Hyocrinidae Carpenter 1884

Family Hyocrinidae Carpenter, 1884 Fig. 6F Undetermined genus and species Material examined: a single small columnal (OPH212). Description: columnal of heptagonal facet with radiate crenulae poorly preserved (Fig. 6F), diameter 0.75 mm, height 0.50 mm. Remarks: Heptagonal shape, or 7 crenular units on articular facets, is a frequent condition in hyocrinid columnals (Mironov & Sorokina, 1998; Roux & Lambert, 2011) but unknown in other extant stalked crinoid families. Moreover, symmetry 6–7 is more common in juvenile stalks and tends to disappear during growth by adjunction of new crenular units and generalization of circular articular facets. The small size of this columnal suggests that it belongs to a juvenile specimen which cannot be attributed at the genus rank.