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Heslertonia heslertonensis
Heslertonia heslertonensis (Neale and Sarjeant, 1962, p.440–441, pl.19, fig.5; pl.20, fig.5; text-figs.1a–b) Sarjeant, 1966b, p.133. Emendation: Duxbury, 1980, p.124, as Heslertonia heslertonensis.
Originally Gonyaulax, subsequently (and now) Heslertonia
Holotype: Neale and Sarjeant, 1962, pl.19, fig.5, text-fig.1
Paratype: Neale and Sarjeant, 1962
Locus typicus: Speeton Clay, Heslterton, England
Stratum typicum: Hauterivian-Barremian
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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.
Heslertonia heslertonensis (Neale and Sarjeant, 1962) Sarjeant, 1966b, emend. Duxbury, 1980. According to Duxbury (1980), Heslertonia heslertonensis has a spheroidal to ovoidal main body with high parasutural crests, which outline a typically gonyaulacacean paratabulation. These portions of the parasutural crests very close to the main body frequently have vacuolar structures and the distal crestal margins have very narrow, linear thickenings. Typically, epicystal crests are lower than hypocystal crests. The archeopyle is epicystal with the epicyst usually remaining attached in the parasulcal area. Size: overall length 64-67 µm, overall width 64 µm, central body length 36.5-40.5 µm, width 37.5-38 µm.
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Original diagnosis: Neale and Sarjeant, 1962, p. 43-44: Gonyaulax heslertonense
A species of fossil Conyaulax having a theca of rounded pntagonal outline, with epithecn conicnl and hypotheca truncated conical. Tabulations 5', 6'', 6-?7''', ?1p, 1''''. Transverse furrow strongly spiral, laevo-rotatory, divided by low ridges into sections (?6). Crests on plate and furrow boundaries high and delicate.
Original description: Neale and Sarjeant, 1962, p.45: Gonyaulax heslertonense
Shell deep yellow in colour, not granulate or punctate. Crests very pale yellow, delicate and frequently folded: in part or constantly, they bifurcate distally in T or Y fashion and have denticulate or smooth edges. Five apical plates; plate 1' is elongate, its anterior portion occupying the apex. Six pre-equatorial plates, plate 1 being somewhat reduced: no anterior intercalary plates present. The transverse furrow is strongly spiral, its two ends differing in antero-posterior position by more than three times the furrow's breadth. The longitudinal furrow is of moderate breadth and extends from the antapical plate to meet plate 1' halfway up the epitheca. Structure of the hypotheca less clear: apparently seven post-equatorial plates, with plates 1''' and 7''' reduced: a posterior intercalary plate present, posterior to plate 1'''. A single polygonal plate occupies the antapex.
Dimensions: Overall length 64 Ám, breadth 64 Ám: shell length 36 Ám, breadth 37.5 Ám.
Emended Diagnosis: Duxbury, 1980, p. 124
A species of Heslertonia having a spheroidal to ovoidal main body bearing high parasutural crests which outline a typically gonyaulacacean paratabulation pattern. Those portions of the parasutural crests very close to the main body frequently exhibit vacuolar structures and the distal crestal margins have very narrow, linear thickenings. Typically epicystal, crests are lower than hypocystal ones. The archaeopyle is epicystal with the epicyst usually remaining attached in the parasulcal area.
Affinities:
Neale and Sarjeant, 1962, p. 45: Gonyaulax heslertonense
This species differs from all deseribed fossil species of Gonyaulax in the character of its crests. A resemblance exists to the genus Pterodinium Eisenack 1958, which also has high crests and whose tabulation has not been specified: however, G. heslertonense differs in outline and crest character from all described species and forms of Eisenack's genus.
Sarjeant 1966b, p. 133: Forms closely comparable to this species have been figured and described from the Middle Cretaceous of Australia as Cymatiosphaera striata Eisenack and Cookson (1960: 9, Pl.3, figs.10,11). Both forms have in common high, striate crests: the figures suggest that the Australian species also has a cingulum and a determinable tabulation. A full restudy of the Australian
specimens appears necessary to determine whether H.heslertonensis and C.striata are congeneric or conspecific; should the latter prove to be the case, the earlier name striata would have priority.
Duxbury 1980, p. 124: In exhibiting an epicystal archaeopyle, in frequently having vacuolar structures along proximal crestal margins and in its overall size, H. heslertonensis is very similar both to Avellodinium falsificum Duxbury, 1977 and Callaiosphaeridium asymmetricum (Deflandre and Courteville, 1939) Davey and Williams, 1966, especially to the latter. Further, the presence of high
parasutural crests (albeit irregular) in Callaiosphaeridium trycherium emphasis the closeness of Callaiosphaeridium and Heslertonia.
Heilmann-Clausen in Heilmann-Clausen and Costa, 1989, p. 472-473, pl. 9, fig.1-6: aff. Heslertonia heslertonensis
A dinoflagellate cyst with a small sphaerical, not always clearly visible, central body ornamented with high parasutural septa. The distal edges of the septa usually support narrow bands with denticulate margins, giving a T-shape to the septa in cross section, like in H. heslertonensis. An archaeopyle has not been identified.
