal membranes.
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Modified description:
Stover and Evitt, 1978, p. 215-216:
Synopsis:
Cysts proximochorate, subspherical to polygonal with prominent apical horn; paratabulation indicated in part by parasutural septa and in part by low, thin, smooth parasutural ridges, latter confined to apex; combination archeopyle involves apical and anterior intercalary paraplates.
Description:
Shape: Subspherical to polygonal, apical margin with prominent broad-based horn.
Wall relationships: Autophragm only.
Wall features: Relatively high parasutural septa present posterior to apical horn; latter has low, thin, smooth parasutural ridges with smooth to granulate areas between ridges. Areas between parasutural septa bear numerous short spines.
Paratabulation: Indicated by parasutural features, formula: 1pr, 5`, 6-7a, 6``, 6-7c, 5-6```, lp, 1````, 3s. Five postcingular paraplates normally present.
Archeopyle: Combination, probably formed by the removal or partial detachment of the apical horn composed of paraplates lpr, 5`, and 6 - 7a; anterior sulcal paraplate may be involved in the formation of the archeopyle; free opercula not known to exist.
Paracingulum: Indicated by parallel transverse parasutural septa that are apparently connected by a few short longitudinal parasutural septa.
Parasulcus: Narrow, elongate, ventral area bordered and subdivided by parasutural septa.
Size: Intermediate.
Affinities:
Nelchinopsis is the only genus that has a combination archeopyle and prominent parasutural septa. Similar genera with high parasutural ridges, such as Alisocysta or Impagidinium, have either apical or precingular archeopyles and lack the dense covering of spines between parasutural features.
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Emended description:
Harding, 1996:
Diagnosis:
The same as for the single species in this genus:
Leptodinioidean cyst consisting of an autophragm supporting a thin ectophragm on densely-packed, solid, slender processes. Nature of archaeopyle uncertain, possibly apical. Paratabulation fully developed on the ectophragm as indicated by distally denticulate septa, these denticles being pronouncedly elongated in gonal positions.
Description:
Shape: Ectophragmal ambitus essentially pentagonal, made angular by the development of parasutural projections at plate triple junctions. Epicyst bell-shaped with apical plates drawn out into a broad-based, short apical horn. The horn is hollow, distally entire and measures from 9 to 14 µm in length. The autophragmal ambitus is subspherical and no apical horn is developed on this wall layer. Cyst shows greatest width across posterior cingular suture. Slight primary dorsoventral compression. Epicyst (less apical horn) and hypocyst approximately equidimensional. Cyst is holocavate with the maximum separation of wall layers being found at the parasutures.
Phragma: Ectophragm is minutely perforate and c. 0.2 µm thick. This appears to consist of partially fused sporopollenin globules (Plate II, 3); in less well preserved specimens the perforations in the layer range from subcircular holes to more sinuous fissures up to several tenths of a µm long (Plate II, 3, 6). In parasutural areas the ectophragm is developed into distally denticulate septa. The septa are up to 3 µm in height in intergonal areas, but may attain 7 µm at gonal triple junctions (Plate I, 1, 4, 7-9; Plate II, 1, 4, 7). The parasutural septa are much reduced on the apical horn, being represented by rugulate ridges usually lacking denticles. Associated with this, the horn is often compressed or collapsed and it can therefore be more difficult to discern paratabulation in the apical region (V. Wiggins, pers. commun.).
The autophragm is laevigate, of sub-micron thickness, and bears a dense cover of cylindrical processes (up to 0.5 µm in diameter; Plate II, 3). The length of the processes varies from c. 1.5 µm in intratabular areas up to c. 7 µm in the case of processes supporting the gonal projections of the parasutural septa. Slight proximal and distal flaring of the processes is observed (Plate II, 3). The junction between individual processes and the ectophragm is not consistently marked on the external cyst surface, although in some cases a small subcircular depression is formed on the exterior of the ectophragm.
Paratabulation: Expressed in the form of denticulate parasutural septa and rugulate ridges (the latter restricted to the apical horn). L-type sexiform gonyaulacoid. Paratabulation formula: 2pr, 4`, 6", 6c, 6"`, lp, 1"", 5s. Apical pattern is of the Q/B type (Plate II, 2, 7), whereas the ventral region shows the lu/li arrangement (Plate II, 2). The Y/5 suture is clearly longer than the Y/3 suture, indicating an asymmetrical quadrate arrangement of the antapical region. This is an Ornatum-type paratabulation (Helenes, 1986).
