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Gonyaulacysta eisenackii
Gonyaulacysta eisenackii (Deflandre, 1938) Gorka, 1965; emend. Sarjeant, 1982
Originally Gonyaulax, subsequently (and now) Gonyaulacysta, thirdly Endoscrinium, fourthly Tubotuberella.
Sarjeant, 1982, considered the subspecies Gonyaulacysta eisenackii ssp. oligodentata (Cookson and Eisenack, 1958) Sarjeant, 1972, to be synonymous with Gonyaulacysta eisenackii ssp. eisenackii.
Tax. sr. synonym of Tubotuberella sphaerocephalis Vozzhennikova, 1967, according to Sarjeant, 1983).
Dodekova, 1967, and Sarjeant, 1968, also effected the transfer of this species to Gonyaulacysta.
Jan du Chene et al., 1986, and Brenner, 1988, retained this species in Tubotuberella Vozzhennikova, 1967.
Lentin and Williams, 1989, retained the species in Gonyaulacysta.
This combination was not validly published in Sarjeant, 1966, since that author did not fully reference the basionym.
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Gonyaulacysta eisenackii (Deflandre, 1939a) Górka, 1965, emend. Sarjeant, 1982b. According to Sarjeant (1982b), Gonyaulacysta eisenackii is prolonged apically into a short horn or mamelon. There is consistently an epipericoel; the hypopericoel, where developed is small. Parasutures marked by low to moderately high crests of variable form, irregularly denticulate, echinate, or acanthate, etc. Has a tabulation of 2pr, 4', 0-?2a, 6", 6c, 6"’, 1p, 1ps, 1"”. There can be an opisthopyle. This species differs from G.jurassica in the relative proportion of the epitract and hypotract, the lesser degree of development of the epipericoel and or apical horn, and the detail of the anterior tabulation. And the crests tend to give rise to stronger and more widely spaced prominences or spines, the crests surrounding the antapex being especially high and most coarsely spinose.
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Holotype: Deflandre, 1938, pl.6, figs.7-8, text-figs.3-4; Jan du Chene et al., 1986, pl.125, figs.5-9
Locus typicus: Villers-sur-mer, Calvados, France
Stratum typicum: Oxfordian
Translation Deflandre, 1938: LPP
Original description: Deflandre 1938, p. 171-173: Gonyaulax eisenackii
In frontal view, this species looks rhomboidal, with a truncate lower pole. The transverse furrow is strongly helicoidal and the tw halves are clearly of equal size. The epiteca is conical and ends in a slightly truncate or bifid tip. The hypotheca is truncate and asymmetrical in lateral view resulting from the strong development of a sutural septum stemming from a postequatorial dorsal plate which forms a comb with five or six teeth. The sutures bear well-developed spinous or serrate septa, that show spines included in the membrane of the septum. At the junctions of the septa, more or less well-developed thorns are present. On the epitheca, these thorns are generally stronger on the upper corners between the first and second pre-equatorial plate and between the fourth and fifth pre-equatorial. On the hypotheca, this is always the case on the two distal corners of the fourth postequatorial. There are six pre-equatorial plates. the sixth is notably smaller and appears to be of variable shape (curved to trapezoidal (plate 6, figs.8 and 10). There seem to be 4 apical plates, but the two straight plates may be part of the longitudinal furrow. It is necessary to study the apical view. The hypotheca has six post-equatorial plates, the first of which is very small. Sometimes it is difficult to discern the tiny plates on the ventral side. The very small postequatorial plate is often found in Recent Gonyaulax. There is just one antapical plate and one posterior intercalary, bordering the first two post-equatorials. The tabulation of the hypotheca is very characteristic and resembles that of Recent Gonyaulax. The thecal membrane appears to be smooth, maybe very lightly punctate. Where verifiable, the third (dorsal) pre-equatorial plate was missing, like in G. jurassica. All specimens show straight sides, in only one specimen they are slightly concave. Some specimens appear to be shorter than the depicted ones.
Approximate dimensions: length 65-80 Ám, breadth 57-60 Ám.
