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Psaligonyaulax dualis
Psaligonyaulax dualis Brideaux and Fisher, 1976
NOW Gonyaulacysta. Originally Psaligonyaulax, subsequently (and now) Gonyaulacysta.
Tax. jr. synonym of Gonyaulacysta jurassica (Deflandre, 1938) Norris and Sarjeant, 1965, according to Sarjeant, 1982; however, Jan du Chêne et al., 1986 retained Gonyaulacysta dualis as a separate species.
Tax. sr. synonym of Psaligonyaulax australica Cookson and Eisenack, 1982, according to Brenner, 1988, which species is also a tax. jr. synonym of Scriniodinium? ceratophorum Cookson and Eisenack, 1960, according to Jan du Chêne et al., 1986. Therefore, Psaligonyaulax dualis, by implication, is a tax. jr. synonym of Scriniodinium ceratophorum.
Holotype: Brideaux and Fisher, 1976, pl.1, figs.4-5
Locus typicus: Gilmore Lake Member, District of Franklin, Canada
Stratum typicum: Late Oxfordian-Late Kimmeridgian
Original diagnosis: Brideaux and Fisher, 1976, p. 18-19
Periblast elongate, typically twice as long as broad, with slightly tapering apical horn; endoblast rhomboid with a short apical prominence and rounded antapex. Antapical breach typically present in the periblast, rarely closed by a moderately bulging antapical prominence. Periblast and endoblast in close contact only at latitude of cingulum, resulting in formation of distinct apical and antapical pericoels. Surface of periphragm and endophragm smooth or, rarely, scabrate. Archeopyle in each layer formed by loss of third reflected precingular plate; opercula separate and detached, elongate. Periblast forms sutural crests which outline a reflected tabulation of lpr, 4" 6", 6c, 5"""-?6""", 1p, 1""""; crests variable, entire to denticulate, rarely spiny. Cingulum displaced up to two cingular widths, distinct; reflected sulcal tabulation absent but sulcal region distinct.
Original desciption: Brideaux and Fisher, 1976, p. 19
The periblast is elongate, the length from one and one-half to two and one-half times the width. Maximum width of the periblast occurs at the latitude of the cingulum. The periblast is prolonged apically into a slightly tapered and slender horn, which is capped by a small pre-apical reflected plate. The apical horn represents from one-fifth to one-third, typically one-fourth of the total periblast length. Antapically the periblast exhibits a quadrangular opening at the position of the reflected antapical plate. A few specimens (Pl. 1, fig. 12) bear a moderately bulging antapical prominence and the opening is absent. The commonly occurring antapical breach is thus interpreted as resulting from the ?mechanical loss of this antapical prominence. The endoblast is somewhat rhomboidal in general shape. The epithecal part is generally triangular and bears a short, rounded apical prominence, 3-9µm in length. The hypothecal part is more hemispherical and is rounded antapically. The periblast and endoblast are in close contact only at the latitude of the cingulum; consequently, extensive apical and antapical pericoels result. The apical prominence of the endoblast extends into the apical pericoel. The antapical pericoel is generally open to the exterior. The surfaces of the periphragm and endophragm are smooth or, more rarely, scabrate. Folded portions of the periblast are projected to form the sutural crests. The archeopyle is precingular in position on the periblast and endoblast and in both cases is formed by loss of reflected plate 3". The opercula are separate and usually detached, but may remain in place, especially in the case of the endoperculum. Opercula are commonly found in the pericoel and less commonly in the endocoel. Opercula are distinctly longer than broad, rounded anteriorly and flattened posteriorly. The sutural crests are 3-4µm high and may be entire, variably denticulate or, more rarely, bear spinose ornament. The denticulate processes are connected basally and are 1-2µm high; the spiny elements may reach 4µm in height and generally are discrete but densely spaced along the crests. The sutural crests outline a reflected tabulation pattern of 1pr, 4", 6", 6c, 5"""-?6""", 1p, 1"""". All reflected plates of the apical series, but especially 1", are elongated and terminated anteriorly by the reflected pre-apical plate. Reflected plates of the precingular series and plate 3"""-5""" of the post- cingular series also are elongate. Reflected plates 2""" and 6""" are smaller and more equidimensional.
Plate 1""" may not be distinct, merging with the sulcal region; where 1""" is distinct, it is very small and triangular. Reflected intercalary plates were not observed.
