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Hystrichosphaeridium prolatum
Holotype. Plate 2, figure 16; GSCA slide no. P51263-05 (¼GSCC slide no. P5205-156H); coordinates 3.5x91.2; EF intersection of Y56/circle with Y56/1 and Y56/3; Nunavut Palaeontology Collection no. NUPB 988; Q section, Twosnout creek, Bylot Island. Bylot Island formation.
Etymology. The epithet is from the Latin prolatus meaning extended, elongated, in reference to the shape of the central body.
Diagnosis. A species of Hystrichosphaeridium having a distinctly elongate central body, its length considerably exceeding its width. The processes are similar to those in Hystrichosphaeridium tubiferum in that they vary in width according to their position in relation to the paratabulation, with the slenderest being the sulcals followed by the paracingulars and the apicals. Process endings show considerable variability, ranging from undulate to aculeate, with some being distinctly quadrate, as in Hystrichosphaeridium quadratum; some are perforate.
Comments. The taxon Hystrichosphaeridium tubiferum subsp. ovale Marheinecke 1992 is similar to Hystrichosphaeridium prolatum. Hystrichosphaeridium prolatum is essentially identical to Hystrichosphaeridium quadratum but is elongate. The variation in shape may reflect palaeoenvironmental control. Importantly, Hystrichosphaeridium prolatum has a shorter stratigraphic range than Hystrichosphaeridium quadratum.
Size. Holotype: central body length 38um, central body width 33um; processes up to 22um. Range of eight specimens: central body length 29–66um, central body width 17–66um, process length up to 18um, process width up to 6um.
Age. Santonian to late Campanian.
Etymology. The epithet is from the Latin prolatus meaning extended, elongated, in reference to the shape of the central body.
Diagnosis. A species of Hystrichosphaeridium having a distinctly elongate central body, its length considerably exceeding its width. The processes are similar to those in Hystrichosphaeridium tubiferum in that they vary in width according to their position in relation to the paratabulation, with the slenderest being the sulcals followed by the paracingulars and the apicals. Process endings show considerable variability, ranging from undulate to aculeate, with some being distinctly quadrate, as in Hystrichosphaeridium quadratum; some are perforate.
Comments. The taxon Hystrichosphaeridium tubiferum subsp. ovale Marheinecke 1992 is similar to Hystrichosphaeridium prolatum. Hystrichosphaeridium prolatum is essentially identical to Hystrichosphaeridium quadratum but is elongate. The variation in shape may reflect palaeoenvironmental control. Importantly, Hystrichosphaeridium prolatum has a shorter stratigraphic range than Hystrichosphaeridium quadratum.
Size. Holotype: central body length 38um, central body width 33um; processes up to 22um. Range of eight specimens: central body length 29–66um, central body width 17–66um, process length up to 18um, process width up to 6um.
Age. Santonian to late Campanian.