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Invertocysta tabulata
Invertocysta tabulata Edwards, 1984
Holotype: Edwards, 1984, pl.3, figs.3A-B; text-figs.6A-B; Fensome et al., 1995, figs.1-4 - p.1837.
Stratum typicum: Middle-Late Miocene
Locus typicus: DSDP Site 555, E North Atlantic
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Invertocysta tabulata Edwards, 1984. Cyst cavate, endocyst with apical boss, periphragm and endophragm in contact ventrally. Well developed parasutural ridges, with paratabulation: 4', 6", 4-6c, 5-6"’, 1p, 1"”, ?3-5s. Nearly all of the dorsal area of the periphragm represents 3" and is missing. Size: Overall 63-113 µm, endocyst 37-58 µm long.
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Original description: Edwards, 1984, p. 585
Diagnosis: Cyst cavate; endocyst ovoidal to ellipsoidal with apical boss; pericyst discoidal, meridionally placed, with endophragm and periphragm in contact midventrally; wall surface smooth or nearly smooth with well-developed parasutural ridges; paratabulation gonyaulacacean, 4', 6'', 4-6c, 5-6''', 1p, 1'''', ?5-3s; archeopyle precingular, type P, 3'' only; distribution of paraplates such that nearly all of the dorsal area of the periphragm represents 3'' and is missing (see fig. 6) and the dorsal part of the paracingulum is displaced to form the antapical margin of the pericyst; up to five small paraplates may be distinguished in the parasulcal region; of holotype, pericyst length 90 µm, pericyst width 92 µm, endocyst length 54 µm, endocyst width 37 µm.
Description (annotated): Paratabulation well expressed where periphragm extends out from endophragm, well to poorly expressed midventrally (with younger specimens showing less definition in the midventral area than older specimens); paratabulation asymmetrical such that all of the pericyst tabulation is expressed on the ventral surface and what would be the dorsal side is missing; paracingulum displaced antapically so that what would normally be in the middorsal portion lies along the antapical margin and the paracingulum forms a characteristic eccentric circle on the ventral hypocyst; archeopyle precingular, type P, 3'' only in endocyst, presumably the missing dorsal side of the pericyst also represents 3''.
Dimensions: outer diameter, average 89 µm, range 63-113 µm; endocyst length, average 46 µm, range 37-58 µm; endocyst width, average 37 µm, range 31-60 µm; 25 specimens measured.
Affinities:
Edwards, 1984, p. 585-586
The discoidal shape, the prominent paratabulation, and the eccentric circle formed by the paracingulum distinguish this species from I. lacrymosa. This species only superficially resembles Thalassiphora delicata Williams and Downie, 1966, as emended by Eaton 1976 (contrast Fig. 6 with Eaton's text-figs. 18-20). In T. delicata, the wall layers are appressed middorsally and the large ventral opening represents paraplate 1''; in I. tabulata the wall layers are appressed midventrally, the large opening represents 3'', and the paracingulum is displaced antapically.
Holotype: Edwards, 1984, pl.3, figs.3A-B; text-figs.6A-B; Fensome et al., 1995, figs.1-4 - p.1837.
Stratum typicum: Middle-Late Miocene
Locus typicus: DSDP Site 555, E North Atlantic
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Invertocysta tabulata Edwards, 1984. Cyst cavate, endocyst with apical boss, periphragm and endophragm in contact ventrally. Well developed parasutural ridges, with paratabulation: 4', 6", 4-6c, 5-6"’, 1p, 1"”, ?3-5s. Nearly all of the dorsal area of the periphragm represents 3" and is missing. Size: Overall 63-113 µm, endocyst 37-58 µm long.
--------------------------------------------------
Original description: Edwards, 1984, p. 585
Diagnosis: Cyst cavate; endocyst ovoidal to ellipsoidal with apical boss; pericyst discoidal, meridionally placed, with endophragm and periphragm in contact midventrally; wall surface smooth or nearly smooth with well-developed parasutural ridges; paratabulation gonyaulacacean, 4', 6'', 4-6c, 5-6''', 1p, 1'''', ?5-3s; archeopyle precingular, type P, 3'' only; distribution of paraplates such that nearly all of the dorsal area of the periphragm represents 3'' and is missing (see fig. 6) and the dorsal part of the paracingulum is displaced to form the antapical margin of the pericyst; up to five small paraplates may be distinguished in the parasulcal region; of holotype, pericyst length 90 µm, pericyst width 92 µm, endocyst length 54 µm, endocyst width 37 µm.
Description (annotated): Paratabulation well expressed where periphragm extends out from endophragm, well to poorly expressed midventrally (with younger specimens showing less definition in the midventral area than older specimens); paratabulation asymmetrical such that all of the pericyst tabulation is expressed on the ventral surface and what would be the dorsal side is missing; paracingulum displaced antapically so that what would normally be in the middorsal portion lies along the antapical margin and the paracingulum forms a characteristic eccentric circle on the ventral hypocyst; archeopyle precingular, type P, 3'' only in endocyst, presumably the missing dorsal side of the pericyst also represents 3''.
Dimensions: outer diameter, average 89 µm, range 63-113 µm; endocyst length, average 46 µm, range 37-58 µm; endocyst width, average 37 µm, range 31-60 µm; 25 specimens measured.
Affinities:
Edwards, 1984, p. 585-586
The discoidal shape, the prominent paratabulation, and the eccentric circle formed by the paracingulum distinguish this species from I. lacrymosa. This species only superficially resembles Thalassiphora delicata Williams and Downie, 1966, as emended by Eaton 1976 (contrast Fig. 6 with Eaton's text-figs. 18-20). In T. delicata, the wall layers are appressed middorsally and the large ventral opening represents paraplate 1''; in I. tabulata the wall layers are appressed midventrally, the large opening represents 3'', and the paracingulum is displaced antapically.