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Atopodinium polygonale
Atopodinium polygonalis, (Beju, 1983, p. 107,109,111; text-figs.3A-F,4A-F,5A-D), Masure, 1991, p. 68; Emendation: Masure, 1991, p. 68,70-71, as Atopodinium polygonale.
Originally Burtonia (an illegitimate generic name), subsequently Bejuia, thirdly (and now) Atopodinium.
Holotype: Beju, 1983, text-figs.4A-B; Masure, 1991, pl.2, figs.1,4; text-figs.3a-b; Fensome et al., 1995, figs.1-4 - p.1675; Fauconnier and Masure, 2004, pl.10, figs.8-11.
Locus typicus: Burton Cliff outcrop section, at Burton Bradstock, southeast of Bridport, Dorset, England
Stratum typicum: Early Bathonian, Zigzagiceras zigzag zone, Oppelia yeovilensis subzone
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Original description as Burtonia polygonalis: [Beju, 1983, p.107-109]:
Description:
Dorso-ventrally compressed subpolygonal proximate dinocysts with a rounded to flattened to slightly protuberant apex; antapex provided with a prominent subquadrate protuberance. Test single-layered (autocyst), laevigate, relatively thin (ca. 1 micron) with the exception of the antapex, where it thickens to form the antapical protuberance and has a coarsely granular surface. Paracingulum discernible on the ventral surface of most specimens examined, comparatively broad, strongly offset, delineated by low and narrow ridges. Its continuation on the dorsal side is less obviously expressed and appears to be strongly displaced in apical direction (Figures 4B, D, F; 5B, D), corresponding to the anterior dorsal outline of the cyst. Consequently, the dorsal side of the epicyst is considerably reduced, and the whole epicyst, which is significantly smaller than the hypocyst, is displaced ventrally. Paratabulation not fully expressed and/or determinable on the specimen recovered. However, the hypocyst appears to be formed by six paraplates delineated by low, narrow, sometimes discontinuous ridges on the ventral side, and more clearly expressed ridges on the dorsal side. Three dorsal postcingular paraplates are clearly determinable on all specimens found. The central dorsal paraplate, which may be equivalent to the 4th postcingular plate of the gonyaulacoid pattern, is comparatively large, subtrapezoidal, and extends from the paracingulum to the antapex. The two lateral dorsal postcingular plates, which may correspond to plates 3''' and 5''' of the gonyaulacoid pattern, are elongated subrectangular, somewhat narrower than the central plate. Three elongated subrectangular paraplates are discernible on the ventral postcingular side; these may correspond to paraplates 1''', 2''', 6''' of the gonyaulacid model. A slightly depressed longitudinal area between paraplates 1''' and 6''' probably indicates the parasulcus. In addition, a transversal, thickened, granular plate or "shield" is located on the ventral antapical margin of the hypocyst (Figures 4A, C, E; 5C). The epicystal paratabulation not clearly expressed on any of the specimens recovered. Archeopyle formation not clearly discernible in optical microscopy.
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Emended description:
Masure, 1991, p.70-71:
Description:
Slightly dorsoventrally compressed subspheroidal, acavate, proximate dinocyst with polygonal outline. Thin wall composed of an autophragm or of an endophragm and a periphragm in close contact, with a smooth to faintly granulate surface. The flattened epicyst is considerably smaller than the hypocyst. A sexiform gonyaulacoid thecal tabulation is inferred. The paratabulation is incompletely and weakly delineated by low ridges/septa and grana. The paratabulation is composed of 0-2 preapical(s) (P,Q), 0-?1 anterior intercalary (K), 4 apicals (1u,B,C,A), 6 precingulars (1i, 2-6), X cingulars, 5-?6 postcingulars (?Iu, II-VI), ?1 posterior intercalary (X), 1 antapical (Y) and X sulcals. The apex is slightly domed, with a small protuberance and apical paraplates are unornamented. The 6 precingulars are emphasized by accessory parasutures of the archeopyle. Two low septa mark the descending paracingulum. The ventral area is untabulated. The sulcal paraplates and the parasutures that are shared between the sulcus and the precingular (2, 1i), postcingular (Iu, II, VI), and postintercalary (X) paraplates are not expressed by surface features. Only four postcingular parasutures (II/III, III/IV, IV/V, V/VI) are erected by low septa. The smooth postcingular paraplates III, IV, V are of equal size and IV is lying below the precingular 4, the postcingular contact IV/V is aligned with the precingular 4/5. The invaginated antapical paraplate Y is broading from the dorsal surface to the ventral one (fan-shape). The dorsal contact IV/Y is shorter than the ventral contacts VI/Y, Z/Y, X/Y. The apical archeopyle is of (tA)a type, with precingular accessory parasutures. The polyplacoid, simple operculum is adnate to the sulcal ai, and the precingular 2 and 1i paraplates.
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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.
Atopodinium polygonale (Beju, 1983) Masure, 1991, emend. Masure, 1991. This differs from A.prostatum in having a shorter dorsal contact with the dorsal surface than the ventral surface. The fan shape of that invaginated antapical paraplate explains the antapical subquadrate outline of A. polygonale. Size: length 65-96 µm, width 58-94 µm.
