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Pseudoceratium exquisitum
Pseudoceratium exquisitum (Morgan, 1980) Helby, 1987
Now Endoceratium. Originally (and now) Endoceratium, subsequently Pseudoceratium. Lentin and Williams, 1989 retained this species in Endoceratium Vozzhennikova, 1965.
Holotype: Morgan, 1980, pl.10, figs.11-12
Locus typicus: Wanaaring, New South Wales, Australia
Stratum typicum: Early-late Albian
Original description: Morgan, 1980, p. 22: Endoceratium exquisitum
Rounded triangular ambitus, two layered; apical horn, one lateral and one antapical horn strongly developed and distally rounded, second antapical and second lateral horn weakly developed; endophragm psilate, subtriangular; ectophragm subtriangular, with even bimodal perforations, 2-3 µm in diameter, and 0.5 µm in diameter wall layers in contact on dorsal and ventral surfaces, free elsewhere, resulting in an ambital pericoel 8-12 µm wide; nontabulate: archeopyle apical operculum free; accessory archeopyle sutures indicate six precingular plates and slightly notched sulcus indicating gonyaulacean tabulation.
Affinities:
Morgan, 1980, p. 22: Endoceratium exquisitum
E. exquisitum has a perforate ectophragm, while E. ludbrookii and E. dettmannii have a solid periphragm. E. dettmannii has large irregular dorsal and ventral areas of separation between the endophragm and periphragm. E ludbrookii either has the wall layers closely appressed, or with small areas of separation, often reflecting tabulation. Some specimens of Pseudoceratium turneri have a perforate ectophragm supported by numerous fibrous processes. This form probably develops into E. exquisitum by loss of the supporting processes.
Now Endoceratium. Originally (and now) Endoceratium, subsequently Pseudoceratium. Lentin and Williams, 1989 retained this species in Endoceratium Vozzhennikova, 1965.
Holotype: Morgan, 1980, pl.10, figs.11-12
Locus typicus: Wanaaring, New South Wales, Australia
Stratum typicum: Early-late Albian
Original description: Morgan, 1980, p. 22: Endoceratium exquisitum
Rounded triangular ambitus, two layered; apical horn, one lateral and one antapical horn strongly developed and distally rounded, second antapical and second lateral horn weakly developed; endophragm psilate, subtriangular; ectophragm subtriangular, with even bimodal perforations, 2-3 µm in diameter, and 0.5 µm in diameter wall layers in contact on dorsal and ventral surfaces, free elsewhere, resulting in an ambital pericoel 8-12 µm wide; nontabulate: archeopyle apical operculum free; accessory archeopyle sutures indicate six precingular plates and slightly notched sulcus indicating gonyaulacean tabulation.
Affinities:
Morgan, 1980, p. 22: Endoceratium exquisitum
E. exquisitum has a perforate ectophragm, while E. ludbrookii and E. dettmannii have a solid periphragm. E. dettmannii has large irregular dorsal and ventral areas of separation between the endophragm and periphragm. E ludbrookii either has the wall layers closely appressed, or with small areas of separation, often reflecting tabulation. Some specimens of Pseudoceratium turneri have a perforate ectophragm supported by numerous fibrous processes. This form probably develops into E. exquisitum by loss of the supporting processes.