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Emended diagnosis: Sarjeant 1982, p. 33
Cyst elongate polygonal (asymmetrically pentagonal to rounded-pentagonal) in ambitus, prolonged apically into a mamelon or short horn. Epitract and hypotract of almost equal size; epitract hemispherical to almost triangular in ambitus, hypotract having the form of an inverted cone truncated at about two-thirds its height. Epipericoel consistently developed, sometimes confined to the horn, more often broader, either forming a broad-based triangle culminating in the apical prominence or forming a sort of plinth from which that prominence arises, but not forming a significant anterior extension of the epitract. (The epipericoel never occupies more than one-third of the total length of the epitract). Hypopericoel (where developed) small, much broader than long and often masked by the high crests surrounding the antapex. Parasutures well marked by low to moderately high crests of variable form--irregularly to regularly denticulate, echinate or acanthate, loricate or phractate, or exhibiting complex intermediates between these types. Gonal spinules present or absent; where present, typically not, or only slightly, higher than the surrounding crests. Paratabulation 2pa, 4', 0-?2a, 6", 6c, 6"', 1p, 1pv, 1"", 0-xs. Paraplate 4' is small and elongate, less long than 1' and with only minor contact with paraplate 6"; the latter ranges from triangular, with one convex and one concave face, to almost crescentic in shape. The crest separating 4' and 6" intersects the right lateral crest of 1' at a position markedly anterior to the junction of the latter paraplate with the sulcus. In delphicavate or bicavate forms, the antapical paraplate may be penetrated, or entirely occupied, by an opisthopyle. Archaeopyle single-plate precingular, formed by loss of paraplate 3"; operculum reduced.
Discussion: Gonyaulacysta eisenackii resembles G. jurassica in general form, but differs in the relative proportions of epitract and hypotract, the lesser degree of development of the epipericoel and/or apical horn, and the detail of its anterior ventral paratabulation. In addition, though the crests of both species are variable, those of G. eisenackii tend to give rise to stronger and more widely spaced prominences or spines, the crests surrounding the antapex being especially high and most coarsely spinose. Gonyaulacysta pectinigera (GOCHT, 1970) emend. Fensome 1979 is more symmetrically pentagonal (i.e. broader) in ambitus, without a hypopericoel or opisthopyle; its crests are variable but tend to have more closely spaced denticles or spines (see Pl. 7, fig. 7).
MORPHOLOGY OF Gonyaulacysta eisenackii: Sarjeant 1982, p. 19-25
Dinoflagellate cysts having a lozenge-shaped to elongate pentagonal outline, typically bicavate, with crests varying in height and form, are a component of Late Mesozoic assemblages from Middle Jurassic (Bathonian or earlier) to Late Cretaceous. Several species have been distinguished; since the earliest, in order of publication, was Deflandre's G. eisenackii, it is this species that will be considered first. All the type material was examined, though only the holotype is illustrated (pl. 7, figs. 5, 6). In addition, specimens from a number of English horizons were considered, one being here illustrated (pl. 8, fig. 3). None of the assemblages, unfortunately, were sufficiently rich in specimens of C. eisenackii for a proper study of its variation to be undertaken. The comments below must be regarded as provisional, pending such a study.
The cyst is roughly hexagonal in ambitus, with epitract and hypotract almost equal in size and both having the forms of truncated cones (the apical prominence is here omitted from consideration, as in C. jurassica). In lateral view, the cyst assumes an almost lozenge-shaped profile, though the antapical flattening remains apparent (see pl. 8, fig. 3). The epipericoel is broad and shallow, more or less abruptly giving rise at its centre to a very short apical protrusion or horn. Two preapicals are developed at the tip of this horn: and it is probable that, as in G. jurassica, two small dorsal intercalaries are developed, though no specimen seen afforded unequivocal evidence of their presence.
The anterior ventral paratabulation is of particular interest. Since Deflandre's drawing of the holotype (1938, pl. 6, fig. 8) is quite accurate, a modified version of it is presented here (Text-fig. 4). The fourth apical paraplate, as in G. jurassica, is narrow and elongate but shorter than the first. The contact of the fourth apical paraplate with the sixth precingular is small and the latter paraplate is subtriangular to almost crescentic in shape. Again, as in G. jurassica, the boundary separating 4' and 6" intersects that bounding 1' in a position markedly anterior to the junction of the latter paraplate with the sulcus. A reduced paraplate 1"' and a larger 2"' are both separated from the antapex by paraplate 1p; the other four postcingulars are of relatively uniform size. A posterior ventral paraplate is developed; it is not penetrated by any opisthopyle.
The hypopericoel is comparable in size and form (ignoring the apical horn) to the epipericoel and does not modify the ambitus of the hypotract. Crests are high generally and of varied form; denticulate, echinate and hystricate styles were all observed and a greater range of variation may be expected in a more extensive material. The crests are at their highest about the antapex and tend to mask from view the large opisthopyle penetrating (or, rather, replacing) that paraplate in the periblast. Though clearly separate at the specific level, the species G. eisenackii is in all features too close to G. jurassica to be separated from it at the generic level. Accordingly, in the taxonomic section that follows, it is returned to Gonyaulacysta.
