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Lagenadinium callovianum
Lagenadinium callovianum Piel, 1985
NOW Stephanelytron. Originally Lagenadinium, subsequently (and now) Stephanelytron.
Holotype: Piel, 1985, pl.1, figs.1-6; Fensome et al., 1993a, figs.1-3 - p.1011.
Locus typicus: Warboys Borehole, Cambridgeshire, England
Stratum typicum: Middle to Late Callovian
Original description: Piel, 1985, p.108, 110, 112
Cysts subspherical to mostly ovoidal, proximochorate, holocavate. Body composed of two layers (autophragm and ectophragm) clearly separated by smooth, non-tabular, tubiform processes which are 2.0-4.0 µm long and 0.51.0 µm wide ([Piel, 1985] Plate III, 2). The processes are hollow, narrowest at their midpoint, and have their distal ends expanded more than the proximal. The autophragm is 0.5 µm or less in thickness. The ectophragm is 0.2-0.3 µm thick, commonly wrinkled, and is shown by electron microscopy to be microperforate ([Piel, 1985] Plate III, 3). An apical horn is present on both the autophragrn and ectophragm. The horn on the autophragm varies from a nipple-like form ([Piel, 1985] Plate I, 9), through successively broader and less elongate forms ([Piel, 1985] Plate I, 1-6 holotype; Plate I, 7), to a dome-like form ([Piel, 1985] Plate I, 8). The series is also shown in the composite line drawings of [Piel 1985] Fig.1. There is less variation in the horn on the ectophragm, the usual form being that shown on the holotype and on the specimen figured in [Piel, 1985] Plate I, 8.
Paratabulation is almost always limited to the occasional suggestion of a paracingulum or parasulcus ([Piel, 1985] Plate II, 7; Plate III, 1), the trace of the developing archeopyle sutures ([Piel, 1985] Plate I, 1, 3, 4, Plate II, 8Plate III, 1), and the angularity and accessory archeopyle sutures exhibited by the anterior portion of the precingular paraplates when the operculum is detached ([Piel, 1985] Plate II, 4-6 and Fig.2). Even so, it is clear that an apical archeopyle is present and that the operculum normally remains attached; there appear to be 5 precingular paraplates. The presence of many processes on the operculum also suggests that the operculum may be composed of several paraplates, in the same manner that the occurrence of one large process near the apex of Stephanelytron led Stover et al. (1977) to suggest a single apical paraplate in that genus.
Two coronas are present, and appear to be located either on paraplates in the postcingular series, or perhaps on the posterior intercalary and adjacent postcingular paraplate. The regular location of the two coronas (wherein one of them is located more antapically and closer to the probable parasulcus, and the other is more distant from both the antapex and the presumed parasulcus) suggests the latter arrangement, presuming that those paraplates have the same positional relationship shown by Stover et al. (1977) for similar paraplates in Stephanelytron tabulophorum. Additional evidence for this placement is taken from the specimen illustrated by line drawing in [Piel, 1985] Fig.la, in which the traces of the accessory archeopyle sutures appear to indicate the presence of a sulcal tongue in a position consistent with a posterior intercalary location for one of the coronas. If so, then the second corona seems to be located on the adjacent postcingular paraplate (? 1""" sensu Stover et al., 1977).The relationship of the two coronas to each other varies slightly, however - sometimes in contact, sometimes distinctly separated - apparently indicating that their position within the individual paraplates may not be as uniform as their general location ([Piel, 1985] Fig.2; Plate II, 2, 3).
There is no obvious size difference between the coronas on a particular specimen, but their shape varies from circular to oval with a sometimes irregular outline ([Piel, 1985] Figs.1, 2; Plate II, 2, 4; Plate III, 5).
Size ranges are as follows, taken from the measurements of 27 specimens (averages in parentheses): length (including operculum) = 33.6(43.5)-51.2 µm; width = 24.8-(34.4)-41.6 µm; coronas = 5.6-(8.6)-11.6 µm in plan view, and about 4.0 µm high in optical cross-section ([Piel, 1985] Plate II, 1).