Archaeopyle: A clear excystment structure has not been recognised on any of the specimens examined. The available evidence (see below) indicates that the most likely archaeopyle type is (tA)a.
Paracingulum: Well defined, bounded by denticulate parasutural septa of equal height. Laevorotatory, displaced by 1.5-2 cingulum widths.
Parasulcus: L-type arrangement with a narrow, elongate anterior sulcal, prominent flagellar scar and a large, almost circular posterior sulcal (Z) (Plate II, 4, 5).
Remarks:
The only species of this monospecific genus was first described as Gonyaulax kostromiensis by Vozzhennikova (1967, p. 85), from borehole material from the Kostromsk region of the former USSR. These specimens are now much degraded as the glycerine jelly slides on which they were mounted have become desiccated (Lentin and Vozzhennikova, 1990). The species subsequently became known as Gonyaulacysta kostromiensis after being transferred from the living genus Gonyaulax by Sarjeant (1969, p. 10).
In 1972, Wiggins described new specimens from Alaska which he believed to be con-specific with the Russian material. Based on differences he observed between the tabulation and archaeopyle type of the Alaskan material compared to those displayed by the genus Gonyaulacysta, he erected a new mono-specific genus, Nelchinopsis, to contain both his Alaskan and Vozzhennikova`s Russian specimens.
In a palynological investigation of the Speeton Clay, Duxbury (1977), isolated dinocyst specimens which he believed not only to be con-specific with the Russian material, but also to show paratabulation entirely consistent with that of Gonyaulacysta. Thus, he retained the species kostromiensis in the latter genus. It seemed reasonable therefore that the Alaskan specimens described by Wiggins (1972), with their complex paratabulation and archaeopyle, must belong to a then unnamed species distinct from G. kostromiensis. This resulted in the erection of Alaskadinium wigginsii for the Alaskan specimens (Duxbury, 1977, p. 37). The present investigation indicates that the unusual paratabulation and archaeopyle described for the Alaskan specimens by Wiggins (1972) were artifacts of preservation, being caused by compression folds on the flattened specimens.
Stover and Williams (1987, p. 11) observed additional specimens and transparencies of the Alaskan material and believed that the Alaskan, Russian and English specimens were con-specific, indicating that Alaskadinium wigginsii was a junior synonym of Nelchinopsis kostromiensis. The recent re-examination of the Russian material of Vozzhennikova revealed that the type specimen of this species has unfortunately been lost (Lentin and Vozzhennikova, 1990, p. 109). However, five remaining specimens were located and a lectotype designated. Whilst certain details of the morphology of these specimens remain uncertain due to their poor preservational state, enough information can be gleaned to indicate that the specimens are not assignable to the genus Gonyaulacysta (Lentin and Vozzhennikova, 1990, p. 110).
The present reevaluation of Nelchinopsis kostromiensis is based partly on observation of video tape material made of light microscopic observations of the Vozzhennikova specimens and also new photographic material of the Russian specimens (both prepared and kindly provided by Dr. Judi Lentin), in addition to topotype specimens and photographic documentation of the Alaskan specimens. Importantly, new material has also been studied: most notably specimens showing perfect preservation in three dimensions from a single sample at a depth of 195 ft in the BGS Hunstanton borehole, Norfolk, England. Further specimens from Speeton, England, Gott and Frielingen, northern Germany (for details on these latter localities, see Harding, 1990), Andoya, Norway and Greenland have also been examined.
[Nelchinopsis, Wiggins, 1972, p. 299; Emendation: Harding, 1996, p.352–353, 355
tax. jr. syn. of Gonyaulacysta Deflandre, 1964, according to Duxbury, 1977. Stover and Williams, 1987, retained nelchinopsis as a separate genus.
