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Chatangiella turbo

Chatangiella turbo, Harker and Sarjeant in Harker et al., 1990 ex Harker and Sarjeant, 1991

Harker and Sarjeant, 1991, validly published the species name by citing the place of lodgment of the holotype.

Holotype: Harker et al., 1990, pl.9, fig.7; text-fig.23
Locus typicus: Millwood, Manitoba, Canada
Stratum typicum: Campanian

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Original description: [Harker, Sarjeant and Caldwell, 1990, p. 118-119]

Diagnosis:
Bicavate cysts having a spindle-shaped ambitus. Periblast smooth to finely granular, thin-walled. Epitract and hypotract are of about equal size. Apical region of epitract with broad shoulders and prolonged into a long, tapering apical horn having a blunt or slightly indented distal termination. Greatest width is in the cingular region. Hypotract prolonged into a long, tapering, sharply pointed, left antapical horn, but a right antapical horn is indicated only by a slight protuberance or absent. Endoblast ovoidal, finely granular, thin-walled, its breadth greater than its length; it is closely attached to the periblast around the equatorial region. Flattened anterior and posterior margins abut a large apical and a smaller antapical pericoel. A broad, slightly laevorotatory cingulum is represented by low, granulate ridges or close-set rows of granules, broken by gaps into elements that indicate the presence of seven precingular and five postcingular paraplates; ventral displacement is less than one cingulum width. A posteriorly divergent and anteriorly convergent sulcus is indicated by low, narrow thickenings of the periphragm on the ventral surface of the hypotract of the periblast.
Archaeopyle intercalary (I/3I,2a/la-3a), perioperculum omegaform to broadly hexagonal in shape. Opercular paraplates normally remain attached after opening.

Description:
The long, tapering antapical horn is only slightly offset from the apical-antapical axis of the cyst, giving it a distinctive spindle shape. The right antapical horn may be indicated by a small protuberance of the periphragm (Pl. 9, Fig. 6) or may be altogether lacking.
The epitract has broad shoulders and the apical horn has an indented distal termination (Pl. 9, Fig. 8). The periphragm is smooth to finely granulate and less than 0.5 µm thick; the endophragm is 0.5-1.0 µm thick, with a finely granulate ornament (relief less than 0.5 µm).
The apical and antapical flattening of the endoblast is very marked.
The rows of granules that mark the cingular margins are 1-3 µm wide, 0.5-1 µm high; their division into units, indicating the presence of seven precingular and five postcingular paraplates, is well seen on several specimens.
The archaeopyle is formed by the displacement of a large omegaform to broadly hexagonal paraplate (2a) in the periblast and of three paraplates in the endoblast (1a-3a). All paraplates involved in archaeopyle formation remain attached, though the perioperculum is frequently folded.

Dimensions:
Holotype: overall length 107 µm, breadth 64 µm; length of endoblast 46 µm; apical horn 12 µm; left antapical 21 µm; cingulum width 6µm; transverse peripyle ratio 2.4. Range of 32 measurable specimens: overall length 89-138 µm, breadth 50-83 µm; length of endoblast 43-77 µm; apical horn 12-18 µm; left antapical 17-31 µm; cingulum width 5-9 µm; transverse peripyle ratio 1.1-2.4 µm.

Affinities: (p. 120):
This species is similar to C.granulifera, but differs in its lighter granulation and extreme development of the left antapical horn, producing a spindle-shaped ambitus. Trithyrodinium druggii Stone 1973, differs in having a rounded, scabrate endoblast with tufted apical and antapical regions, the three-paraplate peripyle (1a-3a) and no observable cingulum or sulcus.
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