NOW Stephanelytron. Originally Lagenadinium, subsequently (and now) Stephanelytron.
Holotype: Piel, 1985, pl.1, figs.1-6; Fensome et al., 1993a, figs.1-3 - p.1011.
Locus typicus: Warboys Borehole, Cambridgeshire, England
Stratum typicum: Middle to Late Callovian
Original description: Piel, 1985, p.108, 110, 112
Cysts subspherical to mostly ovoidal, proximochorate, holocavate. Body composed of two layers (autophragm and ectophragm) clearly separated by smooth, non-tabular, tubiform processes which are 2.0-4.0 µm long and 0.51.0 µm wide ([Piel, 1985] Plate III, 2). The processes are hollow, narrowest at their midpoint, and have their distal ends expanded more than the proximal. The autophragm is 0.5 µm or less in thickness. The ectophragm is 0.2-0.3 µm thick, commonly wrinkled, and is shown by electron microscopy to be microperforate ([Piel, 1985] Plate III, 3). An apical horn is present on both the autophragrn and ectophragm. The horn on the autophragm varies from a nipple-like form ([Piel, 1985] Plate I, 9), through successively broader and less elongate forms ([Piel, 1985] Plate I, 1-6 holotype; Plate I, 7), to a dome-like form ([Piel, 1985] Plate I, 8). The series is also shown in the composite line drawings of [Piel 1985] Fig.1. There is less variation in the horn on the ectophragm, the usual form being that shown on the holotype and on the specimen figured in [Piel, 1985] Plate I, 8.
Paratabulation is almost always limited to the occasional suggestion of a paracingulum or parasulcus ([Piel, 1985] Plate II, 7; Plate III, 1), the trace of the developing archeopyle sutures ([Piel, 1985] Plate I, 1, 3, 4, Plate II, 8Plate III, 1), and the angularity and accessory archeopyle sutures exhibited by the anterior portion of the precingular paraplates when the operculum is detached ([Piel, 1985] Plate II, 4-6 and Fig.2). Even so, it is clear that an apical archeopyle is present and that the operculum normally remains attached; there appear to be 5 precingular paraplates. The presence of many processes on the operculum also suggests that the operculum may be composed of several paraplates, in the same manner that the occurrence of one large process near the apex of Stephanelytron led Stover et al. (1977) to suggest a single apical paraplate in that genus.
Two coronas are present, and appear to be located either on paraplates in the postcingular series, or perhaps on the posterior intercalary and adjacent postcingular paraplate. The regular location of the two coronas (wherein one of them is located more antapically and closer to the probable parasulcus, and the other is more distant from both the antapex and the presumed parasulcus) suggests the latter arrangement, presuming that those paraplates have the same positional relationship shown by Stover et al. (1977) for similar paraplates in Stephanelytron tabulophorum. Additional evidence for this placement is taken from the specimen illustrated by line drawing in [Piel, 1985] Fig.la, in which the traces of the accessory archeopyle sutures appear to indicate the presence of a sulcal tongue in a position consistent with a posterior intercalary location for one of the coronas. If so, then the second corona seems to be located on the adjacent postcingular paraplate (? 1""" sensu Stover et al., 1977).The relationship of the two coronas to each other varies slightly, however - sometimes in contact, sometimes distinctly separated - apparently indicating that their position within the individual paraplates may not be as uniform as their general location ([Piel, 1985] Fig.2; Plate II, 2, 3).
There is no obvious size difference between the coronas on a particular specimen, but their shape varies from circular to oval with a sometimes irregular outline ([Piel, 1985] Figs.1, 2; Plate II, 2, 4; Plate III, 5).
Size ranges are as follows, taken from the measurements of 27 specimens (averages in parentheses): length (including operculum) = 33.6(43.5)-51.2 µm; width = 24.8-(34.4)-41.6 µm; coronas = 5.6-(8.6)-11.6 µm in plan view, and about 4.0 µm high in optical cross-section ([Piel, 1985] Plate II, 1).