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Gonyaulacysta jurassica
From Fensome et al., 2019:
Gonyaulacysta jurassica (Deflandre, 1939a, p.168, pl.6, figs.2–5; text-figs.1–2) Norris and Sarjeant, 1965, p.65. Emendation: Sarjeant, 1982b, p.28–30, as Gonyaulacysta jurassica. Holotype: Deflandre, 1939a, pl.6, figs.2–3; text-figs.1–2; Jan du Chêne et al., 1986a, pl.37, figs.1–3. Originally Gonyaulax (Appendix B), subsequently (and now) Gonyaulacysta. Taxonomic junior synonym: Psaligonyaulax (as and now Gonyaulacysta) dualis, according to Sarjeant (1982b, p.29) — however, Jan du Chêne et al. (1986a, p.131) retained Gonyaulacysta dualis. Górka (1965, p.298) also proposed this combination. Age: Oxfordian.
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Paratypes: Deflandre, 1938; Sarjeant, 1982; Jan du Chene et al., 1986, pl.37, fig.4-6
Locus typicus: Villers-sur-Mer, Calvados, France
Translation Deflandre, 1938: LPP
Original description: Deflandre 1938, p. 168: Gonyaulax jurassica
(annotated) The cell is elongate, generally polygonal in frontal view and the helocoidal transverse furrow divides it into two unequal parts. The epitheca, always larger than the hypotheca, is more or less conical and terminates in a clearly cylindrical, hollow horn. The sides of the epitheca are straight ot slightly concave or convex. The same holds for the hypotheca, the sides of which, however, are more rarely convex. The hypohteca is trapezoidal, sometimes with a slightly rounded pole.
The plate-sutures bear thin, but relatively high ribs with finely denticulate rims. The transverse furrow as well (but not always) bears fine denticulations on its rim. On the hypotheca, the plate-sutures lenghten gonally into short denticulate horns, the development of which varies per specimen.
The epitheca has six preequatorial plates, the sixth of which is clearly more reduced than the others. Three apical plates join to form the tubular apical horn; one, adjacent to the sixth preequatorial plate, is situated in line with the longitudinal furrow, the others are adjacent to the preequatorials 1-2-3 and 3-4-5 respectively, their sutural line clearly running into the area of the upper part of of the third preequatorial. In all specimens, the third preequatorial is missing.
The hypotheca has six postequatorial plates, one polygonal antapical plate and an inermediate. The first postequatorial plate (1''') is very reduced and remains easily unnoticed. The intermediate plate (1p) is adjacent to the second and third preequatorial (sic, should be: postequatorial), to the antapical plate and the longitudinal furrow. The sutural ribs between plates 2-3, 3-4, 4-5 and 5-6 lengthen, as described earlier, into four denticulate horns, sometimes very reduced, sometimes very well developed. Some specimens of G. jurassica, until now rarely, have a fifth horn, situated on the suture 2-3, at the corner of plates 2''' and 1p.
The general form of G. jurassica mainly varies from bulging specimens with convex sides to specimens with concave sides.
The membrane on most specimens appears to be smooth or at the most finely punctate.
Dimensions: holotype 79x55 µm. Range: length 60-100 µm.
Supplemental description: Pocock, 1972, p.88
Vesicle longer than it is broad; epitheca hemispherical; terminated by a prominent, blunt-tipped horn made up of three elongate thecal plates (1', 2', and 3'); equatorial furrow well developed, helicoidal; hypotheca hemispherical; longitudinal furrow widest towards the antapex, narrowing to a point on the epitheca were it abuts against the antapical end of plate 1'; tabulation 3', 6", 6''', 1''''; sutures well defined, forming relatively wide ridges, usually finely serrate at their crests; test thin-walled; smooth; colourlless to pale yellow; length of test (inclusive of apical horn and crest to plate 1'''') 103.0--105 µm (ridges shortest at equator; longest on plate 1'''').
