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Ctenidodinium panneum
Ctenidodinium panneum (Norris, 1965) Lentin and Williams, 1973
Now Dichadogonyaulax?. Originally Leptodinium, subsequently Dichadogonyaulax, thirdly Ctenidodinium, fourthly (and now) Dichadogonyaulax?.
Stover and Evitt, 1978, concurred with Lentin and Williams, 1973. Sarjeant, 1975, and Benson, 1985, retained this species in Dichadogonyaulax.
Holotype: Norris, 1986, figs.10-12
Locus typicus: West Weare Cliff, Isle of Portland
Stratum typicum: Kimmeridgian-Portlandian
Original diagnosis: Norris, 1965, p. 796: Leptodinium panneum
Midbody ovoid, oblate, with helds disposed according to the following scheme: 4", 6"", 5""", 1p, 1"""". Fields bordered by high spiny flanges. Ventral area depressed with a distinct posterior field and less clear median helds, anterior end not sharply delimited from 1". Girdle spiralled, posterior border with a high-spiny flange, anterior border not distincfly raised. probably approxlmately delimited by a suture along which an epithecal archeopyle opens. Shell is of organic material, about 0.75 Ám thick, irregularly intrapunctate.
Original description: Norris, 1965, p. 796-797: Leptodinium panneum
Apical series consists of a pair of elongated fields (1" and 4") and a pair of roughly equidimensional fields (2" and 3"). The elongated fields are each about 20 Ám long in dorso-ventral direction and 10 Ám, wide in lateral direction 1" is a direct continuation of the anterior end of the ventral area and is usually delimited from it by a constriction of the field borders at the antapical end of 1". Precingular series 20 to 30 Ám high, 6"" usually smaller than the others. Postcingular series mostly larger than the precingular series; 1""" is very small and 5""" is slightly larger, but neither is prominent owing to the much larger fields 2""", 3""", and 4""" which are about 40 Á high. 3""" is very large, occupying much of the dorsal face and displacing the antapical field toward the ventral side. 1"""" is rectangular. 10 to 25 Ám wide, markedly displaced toward the ventral side.
Ventral area clearly depressed, extending and widening from the first apical field, where it is 1 to 2 Ám wide, to the antapical field. where it may reach about 15 Ám, in width. Posterior ventral field clearly delimited and bounded by 1"""", 1p, and 5""". Median ventral fields indistinctly divided by impersistent ridges extending up to the posterior border of the anterior end of the girdle. The exact number of median ventral fields is not known with certainty, but there are at least four and possibly five. The entire ventral area is bounded by spiny flanges, which may be higher (up to 14 Ám) and carry more irregularly branching spines than the adjacent field and girdle borders.
Girdle undivided 4 to 7 Ám, wide; anterior-posterior separation just over one girdle width; lateral separation 5 to 15 Ám; girdle floor may be slightly raised, bordered posteriorly by a spiny flange. Flange 6 to 12 Ám high, 0.5 Ám, to 1 Ám wide carrying on the undivided lower third a series of spines spaced 3 to 5 Ám apart. Spines undivided or simply bifurcate, some in surface view appearing to have trunks rather wider than the flanges on which they stand. Anterior girdle border not distinct unless, as is usual, the archeopyle is developed. Anterior border also delimited by the raised floor of the girdle. Field borders are similar to the posterior girdle border.
Shell infrapunctate to microreticulate, punctae and lumina up to 1 Á in diameter.
Margin of epithecal archeopyle clean-cut. running parallel to the posterior girdle border or occasionally along a slight but regular zigzag course, presumably approximately delimiting the anterior edge of the girdle region. Operculum integral consisting of 10 fields (1"-4" and 1""-6""), attached. Archeopyle first opens on the dorsal surface and hinges on the ventral area. Sometimes the operculum is completely free of the remainder of the shell, in which case the archeopyle margin cuts straight across the ventral area. The operculum is interpreted as attached because the ventral area apparently shows some resistance to rupture.
Dimensions: Midbody apex to antapex 44-55 Ám (holotype 45), equatorial diameter 57-68 Ám, (holotype 57 Ám).
Affinities:
Norris, 1986, p. 798: Leptodinium panneum
Gonyaulax ornata (Eisenack) Klement (1960) is similar to Leptodinium panneum but is distinguished from it by the non-oblate nature of the shell, by the presence of 6 postcingular fields, by the lack division of the median ventral area, and by the clear delimitation of the anterior end of the ventral area from the first apical field.