Type species: originally as Gonyaulax kostromiensis, Vozzhennikova, 1967 (pl.26, figs.1–6) (see Nelchinopsis kostromiensis for lectotype)] ; Nelchiniopsis kostromiensis, Wiggins, 1972; emend. Harding 1996
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Original description: [Wiggins, 1972]:
Description:
Proximate fossil cysts, ambitus ovoidal in shape,with a distinct apical horn. Reflected tabulation series is 1a. cl., 5`, 6a - 7a, 1a.s., 6``, 6c - 7c, 1p.s., 5```-6```,1p, 1p.v., 1````, where 1a.cl. is here defined as the apical closing plate. The archeopyle is apically situated and probably formed by the removal or partial detachment of the entire 1a. cl., 5`, 6a - 7a, la.s. tabulation sequence. Sutures are indicated by ridges or septal membranes.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Evitt, 1978, p. 215-216:
Synopsis:
Cysts proximochorate, subspherical to polygonal with prominent apical horn; paratabulation indicated in part by parasutural septa and in part by low, thin, smooth parasutural ridges, latter confined to apex; combination archeopyle involves apical and anterior intercalary paraplates.
Description:
Shape: Subspherical to polygonal, apical margin with prominent broad-based horn.
Wall relationships: Autophragm only.
Wall features: Relatively high parasutural septa present posterior to apical horn; latter has low, thin, smooth parasutural ridges with smooth to granulate areas between ridges. Areas between parasutural septa bear numerous short spines.
Paratabulation: Indicated by parasutural features, formula: 1pr, 5`, 6-7a, 6``, 6-7c, 5-6```, lp, 1````, 3s. Five postcingular paraplates normally present.
Archeopyle: Combination, probably formed by the removal or partial detachment of the apical horn composed of paraplates lpr, 5`, and 6 - 7a; anterior sulcal paraplate may be involved in the formation of the archeopyle; free opercula not known to exist.
Paracingulum: Indicated by parallel transverse parasutural septa that are apparently connected by a few short longitudinal parasutural septa.
Parasulcus: Narrow, elongate, ventral area bordered and subdivided by parasutural septa.
Size: Intermediate.
Affinities:
Nelchinopsis is the only genus that has a combination archeopyle and prominent parasutural septa. Similar genera with high parasutural ridges, such as Alisocysta or Impagidinium, have either apical or precingular archeopyles and lack the dense covering of spines between parasutural features.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Harding, 1996:
Diagnosis:
The same as for the single species in this genus:
Leptodinioidean cyst consisting of an autophragm supporting a thin ectophragm on densely-packed, solid, slender processes. Nature of archaeopyle uncertain, possibly apical. Paratabulation fully developed on the ectophragm as indicated by distally denticulate septa, these denticles being pronouncedly elongated in gonal positions.
Description:
Shape: Ectophragmal ambitus essentially pentagonal, made angular by the development of parasutural projections at plate triple junctions. Epicyst bell-shaped with apical plates drawn out into a broad-based, short apical horn. The horn is hollow, distally entire and measures from 9 to 14 µm in length. The autophragmal ambitus is subspherical and no apical horn is developed on this wall layer. Cyst shows greatest width across posterior cingular suture. Slight primary dorsoventral compression. Epicyst (less apical horn) and hypocyst approximately equidimensional. Cyst is holocavate with the maximum separation of wall layers being found at the parasutures.
Phragma: Ectophragm is minutely perforate and c. 0.2 µm thick. This appears to consist of partially fused sporopollenin globules (Plate II, 3); in less well preserved specimens the perforations in the layer range from subcircular holes to more sinuous fissures up to several tenths of a µm long (Plate II, 3, 6). In parasutural areas the ectophragm is developed into distally denticulate septa. The septa are up to 3 µm in height in intergonal areas, but may attain 7 µm at gonal triple junctions (Plate I, 1, 4, 7-9; Plate II, 1, 4, 7). The parasutural septa are much reduced on the apical horn, being represented by rugulate ridges usually lacking denticles. Associated with this, the horn is often compressed or collapsed and it can therefore be more difficult to discern paratabulation in the apical region (V. Wiggins, pers. commun.).
The autophragm is laevigate, of sub-micron thickness, and bears a dense cover of cylindrical processes (up to 0.5 µm in diameter; Plate II, 3). The length of the processes varies from c. 1.5 µm in intratabular areas up to c. 7 µm in the case of processes supporting the gonal projections of the parasutural septa. Slight proximal and distal flaring of the processes is observed (Plate II, 3). The junction between individual processes and the ectophragm is not consistently marked on the external cyst surface, although in some cases a small subcircular depression is formed on the exterior of the ectophragm.