Emended diagnosis: Sarjeant, 1982, p. 30
Cyst irregularly hexagonal to rounded-hexagonal in ambitus, prolonged apically into a mamelon or horn of highly variable length. Epitract in the form of a cone truncated at one-half to two-thirds height; hypotract smaller, in the form of an inverted cone truncated at one-third to one-half its height. Flanks of epitract and hypotract convex, planar or slightly concave. Epipericoel consistently developed, sometimes entirely confined to the horn, more often also occupying the apical region of the cyst to a varying degree; a hypopericoel may be present, developed only marginally, or completely lacking. Paraplates well marked by low to moderately high crests of variable form-irregularly to regularly serrate, denticulate, echinate or acanthate; crenellate, hystricate or phractate; or exhibiting complex intermediates between these types. Gonal spines present or absent, sometimes longest at the antapex and sustaining caudiculae. Paratabulation 2pa, 4', 2a, 6'', 6c, 6''', 1p, 1pv, 1''''. Paraplate 4' is elongate, less long than 1', with only a small contact with an elongate triangular 6''. The crests separating 4' from 6'' intersects the right lateral crest of 1' in a position markedly anterior to the junction of the latter paraplate with the sulcus. Archaeopyle single-plate precingular, formed by loss of paraplate 3'''; an opisthopyle may be developed in paraplate 1pv of delphicavate or bicavate specimens.
Affinities:
Pocock, 1972, p. 88: The Canadian specimens are larger, on average, than European ones, but there can be little doubt as to their identity. The smoothly ovoid test with prominent apical horn, wide sutural ridges and comparatively simple plating are characteristic of this species.
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Riding et al., 2022:
Emended diagnosis: A species of Gonyaulacysta that is subpentagonal in outline, bicavate, intermediate in size, has a longitudinal L-type sulcus and a moderately large apical horn that is variable in shape.Most of the sutural features are prominent denticulate crests. Both the periphragm and endophragm are smooth.
Emended description: A species of Gonyaulacysta, subpentagonal in outline, with bicavate cyst organisation and intermediate in size. Some plate boundaries may exhibit suturocavation, especially in the precingular series. The moderately well-developed apical horn is formed by the periphragm; it may be relatively slender (delphicavate) and is always truncate distally. The endocyst may be ovoidal and may exhibit a small rounded apical protuberance. The tabulation is reflected by prominent sutural ridges or crests that vary in height and are distally denticulate. The sulcus is longitudinal, L-type. Gonal spinesmay be present on crests bounding the 1′′′′ plate; where present, they are 2–7 μm height. The ellipsoidal opisthopyle on the ps plate is normally evident. The periphragm and endophragm are both smooth.
Holotype: Specimen AO 55 of Deflandre (1938, pl. 6, 2, 3; figs. 1, 2). The sample is from the lowermost Oxfordian Marnes de Villers Formation (Quenstedtoceras mariae ammonite zone, Villers sur Mer, Calvados, northern France. Curated in the Institut de Paléontologie, Musée Nationale d'Historie Naturelle, Paris, France.
