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Canningia transitoria
Canningia transitoria, Stover and Helby, 1987
Holotype: Stover and Helby, 1987, figs.3A-E
Locus typicus: Perth Basin, W Australia
Stratum typicum: Barremian-Early Aptian
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Original description: [Stover and Helby, 1987, p. 262-263]:
Description:
Cysts proximate, lenticular, with rounded cingular and antapical protrusions. Left antapical protrusion consistently longer than the right, which may be reduced or absent. Apical margin obtusely angular.
Autophragm about 1 µm thick, smooth or faintly ornamented, bearing relatively widely spaced (10-18 µm apart), discontinuous septa or arcuate rows of processes together with isolated processes. Septa and processes generally penitabular, isolated processes appear intratabular; septa and processes 1.5-3 µm wide, flared and simply branched near their distal ends, supporting a thin (less than 1 µm), continuous, punctoreticulate ectophragm or one interrupted and differentially perforated, i.e., some areas may be more coarsely perforate than others. Perforations circular to irregularly polygonal in outline, from less than 0.5 µm to 5 µm in diameter, tending to be absent or less numerous in pandasutural areas. Separation of the ectophragm and autophragm greatest at the cingular and antapical protrusions (10-15 µm), may be as little as 5 µm in other areas.
Archeopyle apical, type [tA], with a zigzag principal suture and an offset parasulcal notch. Operculum free.
Paratabulation indicated minimally by archeopyle, cingular bulges and discontinuous seemingly parasutural features; indicated more completely by perforate to lace-like patches of the ectophragm separated by pandasuturate bands of variable width (Fig.3F,G). Outlines of the ectophragmal patches simulating those of the paraplates. Paratabulation formula: 4', 6'', X-3c, 6''', 1p, 1'''', Xs or as.
Paracingulum expressed by lateral bulges, and additionally on some specimens by a transverse ectophragmal band which on the ventral surface may be broken into segments. Ends of the paracingulum offset by approximately three times its width.
Parasulcus sigmoid, its anterior position marked by the parasulcal notch and by the narrow anterior sulcal paraplate on some specimens; posterior part generally slightly wider than the anterior part and offset to the right. Specimens 114-125 µm wide at the cingular bulges; 10 specimens measured. No complete specimens found.
Paratabulation: The presence of 4 apical paraplates is inferred from the notches along the archeopyle and operculum margins, but the shape of the constituent paraplates was not determined. In the precingular series, the relatively large, 6-sided, asymmetrically gabled 6'' occupies a significant part of the midventral surface (Fig.4A). Other gabled paraplates in this series include 1" and 3" . The 5" may be gabled also, but we could not verify this. In general, individual cingular paraplates are not differentiated, however, the somewhat arcuate 6c and parts of 1c and 5c are discernible on occasional specimens. Paraplate 1''' is smaller than others in the postcingular series and only the anterior part of 6''' is clearly outlined. The posterior part of this paraplate is apparently obscured by the posterior concavity, or is simply not expressed. The as, 1''' and 1p paraplates are essentially in line longitudinally (Fig.4A,B), and the last is significantly larger than the others. Only the anterior dorsal part of 1'''' has been observed, with the outline of the rest of the paraplate hidden on specimens seen in dorsal ventral views.
Affinities:
Canningia transitoria differs from C. reticulata Cookson & Eisenack emend. Helby (1987) in having more widely separated wall layers and considerably fewer supporting structures within the ectocoel. Canningia grandis Helby (1987) also has more numerous supporting structures within the ectocoel and possesses a uniformly reticulate ectophragmal mesh which is much coarser than that on specimens of C. transitoria. Evidently the ectophragm on C. grandis does not break into paraplate related areas separated by pandasuturate features. Canningia sp. cf. C. transitoria (Fig.13A-C) is transitional between C. transitoria and C. grandis.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Canningia transitoria Stover and Helby, 1987d, has widely spaced (10-18 µm apart), discontinuous septa or arcuate rows of processes together with isolated processes. Ectophragm usually punctoreticulate. Marshall (1990) disproved Duxbury’s (1983) argument that Canninginopsis is ceratioid, by showing that it has the typical sexiform tabulation and six cingular plates. He labelled the sulcal plates and noted the presence along some plate boundaries of two rows rather than one row of grana.