Paratabulation: Expressed in the form of denticulate parasutural septa and rugulate ridges (the latter restricted to the apical horn). L-type sexiform gonyaulacoid. Paratabulation formula: 2pr, 4`, 6", 6c, 6"`, lp, 1"", 5s. Apical pattern is of the Q/B type (Plate II, 2, 7), whereas the ventral region shows the lu/li arrangement (Plate II, 2). The Y/5 suture is clearly longer than the Y/3 suture, indicating an asymmetrical quadrate arrangement of the antapical region. This is an Ornatum-type paratabulation (Helenes, 1986).
Archaeopyle: A clear excystment structure has not been recognised on any of the specimens examined. The available evidence (see below) indicates that the most likely archaeopyle type is (tA)a.
Paracingulum: Well defined, bounded by denticulate parasutural septa of equal height. Laevorotatory, displaced by 1.5-2 cingulum widths.
Parasulcus: L-type arrangement with a narrow, elongate anterior sulcal, prominent flagellar scar and a large, almost circular posterior sulcal (Z) (Plate II, 4, 5).
Remarks:
The only species of this monospecific genus was first described as Gonyaulax kostromiensis by Vozzhennikova (1967, p. 85), from borehole material from the Kostromsk region of the former USSR. These specimens are now much degraded as the glycerine jelly slides on which they were mounted have become desiccated (Lentin and Vozzhennikova, 1990). The species subsequently became known as Gonyaulacysta kostromiensis after being transferred from the living genus Gonyaulax by Sarjeant (1969, p. 10).
In 1972, Wiggins described new specimens from Alaska which he believed to be con-specific with the Russian material. Based on differences he observed between the tabulation and archaeopyle type of the Alaskan material compared to those displayed by the genus Gonyaulacysta, he erected a new mono-specific genus, Nelchinopsis, to contain both his Alaskan and Vozzhennikova`s Russian specimens.
In a palynological investigation of the Speeton Clay, Duxbury (1977), isolated dinocyst specimens which he believed not only to be con-specific with the Russian material, but also to show paratabulation entirely consistent with that of Gonyaulacysta. Thus, he retained the species kostromiensis in the latter genus. It seemed reasonable therefore that the Alaskan specimens described by Wiggins (1972), with their complex paratabulation and archaeopyle, must belong to a then unnamed species distinct from G. kostromiensis. This resulted in the erection of Alaskadinium wigginsii for the Alaskan specimens (Duxbury, 1977, p. 37). The present investigation indicates that the unusual paratabulation and archaeopyle described for the Alaskan specimens by Wiggins (1972) were artifacts of preservation, being caused by compression folds on the flattened specimens.
Stover and Williams (1987, p. 11) observed additional specimens and transparencies of the Alaskan material and believed that the Alaskan, Russian and English specimens were con-specific, indicating that Alaskadinium wigginsii was a junior synonym of Nelchinopsis kostromiensis. The recent re-examination of the Russian material of Vozzhennikova revealed that the type specimen of this species has unfortunately been lost (Lentin and Vozzhennikova, 1990, p. 109). However, five remaining specimens were located and a lectotype designated. Whilst certain details of the morphology of these specimens remain uncertain due to their poor preservational state, enough information can be gleaned to indicate that the specimens are not assignable to the genus Gonyaulacysta (Lentin and Vozzhennikova, 1990, p. 110).
The present reevaluation of Nelchinopsis kostromiensis is based partly on observation of video tape material made of light microscopic observations of the Vozzhennikova specimens and also new photographic material of the Russian specimens (both prepared and kindly provided by Dr. Judi Lentin), in addition to topotype specimens and photographic documentation of the Alaskan specimens. Importantly, new material has also been studied: most notably specimens showing perfect preservation in three dimensions from a single sample at a depth of 195 ft in the BGS Hunstanton borehole, Norfolk, England. Further specimens from Speeton, England, Gott and Frielingen, northern Germany (for details on these latter localities, see Harding, 1990), Andoya, Norway and Greenland have also been examined.