Comments: Gonyaulacysta jurassica, the type of the genus, was established by Deflandre (1938). It is easy to recognise, being bicavate, having an apical horn of moderate size, and bearing denticulate crests. However, prior to the work of Sarjeant (1982), palynologists did not distinguish the epicavate specimens characteristic of the Callovian from the bicavate forms so distinctive of the Oxfordian and Kimmeridgian. Sarjeant (1982) established Gonyaulacysta jurassica subsp. adecta for the former group, the subspecies Gonyaulacysta jurassica subsp. jurassica being automatically established for the latter group because it includes the type of the species. This finding was a genuine breakthrough, because the earliest Oxfordian range base of Gonyaulacysta jurassica subsp. jurassica (now Gonyaualacysta jurassica in the restricted sense) is an extremely useful biostratigraphical marker (Fig. 3). We propose below that Gonyaulacysta jurassica subsp. adecta should have species status. Thus, Gonyaulacysta jurassica subsp. adecta is raised to species rank, therebymaking Gonyaulacysta jurassica subsp. jurassica redundant. Gonyaulacysta jurassica sensu stricto isemended here to focus on the detailed overallmorphology, for example the suturocavation, the shape of the epicyst and the hypocystal cavation. The cavation in the epicyst of Gonyaulacysta jurassica is highly variable (Sarjeant, 1982, fig. 1). When describing the holotype of Gonyaulacysta jurassica, Sarjeant (1982, p. 14) noted that the periphragm and endophragm of the hypocyst were separated laterally, but still in contact at the antapex. He included this feature in his description of Gonyaulacysta jurassica subsp. jurassica, stating that this subspecies exhibits a partial or complete development of the hypopericoel (Sarjeant, 1982, p. 30). Poulsen (1991, p. 213) restudied the holotype and demonstrated the complete separation of the two wall layers in the antapical region and therefore, Gonyaulacysta jurassica subsp. jurassica is clearly bicavate. Poulsen (1991, p. 213) stated that the opisthopyle is in the 1′′′′ plate. The present emendation revises this to the ps plate. The emendation of Gonyaulacysta jurassica subsp. jurassica (equatingwith our concept of Gonyaualacysta jurassica) by Sarjeant (1982, p. 30) lacks key details. Gonyaulacysta jurassica is significantly variable in size, an aspect fully discussed below.
Comparison: The most similar species to Gonyaulacysta jurassica is Gonyaulacysta adecta, but the latter is consistently epicavate. Gonyaulacysta desmos, like Gonyaulacysta jurassica, has pericoels but is only partially antapically cavate (Fig. 2).
Dimensions: We have observed that the size of Gonyaulacysta jurassica significantly increased throughout its range. In order to investigate this phenomenon, material from Staffin Bay, Isle of Skye in northwestern Scotland and Lincolnshire in eastern England has been examined (Fig. 4, Table 2, Supplementary material Appendix 3, table 1). Measurements were carried out on 120 specimens from each locality, collectively covering the entire Oxfordian to lower Kimmeridgian succession. From the lower to middle Oxfordian the average length varies only slightly, decreasing from 69 μm to 67μm for the Scottish material and from 67 μm to 66 μm for the English material (Fig. 4). However, in the upper Oxfordian and Kimmeridgian, specimens of Gonyaulacysta jurassica are significantly larger. The major increase is recorded at the base of the upper Oxfordian, where the average length increases by 12 μm and 11 μm in Scotland and England respectively (Fig. 4). This was followed by a slight decrease in the lower Kimmeridgian at both localities. The results from both areas are clearly consistent with one another, suggesting that the overall trend is not arbitrary or controlled, for example, sedimentologically.
The dimensions of Gonyaulacysta jurassica studied herein, based on 120 specimens from the lower and middle Oxfordian, are: length of pericyst, 53 (67) 84; length of apical horn, 7 (12) 18; length of epipericyst, 33 (42) 58; length of hypopericyst, 13 (20) 31; length of endocyst, 33 (47) 62; width at cingulum, 36 (45) 60. The dimensions of material from the upper Oxfordian and lower Kimmeridgian, again based on 120 specimens, are: length of pericyst, 60 (77) 100; length of apical horn, 9 (14) 20; length of epipericyst, 33 (45) 60; length of hypopericyst, 13 (26) 40; length of endocyst, 40 (54) 71; width at cingulum, 33 (50) 69 (Supplementary material Appendix 3, table 1). The average length and width from the upper Oxfordian and lower Kimmeridgian compare well with the original material of Deflandre (1938, p.169–170); i.e. length of pericyst, 79; width at cingulum, 55. Deflandre (1938) also stated that the largest specimens reached 100 μm in length, whereas the smallest ones were 65 μm long in his early Oxfordian material.
