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Chatangiella hexacalpis
Chatangiella hexacalpis, 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.8, fig.11; text-figs.22A-B
Locus typicus: Mowbray, Manitoba, Canada
Stratum typicum: Late Campanian
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Original description: [Harker, Sarjeant and Caldwell, 1990, p. 117-118]
Diagnosis:
Bicavate cysts with a subpentagonal ambitus.
Periblast smooth to finely granular, thin-walled, tapering into an apical horn, the apical region and pericoel having almost the shape of an isosceles triangle; sometimes with feebly developed "shoulders". Tip of apical horn indented. Antapical pericoel broad-based, giving rise to two unequal antapical horns: a long, sharply tapering and pointed left and a shorter subconical right horn, with a pronounced concavity between. Greatest ambital width in the cingular region. Epitract and hypotract of about equal size. Endoblast smooth and thin-walled, with a broadly subhexagonal ambitus; its anterior and posterior margins are flattened and it is attached laterally to the periphragm.
A broad, slightly laevorotatory cingulum is indicated by two low, parallel, dorsally partite ridges; ventral displacement is less than half the cingulum"s width.
Sulcus indicated by two low, posteriorly divergent and anteriorly convergent ridges on the ventral surface.
Parasutures indicated in some specimens by low, narrow and discontinuous ridges, delimiting a paratabulation of 4", 3a, 7", 0c, 7""", 2"""".
Archaeopyle intercalary (I/I, 2a/2a; or occasionally I/3I, 2a/la/3a); perioperculum standard hexagonal to omegaform, remaining attached along its posterior margin. The endoperculum usually remains in place, only slight displacement of the paraplates being observable.
Description:
The thinness of the phragma is a distinctive feature of this species; even in the equatorial region of contact between periphragm and endophragm, the combined thickness of both phragma layers is less than 0.5 µm. As a consequence the specimens do not stain readily. The epitract is conical in most specimens, terminating in a horn from which it is not distinctly separable; its shoulders are, at best, poorly developed. The endoblast is equatorially positioned and has an asymmetrically hexagonal ambitus; flattened margins abut the apical and antapical pericoels and rounded angles contact the periblast at its widest part in the cingular region (Text-fig. 22).
Surface ornament is largely absent, save for occasional fine granules of less than 0.5 µm relief. Low ridge-like thickenings of the periphragm indicate the cingulum and sulcus and occasionally also indicate parasutures, outlining four apical, three anterior intercalary, seven precingular and five postcingular paraplates (Pl. 8, Fig. 16). The cingular ridges are continuous, save in the sulcal region and on either side of the mid-dorsal region (Pl. 8, Fig. 11; Text-fig. 22).
Dimensions:
Holotype: overall length 108 µm, breadth 72 µm, length of endoblast 57 µm, apical horn 8 µm, left antapical horn 20 µm, right antapical horn 7 µm, cingulum width 6 µm, transverse peripyle index 0.47, transverse peripyle ratio 0.71.
Range of 207 measurable specimens: periblast length 64-116 µm, mean 89 µm; breadth 40-83 µm, mean 65 µm; length of endoblast 28-47 µm, mean 43 µm; apical horn 6-9 µm, mean 7 µm; length of left antapical horn 10-26 µm, mean 13 µm; length of right antapical horn 1-9 µm, mean 3 µm; cingulum width 4-8 µm, mean 6 µm; transverse peripyle index 0.44-0.51, mean 0.48; transverse peripyle ratio 0.71-1.10, mean 0.79.
Affinities:
C. ditissima, C. diapertura (McInyre1975) Lentin and Williams 1976 and C. porosa Marshall 1988 are similar in shape to this species: C. ditissima differs in its larger overall size and has a larger apical horn, well-developed epitractal shoulders, postulate cingular ridges and a more quadrate antapex; C. biapertura differs in possessing a thicker phragma, a subspherical endoblast and an opisthopyle; and C. porosa has distinct "shoulders" on its apical pericoel, plus a markedly larger archaeopyle. The specimen illustrated by Leopold and Tschudy (1965, Fig. 189) appears similar in size and overall morphology to those observed.
