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Aldorfia dictyota ssp. pyrum
Aldorfia dictyota ssp. pyrum, (Gitmez, 1970), Jan du Chene et al., 1986
Davies, 1983, raised this subspecies to the species level. In transferring this taxon to the genus Aldorfia Jan du Chene et al., 1986, retained it at the subspecies level. For the reason given under Aldorfia dictyota (Cookson and Eisenack, 1960) Davey, 1982, we follow Lentin and Williams, 1989, in retaining this taxon as a subspecies of Aldorfia dictyota, rather than retaining it as a subspecies of Scriniodinium dictyotum Cookson and Eisenack, 1960, as postulated by Brenner, 1988. Lentin and Williams, 1981, incorrectly changed the spelling of the taxon from pyrum to pirum". N.I.A.
Holotype: Gitmez, 1970, pl.13, figs.1-2; Jan du Chene, 1986, pl.7, figs.7-8
Locus typicus: Clay from Rhactorhynchia inconstans Bed, Ringstead Bay, Dorset (RB 219), England
Stratum typicum: Early Kimmeridgian
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Original description as Scriniodinium dictyotum ssp. pyrum: [Gitmez, 1970, p. 311-313]:
Diagnosis:
Scriniodinium dictyotum with shell elongate, roughly pear-shaped, with a strong apical horn and rounded antapex. The endophragm follows the periphragm except at the apex. The apical prominence of the endoblast is shorter and terminates in a mamelon form.
Reflected tabulation: 5", 6", 6c, 6""", 1p and 1"""".
A circular cingulum divides the theca into two unequal parts, with epitract longer than the hypotract. Sulcus approximately sigmoidal.
A precingular archaeopyle is present.
Description:
The rather large shell has a strong apical horn. The reflected tabulation is based on the alignment of some field boundaries; along the boundaries of the plates, the series of alveoli are better developed and so reflect the tabulation. Apical plate 1" is long and forms the horn, together with plate 3". Plate 2" is the smallest of the apical plates; plates 4" and 5" are rather large. The precingular plates are more or less uniform in size. Plate 3" is lost in archaeopyle formation. The cingulum is moderately wide and occupied by six plates. The sulcus extends between the apex and the antapex, in moderate breadth and approximately sigmoidal in shape. The postcingular plates are likewise large, plate 1""" being reduced to accommodate the single posterior intercalary plate 1p, The antapex is occupied by a single, quite large plate.
Dimensions:
Holotype: overall length 108 µm, breadth 74 µm; horn length 20 µm.
Range of the English specimens (5 specimens measured): overall length 108-125 µm, breadth 74-90 µm; horn length 20-30 µm.
Dimensions of the French specimen: overall length 106 µm, breadth 70 µm; horn length 14 µm.
Davies, 1983, raised this subspecies to the species level. In transferring this taxon to the genus Aldorfia Jan du Chene et al., 1986, retained it at the subspecies level. For the reason given under Aldorfia dictyota (Cookson and Eisenack, 1960) Davey, 1982, we follow Lentin and Williams, 1989, in retaining this taxon as a subspecies of Aldorfia dictyota, rather than retaining it as a subspecies of Scriniodinium dictyotum Cookson and Eisenack, 1960, as postulated by Brenner, 1988. Lentin and Williams, 1981, incorrectly changed the spelling of the taxon from pyrum to pirum". N.I.A.
Holotype: Gitmez, 1970, pl.13, figs.1-2; Jan du Chene, 1986, pl.7, figs.7-8
Locus typicus: Clay from Rhactorhynchia inconstans Bed, Ringstead Bay, Dorset (RB 219), England
Stratum typicum: Early Kimmeridgian
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Original description as Scriniodinium dictyotum ssp. pyrum: [Gitmez, 1970, p. 311-313]:
Diagnosis:
Scriniodinium dictyotum with shell elongate, roughly pear-shaped, with a strong apical horn and rounded antapex. The endophragm follows the periphragm except at the apex. The apical prominence of the endoblast is shorter and terminates in a mamelon form.
Reflected tabulation: 5", 6", 6c, 6""", 1p and 1"""".
A circular cingulum divides the theca into two unequal parts, with epitract longer than the hypotract. Sulcus approximately sigmoidal.
A precingular archaeopyle is present.
Description:
The rather large shell has a strong apical horn. The reflected tabulation is based on the alignment of some field boundaries; along the boundaries of the plates, the series of alveoli are better developed and so reflect the tabulation. Apical plate 1" is long and forms the horn, together with plate 3". Plate 2" is the smallest of the apical plates; plates 4" and 5" are rather large. The precingular plates are more or less uniform in size. Plate 3" is lost in archaeopyle formation. The cingulum is moderately wide and occupied by six plates. The sulcus extends between the apex and the antapex, in moderate breadth and approximately sigmoidal in shape. The postcingular plates are likewise large, plate 1""" being reduced to accommodate the single posterior intercalary plate 1p, The antapex is occupied by a single, quite large plate.
Dimensions:
Holotype: overall length 108 µm, breadth 74 µm; horn length 20 µm.
Range of the English specimens (5 specimens measured): overall length 108-125 µm, breadth 74-90 µm; horn length 20-30 µm.
Dimensions of the French specimen: overall length 106 µm, breadth 70 µm; horn length 14 µm.