Geographical and stratigraphical distribution: Gonyaulacysta jurassica occurs worldwide and is a prominent Late Jurassic species. In Europe and surrounding regions in the Northern Hemisphere, including the Arctic, it is confined to the Oxfordian and Kimmeridgian (Quenstedtoceras mariae to Aulacostephanus autissiodorensis ammonite zones; Fig. 3), and its range base and top are reliable stratigraphical markers (e.g., Feist- Burkhardt and Wille, 1992; Riding and Thomas, 1992; Poulsen and Riding, 2003). Throughout the Oxfordian and Kimmeridgian in Europe, Gonyaulacysta jurassica is normally relatively common (e.g., Brenner, 1988; Kunz, 1990; Riding and Thomas, 1997; Riding et al., 1999; Riding, 2005b), especially in the Oxfordian.
The species is also present in the Southern Hemisphere. In Australasia, Gonyaulacysta jurassica has a range of middle Bathonian to middle Kimmeridgian. It is only consistently present between the latest Bathonian and middle Oxfordian (Riding et al., 2010, fig. 12). The species does not occur in the late Bajocian to early Bathonian Wanaea verrucosa dinoflagellate cyst zone (Mantle and Riding, 2012). There are reports of sporadic specimens of Gonyaulacysta jurassica fromthe late Kimmeridgian to earliest Cretaceous in Australasia (Helby et al., 1987; Davey, 1988); however, these occurrences are believed to represent reworking.
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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 jurassica (Deflandre, 1939a) Norris and Sarjeant, 1965, emend. Sarjeant, 1982b. According to Sarjeant (1982b), Gonyaulacysta jurassica has a tabulation of 2pa, 4', 2a, 6", 6c, 6"’, 1p, 1pv, 1"”. The epicyst is always considerably longer than the hypocyst and there is an epicystal pericoel below the apical horn. Sometimes there is an opisthopyle. G.jurassica is also characterised by the parasutural septa with serrated crests. The 6" plate is elongate. Size:
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Gonyaulacysta jurassica (Deflandre, 1939a, p.168, pl.6, figs.2–5; text-figs.1–2) Norris and Sarjeant, 1965, p.65. Emendation: Sarjeant, 1982b, p.28–30, as Gonyaulacysta jurassica. Holotype: Deflandre, 1939a, pl.6, figs.2–3; text-figs.1–2; Jan du Chêne et al., 1986a, pl.37, figs.1–3. Originally Gonyaulax (Appendix B), subsequently (and now) Gonyaulacysta. Taxonomic junior synonym: Psaligonyaulax (as and now Gonyaulacysta) dualis, according to Sarjeant (1982b, p.29) — however, Jan du Chêne et al. (1986a, p.131) retained Gonyaulacysta dualis. Górka (1965, p.298) also proposed this combination. Age: Oxfordian.
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Paratypes: Deflandre, 1938; Sarjeant, 1982; Jan du Chene et al., 1986, pl.37, fig.4-6
Locus typicus: Villers-sur-Mer, Calvados, France
Translation Deflandre, 1938: LPP
Original description: Deflandre 1938, p. 168: Gonyaulax jurassica
(annotated) The cell is elongate, generally polygonal in frontal view and the helocoidal transverse furrow divides it into two unequal parts. The epitheca, always larger than the hypotheca, is more or less conical and terminates in a clearly cylindrical, hollow horn. The sides of the epitheca are straight ot slightly concave or convex. The same holds for the hypotheca, the sides of which, however, are more rarely convex. The hypohteca is trapezoidal, sometimes with a slightly rounded pole.
The plate-sutures bear thin, but relatively high ribs with finely denticulate rims. The transverse furrow as well (but not always) bears fine denticulations on its rim. On the hypotheca, the plate-sutures lenghten gonally into short denticulate horns, the development of which varies per specimen.