Harker and Sarjeant, 1991, validly published the species name by citing the place of lodgment of the holotype.
Holotype: Harker et al., 1990, pl.8, fig.11; text-figs.22A-B
Locus typicus: Mowbray, Manitoba, Canada
Stratum typicum: Late Campanian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Harker, Sarjeant and Caldwell, 1990, p. 117-118]
Diagnosis:
Bicavate cysts with a subpentagonal ambitus.
Periblast smooth to finely granular, thin-walled, tapering into an apical horn, the apical region and pericoel having almost the shape of an isosceles triangle; sometimes with feebly developed "shoulders". Tip of apical horn indented. Antapical pericoel broad-based, giving rise to two unequal antapical horns: a long, sharply tapering and pointed left and a shorter subconical right horn, with a pronounced concavity between. Greatest ambital width in the cingular region. Epitract and hypotract of about equal size. Endoblast smooth and thin-walled, with a broadly subhexagonal ambitus; its anterior and posterior margins are flattened and it is attached laterally to the periphragm.
A broad, slightly laevorotatory cingulum is indicated by two low, parallel, dorsally partite ridges; ventral displacement is less than half the cingulum"s width.
Sulcus indicated by two low, posteriorly divergent and anteriorly convergent ridges on the ventral surface.
Parasutures indicated in some specimens by low, narrow and discontinuous ridges, delimiting a paratabulation of 4", 3a, 7", 0c, 7""", 2"""".
Archaeopyle intercalary (I/I, 2a/2a; or occasionally I/3I, 2a/la/3a); perioperculum standard hexagonal to omegaform, remaining attached along its posterior margin. The endoperculum usually remains in place, only slight displacement of the paraplates being observable.
Description:
The thinness of the phragma is a distinctive feature of this species; even in the equatorial region of contact between periphragm and endophragm, the combined thickness of both phragma layers is less than 0.5 µm. As a consequence the specimens do not stain readily. The epitract is conical in most specimens, terminating in a horn from which it is not distinctly separable; its shoulders are, at best, poorly developed. The endoblast is equatorially positioned and has an asymmetrically hexagonal ambitus; flattened margins abut the apical and antapical pericoels and rounded angles contact the periblast at its widest part in the cingular region (Text-fig. 22).
Surface ornament is largely absent, save for occasional fine granules of less than 0.5 µm relief. Low ridge-like thickenings of the periphragm indicate the cingulum and sulcus and occasionally also indicate parasutures, outlining four apical, three anterior intercalary, seven precingular and five postcingular paraplates (Pl. 8, Fig. 16). The cingular ridges are continuous, save in the sulcal region and on either side of the mid-dorsal region (Pl. 8, Fig. 11; Text-fig. 22).
Dimensions:
Holotype: overall length 108 µm, breadth 72 µm, length of endoblast 57 µm, apical horn 8 µm, left antapical horn 20 µm, right antapical horn 7 µm, cingulum width 6 µm, transverse peripyle index 0.47, transverse peripyle ratio 0.71.
Range of 207 measurable specimens: periblast length 64-116 µm, mean 89 µm; breadth 40-83 µm, mean 65 µm; length of endoblast 28-47 µm, mean 43 µm; apical horn 6-9 µm, mean 7 µm; length of left antapical horn 10-26 µm, mean 13 µm; length of right antapical horn 1-9 µm, mean 3 µm; cingulum width 4-8 µm, mean 6 µm; transverse peripyle index 0.44-0.51, mean 0.48; transverse peripyle ratio 0.71-1.10, mean 0.79.
Affinities:
C. ditissima, C. diapertura (McInyre1975) Lentin and Williams 1976 and C. porosa Marshall 1988 are similar in shape to this species: C. ditissima differs in its larger overall size and has a larger apical horn, well-developed epitractal shoulders, postulate cingular ridges and a more quadrate antapex; C. biapertura differs in possessing a thicker phragma, a subspherical endoblast and an opisthopyle; and C. porosa has distinct "shoulders" on its apical pericoel, plus a markedly larger archaeopyle. The specimen illustrated by Leopold and Tschudy (1965, Fig. 189) appears similar in size and overall morphology to those observed.