The similarity with H. heslertonensis is probably superficial, as there is no evidence of an epicystal archaeopyle.
Originally Gonyaulax, subsequently (and now) Heslertonia
Holotype: Neale and Sarjeant, 1962, pl.19, fig.5, text-fig.1
Paratype: Neale and Sarjeant, 1962
Locus typicus: Speeton Clay, Heslterton, England
Stratum typicum: Hauterivian-Barremian
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Heslertonia heslertonensis (Neale and Sarjeant, 1962) Sarjeant, 1966b, emend. Duxbury, 1980. According to Duxbury (1980), Heslertonia heslertonensis has a spheroidal to ovoidal main body with high parasutural crests, which outline a typically gonyaulacacean paratabulation. These portions of the parasutural crests very close to the main body frequently have vacuolar structures and the distal crestal margins have very narrow, linear thickenings. Typically, epicystal crests are lower than hypocystal crests. The archeopyle is epicystal with the epicyst usually remaining attached in the parasulcal area. Size: overall length 64-67 µm, overall width 64 µm, central body length 36.5-40.5 µm, width 37.5-38 µm.
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Original diagnosis: Neale and Sarjeant, 1962, p. 43-44: Gonyaulax heslertonense
A species of fossil Conyaulax having a theca of rounded pntagonal outline, with epithecn conicnl and hypotheca truncated conical. Tabulations 5', 6'', 6-?7''', ?1p, 1''''. Transverse furrow strongly spiral, laevo-rotatory, divided by low ridges into sections (?6). Crests on plate and furrow boundaries high and delicate.
Original description: Neale and Sarjeant, 1962, p.45: Gonyaulax heslertonense
Shell deep yellow in colour, not granulate or punctate. Crests very pale yellow, delicate and frequently folded: in part or constantly, they bifurcate distally in T or Y fashion and have denticulate or smooth edges. Five apical plates; plate 1' is elongate, its anterior portion occupying the apex. Six pre-equatorial plates, plate 1 being somewhat reduced: no anterior intercalary plates present. The transverse furrow is strongly spiral, its two ends differing in antero-posterior position by more than three times the furrow's breadth. The longitudinal furrow is of moderate breadth and extends from the antapical plate to meet plate 1' halfway up the epitheca. Structure of the hypotheca less clear: apparently seven post-equatorial plates, with plates 1''' and 7''' reduced: a posterior intercalary plate present, posterior to plate 1'''. A single polygonal plate occupies the antapex.
Dimensions: Overall length 64 Ám, breadth 64 Ám: shell length 36 Ám, breadth 37.5 Ám.
Emended Diagnosis: Duxbury, 1980, p. 124
A species of Heslertonia having a spheroidal to ovoidal main body bearing high parasutural crests which outline a typically gonyaulacacean paratabulation pattern. Those portions of the parasutural crests very close to the main body frequently exhibit vacuolar structures and the distal crestal margins have very narrow, linear thickenings. Typically epicystal, crests are lower than hypocystal ones. The archaeopyle is epicystal with the epicyst usually remaining attached in the parasulcal area.
Affinities:
Neale and Sarjeant, 1962, p. 45: Gonyaulax heslertonense
This species differs from all deseribed fossil species of Gonyaulax in the character of its crests. A resemblance exists to the genus Pterodinium Eisenack 1958, which also has high crests and whose tabulation has not been specified: however, G. heslertonense differs in outline and crest character from all described species and forms of Eisenack's genus.
Sarjeant 1966b, p. 133: Forms closely comparable to this species have been figured and described from the Middle Cretaceous of Australia as Cymatiosphaera striata Eisenack and Cookson (1960: 9, Pl.3, figs.10,11). Both forms have in common high, striate crests: the figures suggest that the Australian species also has a cingulum and a determinable tabulation. A full restudy of the Australian
specimens appears necessary to determine whether H.heslertonensis and C.striata are congeneric or conspecific; should the latter prove to be the case, the earlier name striata would have priority.
Duxbury 1980, p. 124: In exhibiting an epicystal archaeopyle, in frequently having vacuolar structures along proximal crestal margins and in its overall size, H. heslertonensis is very similar both to Avellodinium falsificum Duxbury, 1977 and Callaiosphaeridium asymmetricum (Deflandre and Courteville, 1939) Davey and Williams, 1966, especially to the latter. Further, the presence of high
parasutural crests (albeit irregular) in Callaiosphaeridium trycherium emphasis the closeness of Callaiosphaeridium and Heslertonia.
Heilmann-Clausen in Heilmann-Clausen and Costa, 1989, p. 472-473, pl. 9, fig.1-6: aff. Heslertonia heslertonensis
A dinoflagellate cyst with a small sphaerical, not always clearly visible, central body ornamented with high parasutural septa. The distal edges of the septa usually support narrow bands with denticulate margins, giving a T-shape to the septa in cross section, like in H. heslertonensis. An archaeopyle has not been identified.
The similarity with H. heslertonensis is probably superficial, as there is no evidence of an epicystal archaeopyle.