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Epitricysta vinckensis
Epitricysta vinckensis Stover and Helby, 1987
Holotype: Stover and Helby, 1987, fig.9E-G,M-N
Locus typicus: Exmouth Plateau, W Australia
Stratum typicum: Hauterivian-Aptian
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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.
Epitricysta vinckensis Stover and Helby, 1987c, has preferred apical antapical orientation, irregularly pitted autophragm bearing parasutural ridges or septa. Parasutural features are 2-3 µm in height, with smooth or occasionally spinate crests. A single transverse, distally entire to spinate flange, with slightly offset ends, denotes the paracingulum. The cingular flange may be smooth, faintly ornamented, or with scattered perforations or fenestrate locally. Size: cyst body 57-86 µm, dorsal-ventral 58-84 µm.
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Original description: Stover and Helby, 1987, p. 234-235, 238
Cysts proximate, oblately spherical to ellipsoidal, with a preferred apical-antapical orientation. On specimens with elliptical rather than subcircular outline in apical-antapical view the transverse dimension usually greater than the dorsal-ventral dimension. Autophragm about 2.5 Ám thick, irregularly pitted (Figs. 8H,I, 9E,M) or grooved (occasionally deeply so), bearing continuous but more commonly incomplete parasutural ridges or septa which tend to be developed best in the nonpolar areas especially on the epicyst (Fig. 9A-C,E,F). Parasutural features typically narrow, 2-3 Ám or less in height with smooth or, much less commonly, spinate crests. Parasutural ridges indicate a paratabulation of 3' 7", Xc, 5''', 1p, 1'''', and 1 or more s arrangement of the epicystal paraplates very similar to that of epithecal plates on Triadinium (cf. Fig.7A,C). A single, transverse, distally even to spinate flange (Figs 8H,L, 9L,N), with slightly offset ends, denoting the paracingulum. Cingular flange smooth to faintly ornamented, or with scattered perforations, or fenestrate locally. From 2.5-8 Ám wide, of nearly uniform width, or may be narrow dorsally and gradually increase in width ventrally. Spines 2-6.5 Ám long, 1.5-3 Ám wide, usually longer than wide. Spine tips simple, bifurcate, or trifurcate. Interruption of the cingular flange and an indentation in the midventral area interpreted as indicating the position of the parasulcus. In the midventral area at about the plane of the cingular flange, (i.e. within the parasulcus) two, short, bluntly rounded projections, marginal (at least laterally) to a porelike depression (Figs 8K, 9F-I,M). Principal suture of the [tAtPla archeopyle anterior to, parallel to, and very near the cingular flange. No specimen found with the suture closed upon itself. Exclusive of the flange, transverse dimension of the cyst body 57-86 Ám, and its dorsal ventral dimension 58-84Ám; 20 specimens measured.
Paratabulation. On E. vinckensis (Fig.7A,B), the apical series consists of 3, moderately sized, 5-sided paraplates whose common junction occurs near the apex. There is no evidence of a preapical paraplate. The precingular series is composed of 7 paraplates; 3'', 5'' and 7'' are flat-topped anteriorly, whereas 2'', 4'' and 6'' are gabled. Paraplate 1'' is subquadrangular, narrow, longitudinally elongate, and usually more poorly delimited than the others. Paraplates 2'' to 5'' are fairly similar in width, wider than 7'', and not as wide as 6'', which is the widest of the precingulars. The similarity of epicystal paratabulation of E. vinckensis to the epithecal tabulation of Triadinium polyedricum can be seen by comparing Fig.7A with Fig.7C. However, there are noteworthy differences. For instance, a preapical paraplate (equivalent to the Po thecal plate) is missing on E. vinckensis. On T. polyedricum, the first apical contacts the second precingular, whereas on E. vinckensis the first apical fails to contact the second precingular (owing to the intervention of 1'' ) and contacts the second apical paraplate.
We interpret the hypocyst of E. vinckensis as consisting of 7 paraplates, not including those in the parasulcus (Fig.7B). The dominant feature of the hypocyst is the exceptionally large antapical paraplate, which has 4 relatively long sides and a fifth, short, ventral side. We are uncertain whether this side is composed of 1 or 2 segments. Of the 5 postcingular paraplates, 4 (2''' to 5''' ) are large and trapezoidal, while the fifth (1''') is small. Separation of it from the quadrangular 1p is not always evident. A quadrangular posterior sulcal paraplate occurs in the midventral area; the shape of this paraplate is frequently distorted and appears triangular or crescent shaped, as well as quadrate. The hypocystal paratabulation on E. vinckensis is apparently unique and is distinctly unlike the hypothecal tabulation on T. polyedricum (Fig.7D).