The sutural crests outline a cingulum and six reflected cingular plates. The cingulum is about 7-9Á wide and its ventral terminations are displaced from one and one-half to two cingular widths. The sulcus is poorly defined by the periphery of the other reflected plates and is without distinct reflected sulcal tabulation. The sulcus widens posteriorly to meet the antapical breach, and narrows anteriorly where it is terminated by reflected apical plate 1". There is no distinct boundary between the
anterior termination of the sulcus and the posterior termination of plate 1". The anterior portion of the sulcus begins where the sutural crests outlining reflected plate 1" end abruptly. Dimensions - Periblast length, 93-135 µm; apical horn, 20-33 µm; endoblast length, 63-100 µm; endoblast horn, 3-9 µm; periblast width, 40-83 µm.
Brideaux and Fisher, 1976, p. 19: Psaligonyaulax dualis differs from previously published species of the genus in the following ways: from P. deflandrei Sarjeant (1966, p. 137) by its larger size, more prominent apical horn, rhombic endoblast, and details of tabulation; from P. apatela (Cookson and Eisenack) Sarjeant
(1969, p. 15) in overall shape, greater overall length and length of apical horn, type of sutural crests, shape of the endophragm, and details of tabulation; and from P. simplicia (Cookson and Eisenack) Sarjeant (1969, p. 15) in shape, form of sutures, details of tabulation, and other features. Psaligonyaulax dualis bears a superficial similarity to Gonyaulacysta jurassica (Deflandre) Norris and Sarjeant (1965, p. 65), but differs in at least four features. The size of the periblast and endoblast is generally larger, the smaller specimens of P. dualis overlapping only with the largest specimens of G. jurassica; P. dualis has well-developed apical and antapical pericoels; specimens with a pronounced apical pericoel assigned
to G. jurassica by Sarjeant (1972, p. 10, 11, Pl. 1, figs. 2, 4) differ in that the pericoel is formed by broadening of the apical horn at its base. Psaligonyaulax dualis has a consistently well-developed antapical breach in the periblast, and more rarely, an antapical bulge. Finally, the endoblast of P. dualis exhibits a consistently rhombic
outline. Several authors have illustrated specimens assigned to Gonyaulacysta jurassica subsp. longicornis Lentin and Williams, 1973 (p. 62), which appear closely comparable to Psaligonyaulax dualis based on examination of the figures.
NOW Gonyaulacysta. Originally Psaligonyaulax, subsequently (and now) Gonyaulacysta.
Tax. jr. synonym of Gonyaulacysta jurassica (Deflandre, 1938) Norris and Sarjeant, 1965, according to Sarjeant, 1982; however, Jan du Chêne et al., 1986 retained Gonyaulacysta dualis as a separate species.
Tax. sr. synonym of Psaligonyaulax australica Cookson and Eisenack, 1982, according to Brenner, 1988, which species is also a tax. jr. synonym of Scriniodinium? ceratophorum Cookson and Eisenack, 1960, according to Jan du Chêne et al., 1986. Therefore, Psaligonyaulax dualis, by implication, is a tax. jr. synonym of Scriniodinium ceratophorum.
Holotype: Brideaux and Fisher, 1976, pl.1, figs.4-5
Locus typicus: Gilmore Lake Member, District of Franklin, Canada
Stratum typicum: Late Oxfordian-Late Kimmeridgian
Original diagnosis: Brideaux and Fisher, 1976, p. 18-19
Periblast elongate, typically twice as long as broad, with slightly tapering apical horn; endoblast rhomboid with a short apical prominence and rounded antapex. Antapical breach typically present in the periblast, rarely closed by a moderately bulging antapical prominence. Periblast and endoblast in close contact only at latitude of cingulum, resulting in formation of distinct apical and antapical pericoels. Surface of periphragm and endophragm smooth or, rarely, scabrate. Archeopyle in each layer formed by loss of third reflected precingular plate; opercula separate and detached, elongate. Periblast forms sutural crests which outline a reflected tabulation of lpr, 4" 6", 6c, 5"""-?6""", 1p, 1""""; crests variable, entire to denticulate, rarely spiny. Cingulum displaced up to two cingular widths, distinct; reflected sulcal tabulation absent but sulcal region distinct.
