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Ectosphaeridium picenum
Ectosphaeridium picenum (Biffi and Manum, 1988, p.190,192, pl.7, figs.1-3,5-7,9,12) Zevenboom and Santarelli in Zevenboom, 1995, p.150. Emendation: Zevenboom and Santarelli in Zevenboom, 1995, p.151, as Ectosphaeridium picenum.
Combination not validly published: generic name not validly published.
NOW Membranilarnacia?. Originally (and now) Membranilarnacia, subsequently Ectosphaeridium (combination not validly published).
Holotype: Biffi and Manum, 1988, pl.7, figs.1,5,9,12; Fauconnier and Masure, 2004, pl.54, figs.12-13.
Age: Early Miocene.
Original description: Biffi and Manum, 1988, p. 190-192
Diagnosis: Holocavate cyst of subsphaerical shape; archeopyle apical (tA), operculum simple. Sulcal notch short and narrow. Autophragm spongy to pitted externally, seemingly unstructured internally. Very numerous processes arranged in poorly defined intratabular clusters, expanding distally to produce a veil-like ectophragm with some indications of parasutures, particularly along the archeopyle. Process bases of buttressing fibres, main stem non-fibrous.
Dimensions: Holotype: cyst breadth 49 µm; cyst length without processes 40 µm; periphragm ectophragm separation 8 Ám. Mean values (bracketed) and extremes (n = 20): cyst breadth 46(52)57 µm; cyst length 37(43)50 µm; periphragm ectophragm separation 5-8 µm.
Description (annotated): ...perforations, a few microns wide, occur it the ectophragm. In favourably preserved and oriented specimens an intratabular arrangement of the process clusters and parasutural interruptions are discernible, particularly along the archeopyle suture, where the ectophragm shows deep U-shaped parasutural notches and sometimes even complete paraplate separations coinciding with parasutural notches in the cyst wall proper. Six large and one small process clusters are discernible along the archeopyle suture, reflecting the 6 precingulars plus anterior sulcal plate. It has not been possible to make out the complete paratabulation using only the light microscope because of the confusing image produced by the very numerous processes. The sulcal notch seems to be off-set to the left; however it is difficult to be sure about this, since tendency towards dorsoventral orientation is particularly strong. The sulcal notch is short and shallow and 6'' has an asymmetric geniculate top with the shorter edge on the left side; 1'' and 5'' are both about half time wider than 6''. There are no processes features to indicate the cingulum.
Remarks: This distinctive cyst is easy to recognize but not easy to interpret morphologically, even if the orientation is favourable; SEM studies are necessary for a proper understanding. It does not compare well with any known species of Glaphyrocysta (Stover and Evitt, 1978) with its relatively short processes showing no reduction in size or density in dorsal and ventral areas. It seems more related to the genus Membranilarnacia Eisenack (1963) emend. Williams and Downie (1966), the main difference being the processes that are 'evidently not paraplate related' (Stover and Evitt, 1978, p. 63). At present we prefer to make provisional reference to Membranilarnacia Eisenack (1963) rather than to erect a new genus.
Combination not validly published: generic name not validly published.
NOW Membranilarnacia?. Originally (and now) Membranilarnacia, subsequently Ectosphaeridium (combination not validly published).
Holotype: Biffi and Manum, 1988, pl.7, figs.1,5,9,12; Fauconnier and Masure, 2004, pl.54, figs.12-13.
Age: Early Miocene.
Original description: Biffi and Manum, 1988, p. 190-192
Diagnosis: Holocavate cyst of subsphaerical shape; archeopyle apical (tA), operculum simple. Sulcal notch short and narrow. Autophragm spongy to pitted externally, seemingly unstructured internally. Very numerous processes arranged in poorly defined intratabular clusters, expanding distally to produce a veil-like ectophragm with some indications of parasutures, particularly along the archeopyle. Process bases of buttressing fibres, main stem non-fibrous.
Dimensions: Holotype: cyst breadth 49 µm; cyst length without processes 40 µm; periphragm ectophragm separation 8 Ám. Mean values (bracketed) and extremes (n = 20): cyst breadth 46(52)57 µm; cyst length 37(43)50 µm; periphragm ectophragm separation 5-8 µm.
Description (annotated): ...perforations, a few microns wide, occur it the ectophragm. In favourably preserved and oriented specimens an intratabular arrangement of the process clusters and parasutural interruptions are discernible, particularly along the archeopyle suture, where the ectophragm shows deep U-shaped parasutural notches and sometimes even complete paraplate separations coinciding with parasutural notches in the cyst wall proper. Six large and one small process clusters are discernible along the archeopyle suture, reflecting the 6 precingulars plus anterior sulcal plate. It has not been possible to make out the complete paratabulation using only the light microscope because of the confusing image produced by the very numerous processes. The sulcal notch seems to be off-set to the left; however it is difficult to be sure about this, since tendency towards dorsoventral orientation is particularly strong. The sulcal notch is short and shallow and 6'' has an asymmetric geniculate top with the shorter edge on the left side; 1'' and 5'' are both about half time wider than 6''. There are no processes features to indicate the cingulum.
Remarks: This distinctive cyst is easy to recognize but not easy to interpret morphologically, even if the orientation is favourable; SEM studies are necessary for a proper understanding. It does not compare well with any known species of Glaphyrocysta (Stover and Evitt, 1978) with its relatively short processes showing no reduction in size or density in dorsal and ventral areas. It seems more related to the genus Membranilarnacia Eisenack (1963) emend. Williams and Downie (1966), the main difference being the processes that are 'evidently not paraplate related' (Stover and Evitt, 1978, p. 63). At present we prefer to make provisional reference to Membranilarnacia Eisenack (1963) rather than to erect a new genus.