The epitheca has six preequatorial plates, the sixth of which is clearly more reduced than the others. Three apical plates join to form the tubular apical horn; one, adjacent to the sixth preequatorial plate, is situated in line with the longitudinal furrow, the others are adjacent to the preequatorials 1-2-3 and 3-4-5 respectively, their sutural line clearly running into the area of the upper part of of the third preequatorial. In all specimens, the third preequatorial is missing.
The hypotheca has six postequatorial plates, one polygonal antapical plate and an inermediate. The first postequatorial plate (1''') is very reduced and remains easily unnoticed. The intermediate plate (1p) is adjacent to the second and third preequatorial (sic, should be: postequatorial), to the antapical plate and the longitudinal furrow. The sutural ribs between plates 2-3, 3-4, 4-5 and 5-6 lengthen, as described earlier, into four denticulate horns, sometimes very reduced, sometimes very well developed. Some specimens of G. jurassica, until now rarely, have a fifth horn, situated on the suture 2-3, at the corner of plates 2''' and 1p.
The general form of G. jurassica mainly varies from bulging specimens with convex sides to specimens with concave sides.
The membrane on most specimens appears to be smooth or at the most finely punctate.
Dimensions: holotype 79x55 µm. Range: length 60-100 µm.
Supplemental description: Pocock, 1972, p.88
Vesicle longer than it is broad; epitheca hemispherical; terminated by a prominent, blunt-tipped horn made up of three elongate thecal plates (1', 2', and 3'); equatorial furrow well developed, helicoidal; hypotheca hemispherical; longitudinal furrow widest towards the antapex, narrowing to a point on the epitheca were it abuts against the antapical end of plate 1'; tabulation 3', 6", 6''', 1''''; sutures well defined, forming relatively wide ridges, usually finely serrate at their crests; test thin-walled; smooth; colourlless to pale yellow; length of test (inclusive of apical horn and crest to plate 1'''') 103.0--105 µm (ridges shortest at equator; longest on plate 1'''').
Emended diagnosis: Sarjeant, 1982, p. 30
Cyst irregularly hexagonal to rounded-hexagonal in ambitus, prolonged apically into a mamelon or horn of highly variable length. Epitract in the form of a cone truncated at one-half to two-thirds height; hypotract smaller, in the form of an inverted cone truncated at one-third to one-half its height. Flanks of epitract and hypotract convex, planar or slightly concave. Epipericoel consistently developed, sometimes entirely confined to the horn, more often also occupying the apical region of the cyst to a varying degree; a hypopericoel may be present, developed only marginally, or completely lacking. Paraplates well marked by low to moderately high crests of variable form-irregularly to regularly serrate, denticulate, echinate or acanthate; crenellate, hystricate or phractate; or exhibiting complex intermediates between these types. Gonal spines present or absent, sometimes longest at the antapex and sustaining caudiculae. Paratabulation 2pa, 4', 2a, 6'', 6c, 6''', 1p, 1pv, 1''''. Paraplate 4' is elongate, less long than 1', with only a small contact with an elongate triangular 6''. The crests separating 4' from 6'' intersects the right lateral crest of 1' in a position markedly anterior to the junction of the latter paraplate with the sulcus. Archaeopyle single-plate precingular, formed by loss of paraplate 3'''; an opisthopyle may be developed in paraplate 1pv of delphicavate or bicavate specimens.
Affinities:
Pocock, 1972, p. 88: The Canadian specimens are larger, on average, than European ones, but there can be little doubt as to their identity. The smoothly ovoid test with prominent apical horn, wide sutural ridges and comparatively simple plating are characteristic of this species.
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Riding et al., 2022:
Emended diagnosis: A species of Gonyaulacysta that is subpentagonal in outline, bicavate, intermediate in size, has a longitudinal L-type sulcus and a moderately large apical horn that is variable in shape.Most of the sutural features are prominent denticulate crests. Both the periphragm and endophragm are smooth.
