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Gonyaulacysta dualis
Gonyaulacacysta dualis (Brideaux and Fisher, 1976) Stover and Evitt, 1978
Originally Psaligonyaulax, subsequently (and now) Gonyaulacysta.
Tax. jr. synonym of Gonyaulacysta jurassica (Deflandre, 1938) Norris and Sarjeant, 1965, according to Sarjeant, 1982. Jan du Chene 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 Chene et al., 1986. Therefore, Gonyaulacysta dualis, by implication, is a tax. jr. synonym of Scriniodinium ceratophorum.
Holotype: Brideaux and Fisher, 1976, pl. 1, fig. 4-5; Jan du Chene et al., 1986, pl.37, fig.11-12
Locus typicus: Elf Horton River, N Canada
Stratum typicum: Late Oxfordian-Late Kimmeridgian
Original description: Brideaux and Fisher, 1976, p. 18: Psaligonyaulax dualis Diagnosis: Periblast elongate, typically twice as long as broad, with sligthly 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. Archaeopyle 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 1pr, 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.
Dimensions: Holotype: Periblast length 125 µm, width 95µm; endoblast length 74 µm. Range: Periblast length 93-135 µm; apical horn 20-33 µm; endoblast length 63-100 µm; endoblast horn 3-9 µm; periblast width 40-83µm. 25 specimens measured.
For an elaborate description see Brideaux and Fisher, 1976, p. 18-19
Affinities:
Brideaux and Fisher, 1976, p. 19 : Psaligonyaulax dualis
P. dualis differs from previously published species of the genus in the following ways: from P. deflanfrei Sarjeant by its larger size, more prominent apical horn, rhombic endoblast and details of tabulation; from P. apatela (Cookson and Eisenack) Sarjeant in overal 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 in shape, form of sutures, details of tabulation, and other features. P. dualis bears a superficial similarity to Gonyaulacacysta jurassica (Deflandre) Norris and Sarjeant, 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 speicmens of G. jurassica; P. dualis has well-developed apical and antapical pericoels; specimens with a pronounced apical pericoel assigned to G. jurassica by Sarjeant differ in that the pericoel is formed by broadening of the apical horn at its base. P. 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.
Originally Psaligonyaulax, subsequently (and now) Gonyaulacysta.
Tax. jr. synonym of Gonyaulacysta jurassica (Deflandre, 1938) Norris and Sarjeant, 1965, according to Sarjeant, 1982. Jan du Chene 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 Chene et al., 1986. Therefore, Gonyaulacysta dualis, by implication, is a tax. jr. synonym of Scriniodinium ceratophorum.
Holotype: Brideaux and Fisher, 1976, pl. 1, fig. 4-5; Jan du Chene et al., 1986, pl.37, fig.11-12
Locus typicus: Elf Horton River, N Canada
Stratum typicum: Late Oxfordian-Late Kimmeridgian
Original description: Brideaux and Fisher, 1976, p. 18: Psaligonyaulax dualis Diagnosis: Periblast elongate, typically twice as long as broad, with sligthly 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. Archaeopyle 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 1pr, 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.
Dimensions: Holotype: Periblast length 125 µm, width 95µm; endoblast length 74 µm. Range: Periblast length 93-135 µm; apical horn 20-33 µm; endoblast length 63-100 µm; endoblast horn 3-9 µm; periblast width 40-83µm. 25 specimens measured.
For an elaborate description see Brideaux and Fisher, 1976, p. 18-19
Affinities:
Brideaux and Fisher, 1976, p. 19 : Psaligonyaulax dualis
P. dualis differs from previously published species of the genus in the following ways: from P. deflanfrei Sarjeant by its larger size, more prominent apical horn, rhombic endoblast and details of tabulation; from P. apatela (Cookson and Eisenack) Sarjeant in overal 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 in shape, form of sutures, details of tabulation, and other features. P. dualis bears a superficial similarity to Gonyaulacacysta jurassica (Deflandre) Norris and Sarjeant, 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 speicmens of G. jurassica; P. dualis has well-developed apical and antapical pericoels; specimens with a pronounced apical pericoel assigned to G. jurassica by Sarjeant differ in that the pericoel is formed by broadening of the apical horn at its base. P. 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.