Originally Gonyaulax, subsequently (and now) Gonyaulacysta, thirdly Endoscrinium, fourthly Tubotuberella.
Sarjeant, 1982, considered the subspecies Gonyaulacysta eisenackii ssp. oligodentata (Cookson and Eisenack, 1958) Sarjeant, 1972, to be synonymous with Gonyaulacysta eisenackii ssp. eisenackii.
Tax. sr. synonym of Tubotuberella sphaerocephalis Vozzhennikova, 1967, according to Sarjeant, 1983).
Dodekova, 1967, and Sarjeant, 1968, also effected the transfer of this species to Gonyaulacysta.
Jan du Chene et al., 1986, and Brenner, 1988, retained this species in Tubotuberella Vozzhennikova, 1967.
Lentin and Williams, 1989, retained the species in Gonyaulacysta.
This combination was not validly published in Sarjeant, 1966, since that author did not fully reference the basionym.
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Gonyaulacysta eisenackii (Deflandre, 1939a) Górka, 1965, emend. Sarjeant, 1982b. According to Sarjeant (1982b), Gonyaulacysta eisenackii is prolonged apically into a short horn or mamelon. There is consistently an epipericoel; the hypopericoel, where developed is small. Parasutures marked by low to moderately high crests of variable form, irregularly denticulate, echinate, or acanthate, etc. Has a tabulation of 2pr, 4', 0-?2a, 6", 6c, 6"’, 1p, 1ps, 1"”. There can be an opisthopyle. This species differs from G.jurassica in the relative proportion of the epitract and hypotract, the lesser degree of development of the epipericoel and or apical horn, and the detail of the anterior tabulation. And the crests tend to give rise to stronger and more widely spaced prominences or spines, the crests surrounding the antapex being especially high and most coarsely spinose.
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Holotype: Deflandre, 1938, pl.6, figs.7-8, text-figs.3-4; Jan du Chene et al., 1986, pl.125, figs.5-9
Locus typicus: Villers-sur-mer, Calvados, France
Stratum typicum: Oxfordian
Translation Deflandre, 1938: LPP
Original description: Deflandre 1938, p. 171-173: Gonyaulax eisenackii
In frontal view, this species looks rhomboidal, with a truncate lower pole. The transverse furrow is strongly helicoidal and the tw halves are clearly of equal size. The epiteca is conical and ends in a slightly truncate or bifid tip. The hypotheca is truncate and asymmetrical in lateral view resulting from the strong development of a sutural septum stemming from a postequatorial dorsal plate which forms a comb with five or six teeth. The sutures bear well-developed spinous or serrate septa, that show spines included in the membrane of the septum. At the junctions of the septa, more or less well-developed thorns are present. On the epitheca, these thorns are generally stronger on the upper corners between the first and second pre-equatorial plate and between the fourth and fifth pre-equatorial. On the hypotheca, this is always the case on the two distal corners of the fourth postequatorial. There are six pre-equatorial plates. the sixth is notably smaller and appears to be of variable shape (curved to trapezoidal (plate 6, figs.8 and 10). There seem to be 4 apical plates, but the two straight plates may be part of the longitudinal furrow. It is necessary to study the apical view. The hypotheca has six post-equatorial plates, the first of which is very small. Sometimes it is difficult to discern the tiny plates on the ventral side. The very small postequatorial plate is often found in Recent Gonyaulax. There is just one antapical plate and one posterior intercalary, bordering the first two post-equatorials. The tabulation of the hypotheca is very characteristic and resembles that of Recent Gonyaulax. The thecal membrane appears to be smooth, maybe very lightly punctate. Where verifiable, the third (dorsal) pre-equatorial plate was missing, like in G. jurassica. All specimens show straight sides, in only one specimen they are slightly concave. Some specimens appear to be shorter than the depicted ones.
Approximate dimensions: length 65-80 Ám, breadth 57-60 Ám.
