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Evittosphaerula paratabulata
Evittosphaerula paratabulata Manum, 1979, p.243,246, pl.2, figs.1–12; text-figs.3–4. Emendation: Damassa, 1997, p.166.
Holotype: Manum, 1979, pl.2, figs.6-10
Age: Middle Oligocene-Early Miocene
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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.
Evittosphaerula paratabulata Manum, 1979, emend. Damassa, 1997. According to Manum (1979, p.243), Evittosphaerula paratabulata is spherical to subspherical, with only the parasutural network preserved. Parasutures are T shaped in cross-section. There are four apical plates symmetrically arranged around a small preapical, six precingulars, with the 6" not touching the apicals and the 5" touching the large as, six cingulars, six postcingulars, one posterior intercalary and one antapical. In the sulcus are two distinct pairs of small plates below the anterior sulcal, in addition to the usual right, left and posterior sulcal plates. Size: range 70-105 µm.
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Original description: Manum, 1979, p. 243
Dinoflagellate cysts of spherical to subspherical shape, consisting of a parasutural network as the only fossilizeable wall structure. Parasutures T-shaped in cross-section, composed of a ribbon-like, apparently structureless base ca. 3 Ám wide and a median septum 4--5 Ám high, which appears fibrous in the light microscope and has a finely sinuous crest giving it a beaded appearance in top view.
The epicyst has four apical paraplates symmetrically arranged around a small preapical paraplate.
Then follows, in apical view, a series of six paraplates of rather equal size, of which the one occupying the mid-ventral position is interpreted as the anterior sulcal. The sixth precingular paraplate is rather small and not in touch with the apical series. Paracingulum shows six rather broad paraplates. In the hypocyst there are six postcingular paraplates, one posterior intercalary and one antapical paraplate. The sulcal zone shows two distinct pairs of small paraplates below the anterior sulcal, in addition to the usual right, left, and posterior sulcals.
Dimensions: Maximum diameter of holotype 98 Ám, of paratype 104 Ám; ranging between 70 Ám and 105 Ám depending on amount of compression and distortion.
Affinities: Manum, 1979, p. 243, 246
All that persists of this cyst in the fossil state is a parasutural network. The wall of the living cyst is considered to have been composed of perishable substances for the greater part; only in narrow bands along the parasutures was the resistant material deposited during cyst formation. The differentiation of the parasutural bands into a structureless base and a fibrous septum suggest a double nature of the wall, but it is doubtful whether the endophragm--periphragm concept is applicable since they are not discernible as separate structures. As an obvious consequence of the network construction of the cys an archeopyle cannot be identified. The paratabulation is unique in its over-all appearance. Usually, cysts possessing a well-defined paracingulum are not difficult to orient, but in this form confusion is caused by the width of the cingular paraplates which makes them look little different from many of the other paraplates. Other striking features are the strong bilateral symmetry of the paratabulation viewed from the apex and the cluster of small paraplates in the sulcal zone (cf. Fig.3). Although the paratabulation is expressed exceptionally well, its interpretation is not altogether unproblematic. The large mid-ventral paraplate in the epicyst, here interpreted as anterior sulcal, presents a key point in the problem The interpretation proposed in Fig.3 results in a number of apical paraplates and relationships between apical and precingular paraplates which are consistent with known gonyaulacacean tabulations. The main difference from typical Gonyaulax tabulation is in the exceptionally large as. Remaining sulcal paratabulation is consistent with typical Gonyaulax, however with an extra pair of accessory sulcal paraplates adjacent to as (pre-right and pre-left accessory sulcals respectively, Fig.3C). The alternative interpretation which appears most reasonable is to consider the mid-ventral paraplate as the first apical and not anterior sulcal. Following this, plas in Fig.3C will change to as, and pras to the last of the precingular series (7"). This interpretation, however, would lead to an unusual epicyst paratabulation formula lacking known homologues. Therefore, a formula which implies a gonyaulacacean homology is preferred, particularly when it may be applied without serious constraints. There is a certain amount of resemblance with the tabulation in the extant species Gonyaulax balechii Steidinger (1971). This species, too, possesses supernumerary sulcal plates, a fairly large mid-ventral plate above the small sulcals, and a reduced sixth precingular. On closer comparison, however, significant differences become apparent which exclude close affinity (f.i. in the configuration of plates in the apical series and of the 6"', ps and 1"").
The unusual width and shape of the cingular paraplates in E. paratabulata as noted above, and also the extraordinary size of the anterior sulcal paraplate, may serve to emphasize that size and shape of plates reflected in the cyst wall will often appear distorted in comparison with their thecal counterparts. However, their polygonality, which results from the number of adjacent plates, remains unchanged from theca to cyst.
