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Paralecaniella indentata
Paralecaniella indentata (Deflandre and Cookson, 1955) Cookson and Eisenack, 1970; emend. Elsik, 1977
Acritarch genus
Originally Epicephalopyxis, subsequently (and now) Paralecaniella.
Tax. sr. synonym of Scriniodinium nilsii Kjellstr÷m, 1973, according to Jan du Chene et al., 1986.
Holotype: Deflandre and Cookson, 1955, pl. 9, fig. 6
Locus typicus: Birregurra, Bore No. 1, Victoria, Australia
Stratum typicum: Paleocene- Miocene
Original description: Deflandre and Cookson, 1955, p. 292-293: Epicephalopyxis indentata.
Diagnosis: Organism more or less deeply cap- or dome-shaped, with a circular or elliptical outline provided with a relatively narrow, smooth, irregularly notched, slightly wavy rim. Surface membrane finely granular.
Dimensions: 51-74 by 43-69 Ám, extremes 51 by 51 Ám, 74 by 59 Ám.
Emended description: Elsik, 1977, p. 96-100.
Diagnosis as for the genus:
Separate layers extremely thin to ca. 1 Ám thick.
Remarks (annotated): Morphologic variations and criteria for recognition of Paralecaniella exhibited by specimens illustrated by specimens illustrated in Plate 1 and Plate 2 include:
1. A thin walled, generally psilate inner body which may split into near equal or unequal parts.
2. A psilate to ornamented outer wall of variable thickness, layering and continuity.
3. A flange of variable expression, both structurally and in rigidity.
4. The outer wall complex, apparently including the flange area, may also split into near equal or unequal parts.
5. Irregular invaginations of the outer wall apparently anchor the inner body. Invaginations on opposite sides a specimen may be joined by continual line, or at least continuous equatorial shadow band across the width of the specimen. Occasional specimens have paired invaginations suggestive of a flagellar sulcus or cingulum, depending upon interpretation of the orientation of the cysts.
6. Both the inner body and outer wall may be of unequal development in thickness and ornament between the two halves of a specimen.
7. A complete specimen has not been seen in edge view to establish the presence or absence of an equatorial cingulum or sulcus. Generally, half specimens either lacking invaginations or having two opposite invaginations are recovered. Unfortunately, entire specimens also may or may not have the invagination, thus it is not certain that the half lacking the invagination is apical and the half with it is antapical! The irregular notches, when more than two are developed (text-fig. 1A), are perhaps expressions of plate structure. The morphology of the cyst and possible orientation and direction of travel of the living organism are depicted by line drawing in text-fig. 1.
Affinities:
Elsik, 1977, p. 100: Paralecaniella indentata occurs in marginal marine to marine strata with dinoflagellates and acritarchs. The basic morphology, if interpreted as nearly equal parts of a whole, places the form in that broad group of schizosporous microfossils in which various expressions of wall layering and presence or absence of inner bodies may be found. Alternately, the equatorial sulcus/cingulum-like modification that may be present on one half of Paralecaniella indentata is not characteristic of that broad group of schizospores, whether algae or acritarchs.
Acritarch genus
Originally Epicephalopyxis, subsequently (and now) Paralecaniella.
Tax. sr. synonym of Scriniodinium nilsii Kjellstr÷m, 1973, according to Jan du Chene et al., 1986.
Holotype: Deflandre and Cookson, 1955, pl. 9, fig. 6
Locus typicus: Birregurra, Bore No. 1, Victoria, Australia
Stratum typicum: Paleocene- Miocene
Original description: Deflandre and Cookson, 1955, p. 292-293: Epicephalopyxis indentata.
Diagnosis: Organism more or less deeply cap- or dome-shaped, with a circular or elliptical outline provided with a relatively narrow, smooth, irregularly notched, slightly wavy rim. Surface membrane finely granular.
Dimensions: 51-74 by 43-69 Ám, extremes 51 by 51 Ám, 74 by 59 Ám.
Emended description: Elsik, 1977, p. 96-100.
Diagnosis as for the genus:
Separate layers extremely thin to ca. 1 Ám thick.
Remarks (annotated): Morphologic variations and criteria for recognition of Paralecaniella exhibited by specimens illustrated by specimens illustrated in Plate 1 and Plate 2 include:
1. A thin walled, generally psilate inner body which may split into near equal or unequal parts.
2. A psilate to ornamented outer wall of variable thickness, layering and continuity.
3. A flange of variable expression, both structurally and in rigidity.
4. The outer wall complex, apparently including the flange area, may also split into near equal or unequal parts.
5. Irregular invaginations of the outer wall apparently anchor the inner body. Invaginations on opposite sides a specimen may be joined by continual line, or at least continuous equatorial shadow band across the width of the specimen. Occasional specimens have paired invaginations suggestive of a flagellar sulcus or cingulum, depending upon interpretation of the orientation of the cysts.
6. Both the inner body and outer wall may be of unequal development in thickness and ornament between the two halves of a specimen.
7. A complete specimen has not been seen in edge view to establish the presence or absence of an equatorial cingulum or sulcus. Generally, half specimens either lacking invaginations or having two opposite invaginations are recovered. Unfortunately, entire specimens also may or may not have the invagination, thus it is not certain that the half lacking the invagination is apical and the half with it is antapical! The irregular notches, when more than two are developed (text-fig. 1A), are perhaps expressions of plate structure. The morphology of the cyst and possible orientation and direction of travel of the living organism are depicted by line drawing in text-fig. 1.
Affinities:
Elsik, 1977, p. 100: Paralecaniella indentata occurs in marginal marine to marine strata with dinoflagellates and acritarchs. The basic morphology, if interpreted as nearly equal parts of a whole, places the form in that broad group of schizosporous microfossils in which various expressions of wall layering and presence or absence of inner bodies may be found. Alternately, the equatorial sulcus/cingulum-like modification that may be present on one half of Paralecaniella indentata is not characteristic of that broad group of schizospores, whether algae or acritarchs.