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Emended diagnosis: Sarjeant 1982, p. 33
Cyst elongate polygonal (asymmetrically pentagonal to rounded-pentagonal) in ambitus, prolonged apically into a mamelon or short horn. Epitract and hypotract of almost equal size; epitract hemispherical to almost triangular in ambitus, hypotract having the form of an inverted cone truncated at about two-thirds its height. Epipericoel consistently developed, sometimes confined to the horn, more often broader, either forming a broad-based triangle culminating in the apical prominence or forming a sort of plinth from which that prominence arises, but not forming a significant anterior extension of the epitract. (The epipericoel never occupies more than one-third of the total length of the epitract). Hypopericoel (where developed) small, much broader than long and often masked by the high crests surrounding the antapex. Parasutures well marked by low to moderately high crests of variable form--irregularly to regularly denticulate, echinate or acanthate, loricate or phractate, or exhibiting complex intermediates between these types. Gonal spinules present or absent; where present, typically not, or only slightly, higher than the surrounding crests. Paratabulation 2pa, 4', 0-?2a, 6", 6c, 6"', 1p, 1pv, 1"", 0-xs. Paraplate 4' is small and elongate, less long than 1' and with only minor contact with paraplate 6"; the latter ranges from triangular, with one convex and one concave face, to almost crescentic in shape. The crest separating 4' and 6" intersects the right lateral crest of 1' at a position markedly anterior to the junction of the latter paraplate with the sulcus. In delphicavate or bicavate forms, the antapical paraplate may be penetrated, or entirely occupied, by an opisthopyle. Archaeopyle single-plate precingular, formed by loss of paraplate 3"; operculum reduced.
Discussion: Gonyaulacysta eisenackii resembles G. jurassica in general form, but differs in the relative proportions of epitract and hypotract, the lesser degree of development of the epipericoel and/or apical horn, and the detail of its anterior ventral paratabulation. In addition, though the crests of both species are variable, those of G. eisenackii tend to give rise to stronger and more widely spaced prominences or spines, the crests surrounding the antapex being especially high and most coarsely spinose. Gonyaulacysta pectinigera (GOCHT, 1970) emend. Fensome 1979 is more symmetrically pentagonal (i.e. broader) in ambitus, without a hypopericoel or opisthopyle; its crests are variable but tend to have more closely spaced denticles or spines (see Pl. 7, fig. 7).
MORPHOLOGY OF Gonyaulacysta eisenackii: Sarjeant 1982, p. 19-25
Dinoflagellate cysts having a lozenge-shaped to elongate pentagonal outline, typically bicavate, with crests varying in height and form, are a component of Late Mesozoic assemblages from Middle Jurassic (Bathonian or earlier) to Late Cretaceous. Several species have been distinguished; since the earliest, in order of publication, was Deflandre's G. eisenackii, it is this species that will be considered first. All the type material was examined, though only the holotype is illustrated (pl. 7, figs. 5, 6). In addition, specimens from a number of English horizons were considered, one being here illustrated (pl. 8, fig. 3). None of the assemblages, unfortunately, were sufficiently rich in specimens of C. eisenackii for a proper study of its variation to be undertaken. The comments below must be regarded as provisional, pending such a study.
The cyst is roughly hexagonal in ambitus, with epitract and hypotract almost equal in size and both having the forms of truncated cones (the apical prominence is here omitted from consideration, as in C. jurassica). In lateral view, the cyst assumes an almost lozenge-shaped profile, though the antapical flattening remains apparent (see pl. 8, fig. 3). The epipericoel is broad and shallow, more or less abruptly giving rise at its centre to a very short apical protrusion or horn. Two preapicals are developed at the tip of this horn: and it is probable that, as in G. jurassica, two small dorsal intercalaries are developed, though no specimen seen afforded unequivocal evidence of their presence.
The anterior ventral paratabulation is of particular interest. Since Deflandre's drawing of the holotype (1938, pl. 6, fig. 8) is quite accurate, a modified version of it is presented here (Text-fig. 4). The fourth apical paraplate, as in G. jurassica, is narrow and elongate but shorter than the first. The contact of the fourth apical paraplate with the sixth precingular is small and the latter paraplate is subtriangular to almost crescentic in shape. Again, as in G. jurassica, the boundary separating 4' and 6" intersects that bounding 1' in a position markedly anterior to the junction of the latter paraplate with the sulcus. A reduced paraplate 1"' and a larger 2"' are both separated from the antapex by paraplate 1p; the other four postcingulars are of relatively uniform size. A posterior ventral paraplate is developed; it is not penetrated by any opisthopyle.
The hypopericoel is comparable in size and form (ignoring the apical horn) to the epipericoel and does not modify the ambitus of the hypotract. Crests are high generally and of varied form; denticulate, echinate and hystricate styles were all observed and a greater range of variation may be expected in a more extensive material. The crests are at their highest about the antapex and tend to mask from view the large opisthopyle penetrating (or, rather, replacing) that paraplate in the periblast. Though clearly separate at the specific level, the species G. eisenackii is in all features too close to G. jurassica to be separated from it at the generic level. Accordingly, in the taxonomic section that follows, it is returned to Gonyaulacysta.