Holotype: Manum, 1979, pl.2, figs.6-10
Age: Middle Oligocene-Early Miocene
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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.
Evittosphaerula paratabulata Manum, 1979, emend. Damassa, 1997. According to Manum (1979, p.243), Evittosphaerula paratabulata is spherical to subspherical, with only the parasutural network preserved. Parasutures are T shaped in cross-section. There are four apical plates symmetrically arranged around a small preapical, six precingulars, with the 6" not touching the apicals and the 5" touching the large as, six cingulars, six postcingulars, one posterior intercalary and one antapical. In the sulcus are two distinct pairs of small plates below the anterior sulcal, in addition to the usual right, left and posterior sulcal plates. Size: range 70-105 µm.
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Original description: Manum, 1979, p. 243
Dinoflagellate cysts of spherical to subspherical shape, consisting of a parasutural network as the only fossilizeable wall structure. Parasutures T-shaped in cross-section, composed of a ribbon-like, apparently structureless base ca. 3 Ám wide and a median septum 4--5 Ám high, which appears fibrous in the light microscope and has a finely sinuous crest giving it a beaded appearance in top view.
The epicyst has four apical paraplates symmetrically arranged around a small preapical paraplate.
Then follows, in apical view, a series of six paraplates of rather equal size, of which the one occupying the mid-ventral position is interpreted as the anterior sulcal. The sixth precingular paraplate is rather small and not in touch with the apical series. Paracingulum shows six rather broad paraplates. In the hypocyst there are six postcingular paraplates, one posterior intercalary and one antapical paraplate. The sulcal zone shows two distinct pairs of small paraplates below the anterior sulcal, in addition to the usual right, left, and posterior sulcals.
Dimensions: Maximum diameter of holotype 98 Ám, of paratype 104 Ám; ranging between 70 Ám and 105 Ám depending on amount of compression and distortion.
Affinities: Manum, 1979, p. 243, 246
All that persists of this cyst in the fossil state is a parasutural network. The wall of the living cyst is considered to have been composed of perishable substances for the greater part; only in narrow bands along the parasutures was the resistant material deposited during cyst formation. The differentiation of the parasutural bands into a structureless base and a fibrous septum suggest a double nature of the wall, but it is doubtful whether the endophragm--periphragm concept is applicable since they are not discernible as separate structures. As an obvious consequence of the network construction of the cys an archeopyle cannot be identified. The paratabulation is unique in its over-all appearance. Usually, cysts possessing a well-defined paracingulum are not difficult to orient, but in this form confusion is caused by the width of the cingular paraplates which makes them look little different from many of the other paraplates. Other striking features are the strong bilateral symmetry of the paratabulation viewed from the apex and the cluster of small paraplates in the sulcal zone (cf. Fig.3). Although the paratabulation is expressed exceptionally well, its interpretation is not altogether unproblematic. The large mid-ventral paraplate in the epicyst, here interpreted as anterior sulcal, presents a key point in the problem The interpretation proposed in Fig.3 results in a number of apical paraplates and relationships between apical and precingular paraplates which are consistent with known gonyaulacacean tabulations. The main difference from typical Gonyaulax tabulation is in the exceptionally large as. Remaining sulcal paratabulation is consistent with typical Gonyaulax, however with an extra pair of accessory sulcal paraplates adjacent to as (pre-right and pre-left accessory sulcals respectively, Fig.3C). The alternative interpretation which appears most reasonable is to consider the mid-ventral paraplate as the first apical and not anterior sulcal. Following this, plas in Fig.3C will change to as, and pras to the last of the precingular series (7"). This interpretation, however, would lead to an unusual epicyst paratabulation formula lacking known homologues. Therefore, a formula which implies a gonyaulacacean homology is preferred, particularly when it may be applied without serious constraints. There is a certain amount of resemblance with the tabulation in the extant species Gonyaulax balechii Steidinger (1971). This species, too, possesses supernumerary sulcal plates, a fairly large mid-ventral plate above the small sulcals, and a reduced sixth precingular. On closer comparison, however, significant differences become apparent which exclude close affinity (f.i. in the configuration of plates in the apical series and of the 6"', ps and 1"").
The unusual width and shape of the cingular paraplates in E. paratabulata as noted above, and also the extraordinary size of the anterior sulcal paraplate, may serve to emphasize that size and shape of plates reflected in the cyst wall will often appear distorted in comparison with their thecal counterparts. However, their polygonality, which results from the number of adjacent plates, remains unchanged from theca to cyst.