Originally Burtonia (an illegitimate generic name), subsequently Bejuia, thirdly (and now) Atopodinium.
Holotype: Beju, 1983, text-figs.4A-B; Masure, 1991, pl.2, figs.1,4; text-figs.3a-b; Fensome et al., 1995, figs.1-4 - p.1675; Fauconnier and Masure, 2004, pl.10, figs.8-11.
Locus typicus: Burton Cliff outcrop section, at Burton Bradstock, southeast of Bridport, Dorset, England
Stratum typicum: Early Bathonian, Zigzagiceras zigzag zone, Oppelia yeovilensis subzone
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Burtonia polygonalis: [Beju, 1983, p.107-109]:
Description:
Dorso-ventrally compressed subpolygonal proximate dinocysts with a rounded to flattened to slightly protuberant apex; antapex provided with a prominent subquadrate protuberance. Test single-layered (autocyst), laevigate, relatively thin (ca. 1 micron) with the exception of the antapex, where it thickens to form the antapical protuberance and has a coarsely granular surface. Paracingulum discernible on the ventral surface of most specimens examined, comparatively broad, strongly offset, delineated by low and narrow ridges. Its continuation on the dorsal side is less obviously expressed and appears to be strongly displaced in apical direction (Figures 4B, D, F; 5B, D), corresponding to the anterior dorsal outline of the cyst. Consequently, the dorsal side of the epicyst is considerably reduced, and the whole epicyst, which is significantly smaller than the hypocyst, is displaced ventrally. Paratabulation not fully expressed and/or determinable on the specimen recovered. However, the hypocyst appears to be formed by six paraplates delineated by low, narrow, sometimes discontinuous ridges on the ventral side, and more clearly expressed ridges on the dorsal side. Three dorsal postcingular paraplates are clearly determinable on all specimens found. The central dorsal paraplate, which may be equivalent to the 4th postcingular plate of the gonyaulacoid pattern, is comparatively large, subtrapezoidal, and extends from the paracingulum to the antapex. The two lateral dorsal postcingular plates, which may correspond to plates 3''' and 5''' of the gonyaulacoid pattern, are elongated subrectangular, somewhat narrower than the central plate. Three elongated subrectangular paraplates are discernible on the ventral postcingular side; these may correspond to paraplates 1''', 2''', 6''' of the gonyaulacid model. A slightly depressed longitudinal area between paraplates 1''' and 6''' probably indicates the parasulcus. In addition, a transversal, thickened, granular plate or "shield" is located on the ventral antapical margin of the hypocyst (Figures 4A, C, E; 5C). The epicystal paratabulation not clearly expressed on any of the specimens recovered. Archeopyle formation not clearly discernible in optical microscopy.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Masure, 1991, p.70-71:
Description:
Slightly dorsoventrally compressed subspheroidal, acavate, proximate dinocyst with polygonal outline. Thin wall composed of an autophragm or of an endophragm and a periphragm in close contact, with a smooth to faintly granulate surface. The flattened epicyst is considerably smaller than the hypocyst. A sexiform gonyaulacoid thecal tabulation is inferred. The paratabulation is incompletely and weakly delineated by low ridges/septa and grana. The paratabulation is composed of 0-2 preapical(s) (P,Q), 0-?1 anterior intercalary (K), 4 apicals (1u,B,C,A), 6 precingulars (1i, 2-6), X cingulars, 5-?6 postcingulars (?Iu, II-VI), ?1 posterior intercalary (X), 1 antapical (Y) and X sulcals. The apex is slightly domed, with a small protuberance and apical paraplates are unornamented. The 6 precingulars are emphasized by accessory parasutures of the archeopyle. Two low septa mark the descending paracingulum. The ventral area is untabulated. The sulcal paraplates and the parasutures that are shared between the sulcus and the precingular (2, 1i), postcingular (Iu, II, VI), and postintercalary (X) paraplates are not expressed by surface features. Only four postcingular parasutures (II/III, III/IV, IV/V, V/VI) are erected by low septa. The smooth postcingular paraplates III, IV, V are of equal size and IV is lying below the precingular 4, the postcingular contact IV/V is aligned with the precingular 4/5. The invaginated antapical paraplate Y is broading from the dorsal surface to the ventral one (fan-shape). The dorsal contact IV/Y is shorter than the ventral contacts VI/Y, Z/Y, X/Y. The apical archeopyle is of (tA)a type, with precingular accessory parasutures. The polyplacoid, simple operculum is adnate to the sulcal ai, and the precingular 2 and 1i paraplates.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Atopodinium polygonale (Beju, 1983) Masure, 1991, emend. Masure, 1991. This differs from A.prostatum in having a shorter dorsal contact with the dorsal surface than the ventral surface. The fan shape of that invaginated antapical paraplate explains the antapical subquadrate outline of A. polygonale. Size: length 65-96 µm, width 58-94 µm.