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Hystrichosphaeridium quadratum

From Fensome et al., 2019:
Hystrichosphaeridium quadratum Fensome et al. 2016b, p.50, pl.8, figs.17–19. Holotype: Fensome et al., 2016b, pl.8, figs.17–18. Age: last occurrence, early Ypresian.
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Original description Fensome et al., 2016b:

Holotype. Plate 8, figs 17, 18, from a cuttings sample at 2770–2780 m in Gilbert F-53, GSC type collection no. 137988, sample P39505, slide 01, co-ordinates 11.3 × 99.2, England Finder L29/3. Diameter of central body 44 μm, length of processes up to about 37 μm. The age determined for the sample from which the holotype was recovered is early Ypresian.

Etymology. From the Latin quadratus (four-cornered), in reference to the rectangular distal endings of the processes in this species.

Diagnosis. A species of Hystrichosphaeridium in which the distal process endings are slightly flared and polygonal, generally rectangular and commonly perforate. The process bases are mesotabular and circular.

Size. Width of central body 36‒48 μm, length of central body (when operculum in place) 46‒63 μm; processes up to 39 μm long. Six specimens measured.

Age. LO: Selandian. Not plotted.

Remarks. This species differs from Hystrichosphaeridium tubiferum in having rectangular endings to its processes. It also resembles Hystrichokolpoma proprium,
but the holotype of that species has rounded polygonal process bases that largely fill the plate (see Fauconnier & Masure 2004, plate 40, figs 1–3), as is typical of the genus Hystrichokolpoma. Hystrichos phae ridium salpingophorum differs in lacking perforations in the distal endings of the processes.
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