Emended description: A species of Gonyaulacysta, subpentagonal in outline, with bicavate cyst organisation and intermediate in size. Some plate boundaries may exhibit suturocavation, especially in the precingular series. The moderately well-developed apical horn is formed by the periphragm; it may be relatively slender (delphicavate) and is always truncate distally. The endocyst may be ovoidal and may exhibit a small rounded apical protuberance. The tabulation is reflected by prominent sutural ridges or crests that vary in height and are distally denticulate. The sulcus is longitudinal, L-type. Gonal spinesmay be present on crests bounding the 1′′′′ plate; where present, they are 2–7 μm height. The ellipsoidal opisthopyle on the ps plate is normally evident. The periphragm and endophragm are both smooth.
Holotype: Specimen AO 55 of Deflandre (1938, pl. 6, 2, 3; figs. 1, 2). The sample is from the lowermost Oxfordian Marnes de Villers Formation (Quenstedtoceras mariae ammonite zone, Villers sur Mer, Calvados, northern France. Curated in the Institut de Paléontologie, Musée Nationale d'Historie Naturelle, Paris, France.
Comments: Gonyaulacysta jurassica, the type of the genus, was established by Deflandre (1938). It is easy to recognise, being bicavate, having an apical horn of moderate size, and bearing denticulate crests. However, prior to the work of Sarjeant (1982), palynologists did not distinguish the epicavate specimens characteristic of the Callovian from the bicavate forms so distinctive of the Oxfordian and Kimmeridgian. Sarjeant (1982) established Gonyaulacysta jurassica subsp. adecta for the former group, the subspecies Gonyaulacysta jurassica subsp. jurassica being automatically established for the latter group because it includes the type of the species. This finding was a genuine breakthrough, because the earliest Oxfordian range base of Gonyaulacysta jurassica subsp. jurassica (now Gonyaualacysta jurassica in the restricted sense) is an extremely useful biostratigraphical marker (Fig. 3). We propose below that Gonyaulacysta jurassica subsp. adecta should have species status. Thus, Gonyaulacysta jurassica subsp. adecta is raised to species rank, therebymaking Gonyaulacysta jurassica subsp. jurassica redundant. Gonyaulacysta jurassica sensu stricto isemended here to focus on the detailed overallmorphology, for example the suturocavation, the shape of the epicyst and the hypocystal cavation. The cavation in the epicyst of Gonyaulacysta jurassica is highly variable (Sarjeant, 1982, fig. 1). When describing the holotype of Gonyaulacysta jurassica, Sarjeant (1982, p. 14) noted that the periphragm and endophragm of the hypocyst were separated laterally, but still in contact at the antapex. He included this feature in his description of Gonyaulacysta jurassica subsp. jurassica, stating that this subspecies exhibits a partial or complete development of the hypopericoel (Sarjeant, 1982, p. 30). Poulsen (1991, p. 213) restudied the holotype and demonstrated the complete separation of the two wall layers in the antapical region and therefore, Gonyaulacysta jurassica subsp. jurassica is clearly bicavate. Poulsen (1991, p. 213) stated that the opisthopyle is in the 1′′′′ plate. The present emendation revises this to the ps plate. The emendation of Gonyaulacysta jurassica subsp. jurassica (equatingwith our concept of Gonyaualacysta jurassica) by Sarjeant (1982, p. 30) lacks key details. Gonyaulacysta jurassica is significantly variable in size, an aspect fully discussed below.
Comparison: The most similar species to Gonyaulacysta jurassica is Gonyaulacysta adecta, but the latter is consistently epicavate. Gonyaulacysta desmos, like Gonyaulacysta jurassica, has pericoels but is only partially antapically cavate (Fig. 2).
