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Chatangiella niiga

Chatangiella niiga, Vozzhennikova, 1967; Emend. Lentin and Vozzhennikova, 1990

Taxonomic junior synonym: Chatangiella cassidea, according to Lentin and Vozzhennikova (1990, p.45) - however, Lebedeva in Ilyina et al. (1994, p.69) retained Chatangiella cassidea.

Holotype: Vozzhennikova 1967, pl.56, fig.1, pl.57, fig.1; Lentin and Vozzhennikova, 1990, pl.5, figs.1-2; text-fig.20
Locus typicus: Khatanga depression, W. Siberia
Stratum typicum: Santonian

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Original description: [Vozzhennikova, 1967, p. 129]: (Translation: Lees in Sarjeant, 1971):

Description:
Epitheca on a level with the upper edge of the internal body slightly or strongly tapering and broadening again. In the middle of the uncurved or slightly concave apical margin of the theca there is a conical, bluntly rounded, apical horn. The hypotheca lies on the level of the lower boundary of the internal body, also tapers and then widens again, thus forming a trapeziform or retangular antapical end to the theca. The antapical end is bluntly or acutely rounded and somewhat extend to form an antapical horn.
The internal body is oval, slightly compressed along the longitudinal axis and closely applied to the convexly curved lateral walls of the theca. The surface of the internal body is smooth and dotted. The transverse furrow is shallow, equatorial and slightly spiral. The longitudinal furrow reaches the posterior margin. The thecal surface is granular with sparsely arranged, short spines which lie in the middle of the theca and on the margin of the transverse furrow. The pylome is polygonal, with its broader retangular part lying in the expanded apical portion of the theca and its narrower part extending into the tapering portion of the theca. The pylome reaches the upper edge of the internal body and may even extend towards the transverse furrow.

Dimensions (in µm):
holotype - length of theca: 113.4, width: 59.4. Length of internal body: 45.9, width of transverse furrow about 3.
In other specimens: length 108-121.5, breadth: 59.4-62.1, length of internal body 44.9-54 and width of transverse furrow: 3-8.

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Emended description:

Lentin and Vozzhennikova, 1990, p. 45-46:

Description:
Cyst shape elongate rectangular with a short apical horn between well developed shoulders and a convex paracingular region; antapex nearly flat with two poorly developed antapical horns, occasionally the left antapical horn may be more developed; endocyst round to roundly rectangular in outline, dividing the cyst equally; bicavate.
Periphragm smooth to finely granulose with randomly located rare small spines; endocyst finely granulose with thickened apical and antapical margins within the epi- and hypopericoel, thickenings appear to be fibrous or sponge-like.
Paratabulation peridinioid, indicated by archeopyle and paracingulum only;
the periarcheopyle is iso-omegaform with the 4" - 2a parasuture about one third the length of the 2a - 3" parasuture, operculum remains attached along the 4" - 2a parasuture; the endoarcheopyle is 3I or undeveloped; an opisthopyle may be formed by an arcuate suture on the mid-ventral surface of the hypocyst.
The paracingulum is outlined by parallel ridges of occasional spines, faintly pentapartite.
Parasulcus indicated by a shallow depression on the hypocyst.

Dimensions:
Holotype, length of pericyst 113 µm, width 59 µm, length of endocyst 46 µm, width of paracingulum about 3 µm;
range, length 108-121.5 µm, breadth 59-62 µm, length of endocyst 45-54 µm and width of paracingulum 3-8 µm.
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