Bathycrinus sp.

Roux, Michel, Thuy, Ben & Gale, Andy S., 2025, Plio-Pleistocene deep-sea crinoid (Echinodermata) diversity from the western Rodrigues Ridge, Indian Ocean, revealed by microfossil evidence, Zootaxa 5583 (3), pp. 509-525 : 518-519

? Bathycrinus sp.

Fig. 6A–B

Material examined: one basal circlet ( OPH210 ) , two axillary brachial (IBr2ax) ( OPH211 ) .

Description: Basals fused, aboral face slightly concave with an irregular radiate crenularium ( Fig. 6A ), adoral face convex slightly granulose without trace of pentagonal symmetry or nervous canal lumen and wide perilumen flat without granulation ( Fig. 6B ); adoral diameter 1.47 mm, aboral diameter 1.02 mm, height 1.91 mm. Axillary brachial (IBr2ax) with aboral surface smooth, adoral face poorly preserved having a marked axial groove ( Fig. 6D ), height 1.91 mm, maximum width 1.85 mm and proximal width 1.00 mm. Another similar but smaller IBr2ax with maximum width 1.30 mm.

Remarks: The shape of the basal ring and the absence of a conspicuous lumen of interradial nervous canals on the adoral face is usual in Bathycrinus , which sometimes shows a discrete pentalobate figure like in B. carpenteri (Danielssen & Koren 1877) ( Fig. 4C ). The radiate crenularium on the basal ring adoral face or on the proximal columnal facets has never been observed in bathycrinids and rhizocrinids. Monachocrinus differs in having free basals with conspicuous interradial nervous canal open on adoral face (Roux, in preparation). The adoral face of IBr2ax resembles those of Monachocrinus ( Fig. 6E ), but unfortunately the material is too poorly preserved for a more conclusive comparison. Pending additional material, the two ossicles described above are attributed to? Bathycrinus sp.

Figures

FIGURE 4. Brachials of Porphyrocrinus. A–B, D–E, G–H: OPH204, P. polyarthra from site RR13A, A–B: same proximal brachial of a pair, D,E,H: same distal brachial of a pair, G: distal brachial of another pair; C, F, I: P. thalassae from Bay of Biscay (NE Atlantic), A–C: trifascial facets of ligamentary articulations; D–F: distal brachials of a pair with muscular synarthry; H–I: spines on aboral side surface; A–F: more or less oblique distal views; G: adoral side view; H–I: aboral side views. Scale bars equal 0.2 mm.

FIGURE 6. Bathycrinid and hyocrinid ossicles. A–B, D, F: from site RR13A on the western Rodrigues Ridge; A–C: basal circlets, A–B: Bathycrinus sp., OPH210, A: aboral facet, B: adoral facet, C: oblique proximal view, extant B. carpentieri from Norvegian sea; D–E: axillary primibrachial (IBr2ax), D: Bathycrinus sp., OPH211, E: Monachocrinus recuperatus, from NE Atlantic; F: hyocrinid columnal, OPH212. Scale bars equal 0.2 mm.