Punkaster ruegenensis gen. et sp. nov.

urn:lsid:zoobank.org:act: 9762A572-434A-4D16-86F8-644D05201BC4

Fig. 12A–I, L–M

Diagnosis

Punkaster gen. nov. in which the proximal supero- and inferomarginals form fused pairs; distally, they are separate. Large marginal spine bases absent.

Etymology

Named after the island of Rügen (northeast Germany) in the Baltic Sea.

Material studied

The interradial marginal pair (Fig. 12A) is the holotype (SNSB-BGSP 2020 XLV 31); the other eight ossicles illustrated here are paratypes (SNSB-BGSP 2020 XLV 32–39), all from the upper lower Maastrichtian Chalk of Rügen, northeast Germany. Additional material includes over 30 marginal ossicles and other ossicles from the same locality (lot SNSB-BGSP 2020 XLV 32).

Description

Proximal marginals fused, bilobed; actinal part formed by a low, elongated, concave inferomarginal, abactinal part a subrectangular flange, formed by superomarginal (Fig. 12A–E, H–I). Infero- and superomarginals separated by a notch of variable size. Proximal/distal profile L-shaped, articulation facets for adjacent marginal plates oval (Fig. 12D). External sculpture of coarse reticulate stereom network, with rugosities, and small cylindrical projections which carried spines. Distal inferomarginals (Fig. 12F–G) rectangular, elongated, with similar sculpture to proximal plates. Presumed adambulacral (Fig. 12L–M) boot-shaped, with deep podial notch and narrow distal portion. Large fs bases present, central actinal face slightly inset, coarsely reticulate, rugose.

Remarks

The marginal ossicles are most unusual in that supero- and inferomarginal pairs are fused, perhaps uniquely amongst asteroids. The overall shape and sculpture of the ossicles suggest affinity with the type species, Punkaster spinifera gen. et sp. nov. (see above), but the present form differs in the fused proximal marginals and in the absence of large spine bases.