Holotype: Stover and Helby, 1987, figs.3A-E
Locus typicus: Perth Basin, W Australia
Stratum typicum: Barremian-Early Aptian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Stover and Helby, 1987, p. 262-263]:
Description:
Cysts proximate, lenticular, with rounded cingular and antapical protrusions. Left antapical protrusion consistently longer than the right, which may be reduced or absent. Apical margin obtusely angular.
Autophragm about 1 µm thick, smooth or faintly ornamented, bearing relatively widely spaced (10-18 µm apart), discontinuous septa or arcuate rows of processes together with isolated processes. Septa and processes generally penitabular, isolated processes appear intratabular; septa and processes 1.5-3 µm wide, flared and simply branched near their distal ends, supporting a thin (less than 1 µm), continuous, punctoreticulate ectophragm or one interrupted and differentially perforated, i.e., some areas may be more coarsely perforate than others. Perforations circular to irregularly polygonal in outline, from less than 0.5 µm to 5 µm in diameter, tending to be absent or less numerous in pandasutural areas. Separation of the ectophragm and autophragm greatest at the cingular and antapical protrusions (10-15 µm), may be as little as 5 µm in other areas.
Archeopyle apical, type [tA], with a zigzag principal suture and an offset parasulcal notch. Operculum free.
Paratabulation indicated minimally by archeopyle, cingular bulges and discontinuous seemingly parasutural features; indicated more completely by perforate to lace-like patches of the ectophragm separated by pandasuturate bands of variable width (Fig.3F,G). Outlines of the ectophragmal patches simulating those of the paraplates. Paratabulation formula: 4', 6'', X-3c, 6''', 1p, 1'''', Xs or as.
Paracingulum expressed by lateral bulges, and additionally on some specimens by a transverse ectophragmal band which on the ventral surface may be broken into segments. Ends of the paracingulum offset by approximately three times its width.
Parasulcus sigmoid, its anterior position marked by the parasulcal notch and by the narrow anterior sulcal paraplate on some specimens; posterior part generally slightly wider than the anterior part and offset to the right. Specimens 114-125 µm wide at the cingular bulges; 10 specimens measured. No complete specimens found.
Paratabulation: The presence of 4 apical paraplates is inferred from the notches along the archeopyle and operculum margins, but the shape of the constituent paraplates was not determined. In the precingular series, the relatively large, 6-sided, asymmetrically gabled 6'' occupies a significant part of the midventral surface (Fig.4A). Other gabled paraplates in this series include 1" and 3" . The 5" may be gabled also, but we could not verify this. In general, individual cingular paraplates are not differentiated, however, the somewhat arcuate 6c and parts of 1c and 5c are discernible on occasional specimens. Paraplate 1''' is smaller than others in the postcingular series and only the anterior part of 6''' is clearly outlined. The posterior part of this paraplate is apparently obscured by the posterior concavity, or is simply not expressed. The as, 1''' and 1p paraplates are essentially in line longitudinally (Fig.4A,B), and the last is significantly larger than the others. Only the anterior dorsal part of 1'''' has been observed, with the outline of the rest of the paraplate hidden on specimens seen in dorsal ventral views.
Affinities:
Canningia transitoria differs from C. reticulata Cookson & Eisenack emend. Helby (1987) in having more widely separated wall layers and considerably fewer supporting structures within the ectocoel. Canningia grandis Helby (1987) also has more numerous supporting structures within the ectocoel and possesses a uniformly reticulate ectophragmal mesh which is much coarser than that on specimens of C. transitoria. Evidently the ectophragm on C. grandis does not break into paraplate related areas separated by pandasuturate features. Canningia sp. cf. C. transitoria (Fig.13A-C) is transitional between C. transitoria and C. grandis.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Canningia transitoria Stover and Helby, 1987d, has widely spaced (10-18 µm apart), discontinuous septa or arcuate rows of processes together with isolated processes. Ectophragm usually punctoreticulate. Marshall (1990) disproved Duxbury’s (1983) argument that Canninginopsis is ceratioid, by showing that it has the typical sexiform tabulation and six cingular plates. He labelled the sulcal plates and noted the presence along some plate boundaries of two rows rather than one row of grana.