Kjaerina (Villasina), 2016

Colmenar, Jorge, 2016, Ordovician rafinesquinine brachiopods from peri-Gondwana, Acta Palaeontologica Polonica 61 (2), pp. 293-326 : 311

Kjaerina (Villasina) sp. A

Fig. 11 .

Material.—Internal and external moulds of one ventral valve and two dorsal valves (MPZ 2015/1379–1381) from Portilla de Luna Limestone, upper Katian (Ka3–4), at Portilla de Luna (northwestern Spain).

Description.—Shells of medium size (largest specimen 27 mm wide), concavoconvex, semicircular to longitudinally elongated semioval in outline, or weakly alate in some specimens; maximum valve width at hinge line; slightly acute to rectangular cardinal angles. Ventral valve with moderately convex disc and dorsally directed geniculation. Ventral interarea planar, apsacline, 10% as long as valve length, delthyrium partially covered by apical pseudodeltidium. Dorsal valve with flat to concave disc; dorsal interarea anacline. Chilidium moderately convex, as long as interarea and medially grooved.

Radial ornament multicostellate with 7 ribs per 2 mm at 10 mm anteromedially from umbo, all of them with rounded crests; very coarse but weakly marked discontinuous rugation present in both external and internal moulds, over the disc of specimen of Fig. 11A .

Ventral interior with straight, short, blade-like dental plates; muscle field very well impressed, elongate, flabelliform about185% as long as wide and completely surrounded laterally by subparallel muscle bounding ridges.

Dorsal interior with divergent socket ridges bounding triangular dental sockets; bifid cardinal process with anteriorly divergent and posteroventrally directed triangular lobes. Strongly reduced notothyrial platform continuous anteriorly with broad median ridge. Shell structure pseudo-punctate.

Remarks.—The straight and thin socket ridges together with the triangular cardinal process lobes allow inclusion of this material to the subfamily Rafinesquininae . The multicostellate radial ornament, the valves with dorsally directed geniculation and the presence of rugation over the whole disc warrants the inclusion of this material to Kjaerina (Villasina) . Due to the low number of available specimens and its degree of fragmentation the species is left in open nomenclature.

Figures

Fig. 11. Rafinesquinine brachiopod Kjaerina (Villasina) sp. A; upper Katian (Ka3–4), Upper Ordovician; the Portilla de Luna Limestone, Cantabrian Zone, Spain. A. MPZ 2015/1379, internal mould (A1), latex cast of exterior (A2) and interior (A3) of a complete ventral valve. B. MPZ 2015/1380, latex cast of interior of an incomplete dorsal valve. C. MPZ 2015/1381, latex cast of interior of dorsal valve (C1), detail of cardinalia (C2). Scale bars 2 mm.