Now Dichadogonyaulax?. Originally Leptodinium, subsequently Dichadogonyaulax, thirdly Ctenidodinium, fourthly (and now) Dichadogonyaulax?.
Stover and Evitt, 1978, concurred with Lentin and Williams, 1973. Sarjeant, 1975, and Benson, 1985, retained this species in Dichadogonyaulax.
Holotype: Norris, 1986, figs.10-12
Locus typicus: West Weare Cliff, Isle of Portland
Stratum typicum: Kimmeridgian-Portlandian
Original diagnosis: Norris, 1965, p. 796: Leptodinium panneum
Midbody ovoid, oblate, with helds disposed according to the following scheme: 4", 6"", 5""", 1p, 1"""". Fields bordered by high spiny flanges. Ventral area depressed with a distinct posterior field and less clear median helds, anterior end not sharply delimited from 1". Girdle spiralled, posterior border with a high-spiny flange, anterior border not distincfly raised. probably approxlmately delimited by a suture along which an epithecal archeopyle opens. Shell is of organic material, about 0.75 Ám thick, irregularly intrapunctate.
Original description: Norris, 1965, p. 796-797: Leptodinium panneum
Apical series consists of a pair of elongated fields (1" and 4") and a pair of roughly equidimensional fields (2" and 3"). The elongated fields are each about 20 Ám long in dorso-ventral direction and 10 Ám, wide in lateral direction 1" is a direct continuation of the anterior end of the ventral area and is usually delimited from it by a constriction of the field borders at the antapical end of 1". Precingular series 20 to 30 Ám high, 6"" usually smaller than the others. Postcingular series mostly larger than the precingular series; 1""" is very small and 5""" is slightly larger, but neither is prominent owing to the much larger fields 2""", 3""", and 4""" which are about 40 Á high. 3""" is very large, occupying much of the dorsal face and displacing the antapical field toward the ventral side. 1"""" is rectangular. 10 to 25 Ám wide, markedly displaced toward the ventral side.
Ventral area clearly depressed, extending and widening from the first apical field, where it is 1 to 2 Ám wide, to the antapical field. where it may reach about 15 Ám, in width. Posterior ventral field clearly delimited and bounded by 1"""", 1p, and 5""". Median ventral fields indistinctly divided by impersistent ridges extending up to the posterior border of the anterior end of the girdle. The exact number of median ventral fields is not known with certainty, but there are at least four and possibly five. The entire ventral area is bounded by spiny flanges, which may be higher (up to 14 Ám) and carry more irregularly branching spines than the adjacent field and girdle borders.
Girdle undivided 4 to 7 Ám, wide; anterior-posterior separation just over one girdle width; lateral separation 5 to 15 Ám; girdle floor may be slightly raised, bordered posteriorly by a spiny flange. Flange 6 to 12 Ám high, 0.5 Ám, to 1 Ám wide carrying on the undivided lower third a series of spines spaced 3 to 5 Ám apart. Spines undivided or simply bifurcate, some in surface view appearing to have trunks rather wider than the flanges on which they stand. Anterior girdle border not distinct unless, as is usual, the archeopyle is developed. Anterior border also delimited by the raised floor of the girdle. Field borders are similar to the posterior girdle border.
Shell infrapunctate to microreticulate, punctae and lumina up to 1 Á in diameter.
Margin of epithecal archeopyle clean-cut. running parallel to the posterior girdle border or occasionally along a slight but regular zigzag course, presumably approximately delimiting the anterior edge of the girdle region. Operculum integral consisting of 10 fields (1"-4" and 1""-6""), attached. Archeopyle first opens on the dorsal surface and hinges on the ventral area. Sometimes the operculum is completely free of the remainder of the shell, in which case the archeopyle margin cuts straight across the ventral area. The operculum is interpreted as attached because the ventral area apparently shows some resistance to rupture.
Dimensions: Midbody apex to antapex 44-55 Ám (holotype 45), equatorial diameter 57-68 Ám, (holotype 57 Ám).
Affinities:
Norris, 1986, p. 798: Leptodinium panneum
Gonyaulax ornata (Eisenack) Klement (1960) is similar to Leptodinium panneum but is distinguished from it by the non-oblate nature of the shell, by the presence of 6 postcingular fields, by the lack division of the median ventral area, and by the clear delimitation of the anterior end of the ventral area from the first apical field.