Holotype: Stover and Helby, 1987, fig.9E-G,M-N
Locus typicus: Exmouth Plateau, W Australia
Stratum typicum: Hauterivian-Aptian
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Epitricysta vinckensis Stover and Helby, 1987c, has preferred apical antapical orientation, irregularly pitted autophragm bearing parasutural ridges or septa. Parasutural features are 2-3 µm in height, with smooth or occasionally spinate crests. A single transverse, distally entire to spinate flange, with slightly offset ends, denotes the paracingulum. The cingular flange may be smooth, faintly ornamented, or with scattered perforations or fenestrate locally. Size: cyst body 57-86 µm, dorsal-ventral 58-84 µm.
--------------------------------------------------
Original description: Stover and Helby, 1987, p. 234-235, 238
Cysts proximate, oblately spherical to ellipsoidal, with a preferred apical-antapical orientation. On specimens with elliptical rather than subcircular outline in apical-antapical view the transverse dimension usually greater than the dorsal-ventral dimension. Autophragm about 2.5 Ám thick, irregularly pitted (Figs. 8H,I, 9E,M) or grooved (occasionally deeply so), bearing continuous but more commonly incomplete parasutural ridges or septa which tend to be developed best in the nonpolar areas especially on the epicyst (Fig. 9A-C,E,F). Parasutural features typically narrow, 2-3 Ám or less in height with smooth or, much less commonly, spinate crests. Parasutural ridges indicate a paratabulation of 3' 7", Xc, 5''', 1p, 1'''', and 1 or more s arrangement of the epicystal paraplates very similar to that of epithecal plates on Triadinium (cf. Fig.7A,C). A single, transverse, distally even to spinate flange (Figs 8H,L, 9L,N), with slightly offset ends, denoting the paracingulum. Cingular flange smooth to faintly ornamented, or with scattered perforations, or fenestrate locally. From 2.5-8 Ám wide, of nearly uniform width, or may be narrow dorsally and gradually increase in width ventrally. Spines 2-6.5 Ám long, 1.5-3 Ám wide, usually longer than wide. Spine tips simple, bifurcate, or trifurcate. Interruption of the cingular flange and an indentation in the midventral area interpreted as indicating the position of the parasulcus. In the midventral area at about the plane of the cingular flange, (i.e. within the parasulcus) two, short, bluntly rounded projections, marginal (at least laterally) to a porelike depression (Figs 8K, 9F-I,M). Principal suture of the [tAtPla archeopyle anterior to, parallel to, and very near the cingular flange. No specimen found with the suture closed upon itself. Exclusive of the flange, transverse dimension of the cyst body 57-86 Ám, and its dorsal ventral dimension 58-84Ám; 20 specimens measured.
Paratabulation. On E. vinckensis (Fig.7A,B), the apical series consists of 3, moderately sized, 5-sided paraplates whose common junction occurs near the apex. There is no evidence of a preapical paraplate. The precingular series is composed of 7 paraplates; 3'', 5'' and 7'' are flat-topped anteriorly, whereas 2'', 4'' and 6'' are gabled. Paraplate 1'' is subquadrangular, narrow, longitudinally elongate, and usually more poorly delimited than the others. Paraplates 2'' to 5'' are fairly similar in width, wider than 7'', and not as wide as 6'', which is the widest of the precingulars. The similarity of epicystal paratabulation of E. vinckensis to the epithecal tabulation of Triadinium polyedricum can be seen by comparing Fig.7A with Fig.7C. However, there are noteworthy differences. For instance, a preapical paraplate (equivalent to the Po thecal plate) is missing on E. vinckensis. On T. polyedricum, the first apical contacts the second precingular, whereas on E. vinckensis the first apical fails to contact the second precingular (owing to the intervention of 1'' ) and contacts the second apical paraplate.
We interpret the hypocyst of E. vinckensis as consisting of 7 paraplates, not including those in the parasulcus (Fig.7B). The dominant feature of the hypocyst is the exceptionally large antapical paraplate, which has 4 relatively long sides and a fifth, short, ventral side. We are uncertain whether this side is composed of 1 or 2 segments. Of the 5 postcingular paraplates, 4 (2''' to 5''' ) are large and trapezoidal, while the fifth (1''') is small. Separation of it from the quadrangular 1p is not always evident. A quadrangular posterior sulcal paraplate occurs in the midventral area; the shape of this paraplate is frequently distorted and appears triangular or crescent shaped, as well as quadrate. The hypocystal paratabulation on E. vinckensis is apparently unique and is distinctly unlike the hypothecal tabulation on T. polyedricum (Fig.7D).