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Rhynchodiniopsis palla
Rhynchidiniopsis palla (Sarjeant, 1966) Sarjeant, 1982
Now Cribroperidinium. Originally Gonyaulacysta, subsequently Millioudodinium, thirdly Rhynchodiniopsis, fourthly (and now) Cribroperidinium.
Holotype: Sarjeant, 1966, pl.13, figs.3,4; Jan du Chêne et al., 1986, pl.27, figs.15-17
Locus typicus: Speeton Clay, Heslerton, England
Stratum typicum: Barremian
Original diagnosis: Sarjeant, 1966, p. 113: Gonyaulacysta palla
A Gonyaulacysta with almost spherical theca and prominent apical horn. Tabulation 4", 1a, 6"", ?6c, ?7""", 1p, 1""""; plate boundaries demarcated by crests formed of very short spines arising from low ridges. Plate 1" elongate, occupying anterior prolongation of sulcus and relatively large; plate 4" small, occupying horn tip. Sulcus and cingulum of moderate breadth. Plate 1""" small and quadrate: posterior intercalary plate correspondingly small. Plate 2""" somewhat larger than plate 1""", but remaining markedly smaller than other postcingular plates. Number of postcingular plates probably seven, but presence of crest between plates 4""" and 5""" not confirmed.
Dimensions: holotype: overall length 62 µm, length of horn, 10 µm; overall breadth 50 µm; breadth of cingulum c.4 µm. Range of dimensions observed; overall lengths 60-64 µm, overall breadths 46-52 µm.
Original description: Sarjeant, 1966, p. 114: Gonyaulacysta palla
Theca spherical, relatively thin-walled and apparently fragile; of some 20 specimens seen, all had suffered damage additional to archaeopyle formation. The holotype is the best-preserved, but nonetheless shows a tear in median ventral position. Surface densely granular, the granulation rendering the low crests difficult to distinguish in lateral positions.
Apical horn slender and relatively long, accounting for about 1/6th of the thecal length. Its tip is formed by plate 4", its base by plates 1" to 3". Six precingular plates, with plate 6" reduced to accommodate the anterior intercalary plate. Either six or seven postcingular plates; presence of the presumed boundary between plates 4" and 5" could not be completely verified in any specimen seen, through a combination of damage and unfortunate orientation. Plates 1""" and 1p are both small: plate 2""" is also reduced and does not have a boundary with the antapical plate. The antapical plate has the appearance of being inclined towards the ventral face, but this may simply result from compression. The cingulum is of moderate breadth and strongly laevorotatory, its two ends differing in antero-posterior position by about one and a half times its breadth. The number of cingular plates is doubtful. The sulcus is short and of moderate breadth. All specimens seen have a precingular archaeopyle, formed by loss of plate 3".
Affinities:
Sarjeant, 1966, p. 114: Gonyaulacysta palla
In its combination of overall morphology and tabulation, Gonyaulacysta palla differs from all other described species. The most closely similar species is G. ambigua (Deflandre), which has a similarly spherical shape and crests of comparable character, but differs in having no comparable apical horn and a different ventral tabulation.
Now Cribroperidinium. Originally Gonyaulacysta, subsequently Millioudodinium, thirdly Rhynchodiniopsis, fourthly (and now) Cribroperidinium.
Holotype: Sarjeant, 1966, pl.13, figs.3,4; Jan du Chêne et al., 1986, pl.27, figs.15-17
Locus typicus: Speeton Clay, Heslerton, England
Stratum typicum: Barremian
Original diagnosis: Sarjeant, 1966, p. 113: Gonyaulacysta palla
A Gonyaulacysta with almost spherical theca and prominent apical horn. Tabulation 4", 1a, 6"", ?6c, ?7""", 1p, 1""""; plate boundaries demarcated by crests formed of very short spines arising from low ridges. Plate 1" elongate, occupying anterior prolongation of sulcus and relatively large; plate 4" small, occupying horn tip. Sulcus and cingulum of moderate breadth. Plate 1""" small and quadrate: posterior intercalary plate correspondingly small. Plate 2""" somewhat larger than plate 1""", but remaining markedly smaller than other postcingular plates. Number of postcingular plates probably seven, but presence of crest between plates 4""" and 5""" not confirmed.
Dimensions: holotype: overall length 62 µm, length of horn, 10 µm; overall breadth 50 µm; breadth of cingulum c.4 µm. Range of dimensions observed; overall lengths 60-64 µm, overall breadths 46-52 µm.
Original description: Sarjeant, 1966, p. 114: Gonyaulacysta palla
Theca spherical, relatively thin-walled and apparently fragile; of some 20 specimens seen, all had suffered damage additional to archaeopyle formation. The holotype is the best-preserved, but nonetheless shows a tear in median ventral position. Surface densely granular, the granulation rendering the low crests difficult to distinguish in lateral positions.
Apical horn slender and relatively long, accounting for about 1/6th of the thecal length. Its tip is formed by plate 4", its base by plates 1" to 3". Six precingular plates, with plate 6" reduced to accommodate the anterior intercalary plate. Either six or seven postcingular plates; presence of the presumed boundary between plates 4" and 5" could not be completely verified in any specimen seen, through a combination of damage and unfortunate orientation. Plates 1""" and 1p are both small: plate 2""" is also reduced and does not have a boundary with the antapical plate. The antapical plate has the appearance of being inclined towards the ventral face, but this may simply result from compression. The cingulum is of moderate breadth and strongly laevorotatory, its two ends differing in antero-posterior position by about one and a half times its breadth. The number of cingular plates is doubtful. The sulcus is short and of moderate breadth. All specimens seen have a precingular archaeopyle, formed by loss of plate 3".
Affinities:
Sarjeant, 1966, p. 114: Gonyaulacysta palla
In its combination of overall morphology and tabulation, Gonyaulacysta palla differs from all other described species. The most closely similar species is G. ambigua (Deflandre), which has a similarly spherical shape and crests of comparable character, but differs in having no comparable apical horn and a different ventral tabulation.