Original desciption: Brideaux and Fisher, 1976, p. 19
The periblast is elongate, the length from one and one-half to two and one-half times the width. Maximum width of the periblast occurs at the latitude of the cingulum. The periblast is prolonged apically into a slightly tapered and slender horn, which is capped by a small pre-apical reflected plate. The apical horn represents from one-fifth to one-third, typically one-fourth of the total periblast length. Antapically the periblast exhibits a quadrangular opening at the position of the reflected antapical plate. A few specimens (Pl. 1, fig. 12) bear a moderately bulging antapical prominence and the opening is absent. The commonly occurring antapical breach is thus interpreted as resulting from the ?mechanical loss of this antapical prominence. The endoblast is somewhat rhomboidal in general shape. The epithecal part is generally triangular and bears a short, rounded apical prominence, 3-9µm in length. The hypothecal part is more hemispherical and is rounded antapically. The periblast and endoblast are in close contact only at the latitude of the cingulum; consequently, extensive apical and antapical pericoels result. The apical prominence of the endoblast extends into the apical pericoel. The antapical pericoel is generally open to the exterior. The surfaces of the periphragm and endophragm are smooth or, more rarely, scabrate. Folded portions of the periblast are projected to form the sutural crests. The archeopyle is precingular in position on the periblast and endoblast and in both cases is formed by loss of reflected plate 3". The opercula are separate and usually detached, but may remain in place, especially in the case of the endoperculum. Opercula are commonly found in the pericoel and less commonly in the endocoel. Opercula are distinctly longer than broad, rounded anteriorly and flattened posteriorly. The sutural crests are 3-4µm high and may be entire, variably denticulate or, more rarely, bear spinose ornament. The denticulate processes are connected basally and are 1-2µm high; the spiny elements may reach 4µm in height and generally are discrete but densely spaced along the crests. The sutural crests outline a reflected tabulation pattern of 1pr, 4", 6", 6c, 5"""-?6""", 1p, 1"""". All reflected plates of the apical series, but especially 1", are elongated and terminated anteriorly by the reflected pre-apical plate. Reflected plates of the precingular series and plate 3"""-5""" of the post- cingular series also are elongate. Reflected plates 2""" and 6""" are smaller and more equidimensional.
Plate 1""" may not be distinct, merging with the sulcal region; where 1""" is distinct, it is very small and triangular. Reflected intercalary plates were not observed.
The sutural crests outline a cingulum and six reflected cingular plates. The cingulum is about 7-9Á wide and its ventral terminations are displaced from one and one-half to two cingular widths. The sulcus is poorly defined by the periphery of the other reflected plates and is without distinct reflected sulcal tabulation. The sulcus widens posteriorly to meet the antapical breach, and narrows anteriorly where it is terminated by reflected apical plate 1". There is no distinct boundary between the
anterior termination of the sulcus and the posterior termination of plate 1". The anterior portion of the sulcus begins where the sutural crests outlining reflected plate 1" end abruptly. Dimensions - Periblast length, 93-135 µm; apical horn, 20-33 µm; endoblast length, 63-100 µm; endoblast horn, 3-9 µm; periblast width, 40-83 µm.
Brideaux and Fisher, 1976, p. 19: Psaligonyaulax dualis differs from previously published species of the genus in the following ways: from P. deflandrei Sarjeant (1966, p. 137) by its larger size, more prominent apical horn, rhombic endoblast, and details of tabulation; from P. apatela (Cookson and Eisenack) Sarjeant
(1969, p. 15) in overall shape, greater overall length and length of apical horn, type of sutural crests, shape of the endophragm, and details of tabulation; and from P. simplicia (Cookson and Eisenack) Sarjeant (1969, p. 15) in shape, form of sutures, details of tabulation, and other features. Psaligonyaulax dualis bears a superficial similarity to Gonyaulacysta jurassica (Deflandre) Norris and Sarjeant (1965, p. 65), but differs in at least four features. The size of the periblast and endoblast is generally larger, the smaller specimens of P. dualis overlapping only with the largest specimens of G. jurassica; P. dualis has well-developed apical and antapical pericoels; specimens with a pronounced apical pericoel assigned
to G. jurassica by Sarjeant (1972, p. 10, 11, Pl. 1, figs. 2, 4) differ in that the pericoel is formed by broadening of the apical horn at its base. Psaligonyaulax dualis has a consistently well-developed antapical breach in the periblast, and more rarely, an antapical bulge. Finally, the endoblast of P. dualis exhibits a consistently rhombic
outline. Several authors have illustrated specimens assigned to Gonyaulacysta jurassica subsp. longicornis Lentin and Williams, 1973 (p. 62), which appear closely comparable to Psaligonyaulax dualis based on examination of the figures.