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Dichadogonyaulax norrisii
Dichadogonyaulax norrisii (Pocock, 1972) Sarjeant, 1975
Originally Leptodinium, subsequently Dichadogonyaulax, thirdly Ctenidodinium, fourthly Korystocysta.
Taxonomic senior synonym: Gonyaulax (now Korystocysta) pachyderma, according to Benson (1985, p.154).
Taxonomic junior synonym: Dichadogonyaulax (subsequently Korystocysta) kettonensis, by implication in Conway (1990, p.35), who considered Korystocysta kettonensis to be the senior name - however, Lentin and Williams (1993, p.374) retained Dichadogonyaulax (as Korystocysta) kettonensis.
Holotype: Pocock, 1972, pl.24, fig.9; Jansonius, 1986, pl.2, figs.6-8; text-fig.5
Locus typicus: Imperial Tidewater Wapalla, W Canada
Stratum typicum: Callovian
Original description: Pocock, 1972, p.92: Leptodinium norrisii
Theca more or less isodiametric; both hypotheca and epitheca more or less hemispherical; apical horn reduced or absent; represented by the small plate 4"; slightly helicoidal equatorial girdle well developed; forms a band of weakness along which the theca splits into two hemispheres (epithecal archeopyle with a simple operculum); longitudinal furrow more or less same width on epitheca and hypotheca; tabulation 4", 1a, 6", 5""", 1""""; sutures well delineated; cingular plates shield-shaped, each with a very narrow ridge developed on the face of the plate parallel to the suture (see diagram); sutures mark lines of weakness and isolated plates readily split off from the theca resulting in the presence of loose plates in most preparations; thecal wall about 2.0 Ám thick; infrapunctate; internally smooth; external surface punctate; lines of the sutures, particularly around the equatorial girdle and the 1"""" plate, ornamented with crowded, very fine, pinnate spines about 1.0-5.0 Ám Iong and 0.2Á--1.0 Ám wide, spaced about 1.0 Ám apart; colour pale yellow; length of theca 60.0 (89.0) 126.0 Ám; equatorial diameter 66.0 (87.0) 110.0 Ám.
Supplemental description: Jansonius, 1986, p.205-206
(Holotype) Cyst ca. 80 Ám, consisting of epicyst and hypocyst separated along the anterior border of the cingulum, slightly rotated (by about 30¦) with regard to each other, and upon compression the epicyst partly clasping the left lateral cingular area of the hypocyst. Wall single-layered, in hypocyst ca 1 Ám thick, in epicyst slightly thinner, with a granular aspect and pitted surface, yellow.
Paratabulation marked by parasutural rows of very small (0.25 x 1 Ám) to larger (0.5-1 Ám thick, up to 5 Ám high) spines and spinules, often intermixed and closely spaced. The spines along 1"""" are firm and show well on the outline; the spinules on both margins of the cingulum are uniformly 1.5 Ám diameter. The margins of 3" are delineated by a mixture of shorter (2 Ám) and taller (4 Ám) spines, the taller ones being interconnected by trabeculate loops of wall tissue of ca 0.5 Ám diameter; some of these taller spines branch distally. The preapical plate is marked by a tuft of spines and spinules (2-3 Ám tall). There is little evidence of penitabular ridges paralleling paraplate boundaries, other than a faint ridge on 5""". There are no accessory splits between plates along the epitractal archeopyle. Because of the position of the hypocyst, the exact paratabulation of the sulcal area could not be determined. The epicyst has an unusually narrow sulcal area, which is not distinctly delineated.
Affinities:
Jansonius, 1986, p. 205: Other specimens on the type slide #404 show variable amounts of penitabular sculpture in the form of single or double ridges, interrupted ridges, rows of spines or granules or groups of granules, all more or less parallel to plate boundaries and spaced at some 2-4 Ám (resembling thecal growth lines). Also, a few specimens have much more solid spines (1.5-2 x 1 Ám) incorporated in the sutural ridges. Most of these specimens consist only of an epitheca or a hypotheca. The holotype is a complete specimen, but in its appearance not very typical for the species.
Pocock"s fig. 12 is an incomplete epicyst in apical aspect; part of the base of 2" in lacking, and the cingular region of 3" and 4" is folded over. A small preapical, at the end of the split cutting through 1", is thickened, and two small triangular intercalaries occur at the junction of 2", 3", 3" and 4". It is here reillustrated as Plate 2, fig. 9-10. Another epicyst (404-1-112 x 43.8), in antapical aspect, shows similar plating, with a thickened preapical and intercalaries at the intersections of 2", 3", 3" and 4". In this specimen (here illustrated as Plate 2, fig.11) penitabular or intratabular ridges are clearly developed showing the characteristic pattern of "growth lines."
The paratabulation of D. norrisii is remarkably close to that of D. schizoblatum Norris 1965, especially as regards the intercalary plates of the epicyst. D. norrisii may differ in the tendency to develop various amounts of penitabular sculpture, and in having spinose plate boundaries; it appears to lack the ventral paratabulation as indicated by Norris for C. schizoblatum. Korystocysta has a more elongate shape, and an apical horn.