Dimensions: We have observed that the size of Gonyaulacysta jurassica significantly increased throughout its range. In order to investigate this phenomenon, material from Staffin Bay, Isle of Skye in northwestern Scotland and Lincolnshire in eastern England has been examined (Fig. 4, Table 2, Supplementary material Appendix 3, table 1). Measurements were carried out on 120 specimens from each locality, collectively covering the entire Oxfordian to lower Kimmeridgian succession. From the lower to middle Oxfordian the average length varies only slightly, decreasing from 69 μm to 67μm for the Scottish material and from 67 μm to 66 μm for the English material (Fig. 4). However, in the upper Oxfordian and Kimmeridgian, specimens of Gonyaulacysta jurassica are significantly larger. The major increase is recorded at the base of the upper Oxfordian, where the average length increases by 12 μm and 11 μm in Scotland and England respectively (Fig. 4). This was followed by a slight decrease in the lower Kimmeridgian at both localities. The results from both areas are clearly consistent with one another, suggesting that the overall trend is not arbitrary or controlled, for example, sedimentologically.
The dimensions of Gonyaulacysta jurassica studied herein, based on 120 specimens from the lower and middle Oxfordian, are: length of pericyst, 53 (67) 84; length of apical horn, 7 (12) 18; length of epipericyst, 33 (42) 58; length of hypopericyst, 13 (20) 31; length of endocyst, 33 (47) 62; width at cingulum, 36 (45) 60. The dimensions of material from the upper Oxfordian and lower Kimmeridgian, again based on 120 specimens, are: length of pericyst, 60 (77) 100; length of apical horn, 9 (14) 20; length of epipericyst, 33 (45) 60; length of hypopericyst, 13 (26) 40; length of endocyst, 40 (54) 71; width at cingulum, 33 (50) 69 (Supplementary material Appendix 3, table 1). The average length and width from the upper Oxfordian and lower Kimmeridgian compare well with the original material of Deflandre (1938, p.169–170); i.e. length of pericyst, 79; width at cingulum, 55. Deflandre (1938) also stated that the largest specimens reached 100 μm in length, whereas the smallest ones were 65 μm long in his early Oxfordian material.
Geographical and stratigraphical distribution: Gonyaulacysta jurassica occurs worldwide and is a prominent Late Jurassic species. In Europe and surrounding regions in the Northern Hemisphere, including the Arctic, it is confined to the Oxfordian and Kimmeridgian (Quenstedtoceras mariae to Aulacostephanus autissiodorensis ammonite zones; Fig. 3), and its range base and top are reliable stratigraphical markers (e.g., Feist- Burkhardt and Wille, 1992; Riding and Thomas, 1992; Poulsen and Riding, 2003). Throughout the Oxfordian and Kimmeridgian in Europe, Gonyaulacysta jurassica is normally relatively common (e.g., Brenner, 1988; Kunz, 1990; Riding and Thomas, 1997; Riding et al., 1999; Riding, 2005b), especially in the Oxfordian.
The species is also present in the Southern Hemisphere. In Australasia, Gonyaulacysta jurassica has a range of middle Bathonian to middle Kimmeridgian. It is only consistently present between the latest Bathonian and middle Oxfordian (Riding et al., 2010, fig. 12). The species does not occur in the late Bajocian to early Bathonian Wanaea verrucosa dinoflagellate cyst zone (Mantle and Riding, 2012). There are reports of sporadic specimens of Gonyaulacysta jurassica fromthe late Kimmeridgian to earliest Cretaceous in Australasia (Helby et al., 1987; Davey, 1988); however, these occurrences are believed to represent reworking.
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Gonyaulacysta jurassica (Deflandre, 1939a) Norris and Sarjeant, 1965, emend. Sarjeant, 1982b. According to Sarjeant (1982b), Gonyaulacysta jurassica has a tabulation of 2pa, 4', 2a, 6", 6c, 6"’, 1p, 1pv, 1"”. The epicyst is always considerably longer than the hypocyst and there is an epicystal pericoel below the apical horn. Sometimes there is an opisthopyle. G.jurassica is also characterised by the parasutural septa with serrated crests. The 6" plate is elongate. Size:
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