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Apteodinium palliatum
Apteodinium palliatum, Stevens, 1987
Holotype: Stevens, 1987, fig.3A-B
Locus typicus: Exmouth Plateau, Australia
Stratum typicum: Early Berriasian
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Original description: [Stevens, 1987, p. 185-186]:
Description:
Cysts proximate and subspherical with a rounded reticulate apical horn 7(12)18 µm in length, 2-layered, with a smooth 2-3 µm thick endophragm and a reticulate periphragm, varying in thickness from 1-4 µm (being thicker at the apices and equator). Reticulum of broad, rounded muri (up to 2 µm high and 2-3 µm wide), delineating irregular to subcircular lumina, 1(3)5 µm in diameter. Where reticulum thin and incomplete discontinuous muri form irregular verrucae (2-4 µm in diameter) (Fig.3F) randomly scattered 3-8 µm apart.
Archeopyle precingular, type P (3" only), extending from the paracingulum to close to the apical horn, being 28(36)46 µm long with the length greater than the width. Operculum free and generally absent.
Paratabulation indicated by the archeopyle paracingulum and parasulcus only.
Paracingulum expressed by an equatorial thickening of the periphragm, appearing offset.
Parasulcus indicated by a deep, smooth to perforate groove or broad depression (22(31)46 µm long) on the hypocyst, extending posteriorly from the paracingulum one half to two thirds the length of the hypocyst, and with a flagellar scar (4-6 µm long) commonly present at its anterior end.
Variability:
The cysts are consistently large and subspherical. The reticulate periphragm varies in thickness, being thickest at the apices and equator (Fig.3A,E-G), and is generally thin elsewhere. Where thin, the reticulum may be incomplete, forming verrucae (Fig.3F) where muri are discontinuous. The precingular archeopyle is always large and its length is greater than its width (Fig.3B); due to its consistent location opposite the parasulcus it is interpreted as being the 3" paraplate. The operculum may be in place. The paracingulum is expressed by a reticulate, equatorial band of thickened periphragm (Fig.3E,G). The parasulcus may be indicated by either a deep groove (Fig.3A) or a broad depression (Fig.3E,G) and a flagellar scar is commonly present (Fig.3C,D).
Dimensions:
Cyst length 86(110)140 µm, cyst width 72(93)132 µm (28 specimens).
Affinities:
Apteodinium palliatum, A. reticulatum Singh 1971 and A. maculatum Eisenack & Cookson 1960 are all reticulate. However, A. reticulatum is smaller with smaller lumina and a smooth, hollow apical horn and A. maculatum has lumina confined to the intratabular areas only. Apteodinium palliatum differs from other species of Apteodinium in being reticulate.
Holotype: Stevens, 1987, fig.3A-B
Locus typicus: Exmouth Plateau, Australia
Stratum typicum: Early Berriasian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Stevens, 1987, p. 185-186]:
Description:
Cysts proximate and subspherical with a rounded reticulate apical horn 7(12)18 µm in length, 2-layered, with a smooth 2-3 µm thick endophragm and a reticulate periphragm, varying in thickness from 1-4 µm (being thicker at the apices and equator). Reticulum of broad, rounded muri (up to 2 µm high and 2-3 µm wide), delineating irregular to subcircular lumina, 1(3)5 µm in diameter. Where reticulum thin and incomplete discontinuous muri form irregular verrucae (2-4 µm in diameter) (Fig.3F) randomly scattered 3-8 µm apart.
Archeopyle precingular, type P (3" only), extending from the paracingulum to close to the apical horn, being 28(36)46 µm long with the length greater than the width. Operculum free and generally absent.
Paratabulation indicated by the archeopyle paracingulum and parasulcus only.
Paracingulum expressed by an equatorial thickening of the periphragm, appearing offset.
Parasulcus indicated by a deep, smooth to perforate groove or broad depression (22(31)46 µm long) on the hypocyst, extending posteriorly from the paracingulum one half to two thirds the length of the hypocyst, and with a flagellar scar (4-6 µm long) commonly present at its anterior end.
Variability:
The cysts are consistently large and subspherical. The reticulate periphragm varies in thickness, being thickest at the apices and equator (Fig.3A,E-G), and is generally thin elsewhere. Where thin, the reticulum may be incomplete, forming verrucae (Fig.3F) where muri are discontinuous. The precingular archeopyle is always large and its length is greater than its width (Fig.3B); due to its consistent location opposite the parasulcus it is interpreted as being the 3" paraplate. The operculum may be in place. The paracingulum is expressed by a reticulate, equatorial band of thickened periphragm (Fig.3E,G). The parasulcus may be indicated by either a deep groove (Fig.3A) or a broad depression (Fig.3E,G) and a flagellar scar is commonly present (Fig.3C,D).
Dimensions:
Cyst length 86(110)140 µm, cyst width 72(93)132 µm (28 specimens).
Affinities:
Apteodinium palliatum, A. reticulatum Singh 1971 and A. maculatum Eisenack & Cookson 1960 are all reticulate. However, A. reticulatum is smaller with smaller lumina and a smooth, hollow apical horn and A. maculatum has lumina confined to the intratabular areas only. Apteodinium palliatum differs from other species of Apteodinium in being reticulate.