Originally Leptodinium, subsequently Dichadogonyaulax, thirdly Ctenidodinium, fourthly Korystocysta.
Taxonomic senior synonym: Gonyaulax (now Korystocysta) pachyderma, according to Benson (1985, p.154).
Taxonomic junior synonym: Dichadogonyaulax (subsequently Korystocysta) kettonensis, by implication in Conway (1990, p.35), who considered Korystocysta kettonensis to be the senior name - however, Lentin and Williams (1993, p.374) retained Dichadogonyaulax (as Korystocysta) kettonensis.
Holotype: Pocock, 1972, pl.24, fig.9; Jansonius, 1986, pl.2, figs.6-8; text-fig.5
Locus typicus: Imperial Tidewater Wapalla, W Canada
Stratum typicum: Callovian
Original description: Pocock, 1972, p.92: Leptodinium norrisii
Theca more or less isodiametric; both hypotheca and epitheca more or less hemispherical; apical horn reduced or absent; represented by the small plate 4"; slightly helicoidal equatorial girdle well developed; forms a band of weakness along which the theca splits into two hemispheres (epithecal archeopyle with a simple operculum); longitudinal furrow more or less same width on epitheca and hypotheca; tabulation 4", 1a, 6", 5""", 1""""; sutures well delineated; cingular plates shield-shaped, each with a very narrow ridge developed on the face of the plate parallel to the suture (see diagram); sutures mark lines of weakness and isolated plates readily split off from the theca resulting in the presence of loose plates in most preparations; thecal wall about 2.0 Ám thick; infrapunctate; internally smooth; external surface punctate; lines of the sutures, particularly around the equatorial girdle and the 1"""" plate, ornamented with crowded, very fine, pinnate spines about 1.0-5.0 Ám Iong and 0.2Á--1.0 Ám wide, spaced about 1.0 Ám apart; colour pale yellow; length of theca 60.0 (89.0) 126.0 Ám; equatorial diameter 66.0 (87.0) 110.0 Ám.
Supplemental description: Jansonius, 1986, p.205-206
(Holotype) Cyst ca. 80 Ám, consisting of epicyst and hypocyst separated along the anterior border of the cingulum, slightly rotated (by about 30¦) with regard to each other, and upon compression the epicyst partly clasping the left lateral cingular area of the hypocyst. Wall single-layered, in hypocyst ca 1 Ám thick, in epicyst slightly thinner, with a granular aspect and pitted surface, yellow.
Paratabulation marked by parasutural rows of very small (0.25 x 1 Ám) to larger (0.5-1 Ám thick, up to 5 Ám high) spines and spinules, often intermixed and closely spaced. The spines along 1"""" are firm and show well on the outline; the spinules on both margins of the cingulum are uniformly 1.5 Ám diameter. The margins of 3" are delineated by a mixture of shorter (2 Ám) and taller (4 Ám) spines, the taller ones being interconnected by trabeculate loops of wall tissue of ca 0.5 Ám diameter; some of these taller spines branch distally. The preapical plate is marked by a tuft of spines and spinules (2-3 Ám tall). There is little evidence of penitabular ridges paralleling paraplate boundaries, other than a faint ridge on 5""". There are no accessory splits between plates along the epitractal archeopyle. Because of the position of the hypocyst, the exact paratabulation of the sulcal area could not be determined. The epicyst has an unusually narrow sulcal area, which is not distinctly delineated.
Affinities:
Jansonius, 1986, p. 205: Other specimens on the type slide #404 show variable amounts of penitabular sculpture in the form of single or double ridges, interrupted ridges, rows of spines or granules or groups of granules, all more or less parallel to plate boundaries and spaced at some 2-4 Ám (resembling thecal growth lines). Also, a few specimens have much more solid spines (1.5-2 x 1 Ám) incorporated in the sutural ridges. Most of these specimens consist only of an epitheca or a hypotheca. The holotype is a complete specimen, but in its appearance not very typical for the species.
Pocock"s fig. 12 is an incomplete epicyst in apical aspect; part of the base of 2" in lacking, and the cingular region of 3" and 4" is folded over. A small preapical, at the end of the split cutting through 1", is thickened, and two small triangular intercalaries occur at the junction of 2", 3", 3" and 4". It is here reillustrated as Plate 2, fig. 9-10. Another epicyst (404-1-112 x 43.8), in antapical aspect, shows similar plating, with a thickened preapical and intercalaries at the intersections of 2", 3", 3" and 4". In this specimen (here illustrated as Plate 2, fig.11) penitabular or intratabular ridges are clearly developed showing the characteristic pattern of "growth lines."
The paratabulation of D. norrisii is remarkably close to that of D. schizoblatum Norris 1965, especially as regards the intercalary plates of the epicyst. D. norrisii may differ in the tendency to develop various amounts of penitabular sculpture, and in having spinose plate boundaries; it appears to lack the ventral paratabulation as indicated by Norris for C. schizoblatum. Korystocysta has a more elongate shape, and an apical horn.