Blackites aff. gladius (Locker, 1967) Varol, 1989 (Fig. 20L, M)

Rhabdosphaera gladius Locker, 1967: 766, pl. 1, fig. 1; pl. 2, fig. 12.

Blackites gladius – Varol 1989: 286.

DISTRIBUTION. — Blackites aff. gladius is only known from three records, one in Belgium, one in the Paris Basin and one in the Aquitaine Basin. It rarely co-occurs with Blackites inflatus in the Isnes quarry in SW Belgium, where its presence seems to be restricted to the top of the Brussel Sand Formation. A few specimens have been identified in the Donzacq Marl (upper NP14) at Saint-Geoursd’Auribat (Aquitaine Basin) (Lin et al. 2017) and in the upper part of the ‘Glauconie Grossière s.s.’ at Margival (Paris Basin, sample 3 in Steurbaut 1988), where it also co-occurs with B. inflatus . B. aff. gladius seems to indicate late Biochron NP14, also known as Biochon NP14b (sensu Berggren et al. 1995). It has not been recorded at the Mont-des-Récollets because of major erosion of the top of the Brussel Sand Formation in N France.

DISCUSSION

This medium-sized rhabdolith (c. 11 µm length) is marked by a very wide basal plate (c. 4.8 µm) and a lensiform stem, which maximum width is located in the upper half of the stem. The latter, which presents a basal collar, seems to be thin-walled (Fig. 20L) and rugose towards the top. These rhabdoliths bear great resemblance with those of B. gladius (Varol 1989: pl. 4, fig. 5; Bown 2005: pl. 21, figs 10-14). However, they differ by certain features of the stem, which is relatively longer and more slender in B. aff. gladius, especially in the top part, as well as by the position of its maximum width. The latter is less distal compared to its position in B. gladius .