Kjaerina (Kjaerina), 1929

Colmenar, Jorge, 2016, Ordovician rafinesquinine brachiopods from peri-Gondwana, Acta Palaeontologica Polonica 61 (2), pp. 293-326 : 297-298

Kjaerina (Kjaerina) sp. A

Fig. 4 .

1985 Hedstroemina sp. 1 ; Villas 1985: 110, pl. 29: 4, 7; pl. 30: 1, 4, 6. 1985 Hedstroemina ? sp. 2; Villas 1985: 111, pl. 30: 2, 3, 5, 7, 8.

Material.—Internal and external moulds of five ventral valves and one dorsal valve. MPZ 2015/1346, 1347, DPZ 368, 369, 372. Most of the specimens deformed by flattening. Lowermost Cystoid Limestone Formation at Alpartir 1 and Luesma 1 (see Villas 1985: figs. 2, 3 for exact location), Iberian Chains, Spain; upper Katian (Ka3–4 stage slices).

Description. —Shells of large size (largest specimen 46 mm wide), concavoconvex, semicircular in outline, or weakly alate in some specimens; maximum valve width normally at hinge line; slightly acute to rectangular cardinal angles. Ventral valve about 85% as long as wide; lateral profile with moderately convex disc and dorsally directed geniculation. Ventral interarea planar, apsacline, 10% as long as valve length. Dorsal valve with flat to concave disc; dorsal interarea anacline. Chilidium unknown.

Radial ornament parvicostellate with 8 ribs per 2 mm at 10 mm anteromedially from umbo, all of them with rounded crests; between two costae there are up to 6 costellae; prominent median costa present. Concentric ornamentation of irregular rugae covering the entire disc.

Ventral interior with strong, straight, short, blade-like dental plates; muscle field very well impressed, flabelliform, about 125% as long as wide and completely surrounded laterally by anteriorly convergent muscle bounding ridges. Diductor scars enclosing anteriorly lanceolate adductor scars.

Dorsal interior with thin, divergent socket ridges bounding triangular dental sockets; bifid cardinal process with anteriorly divergent, plate-like lobes. Strongly reduced anchor-shaped notothyrial platform continuous anteriorly with a short and narrow median ridge. Pseudopunctae thick, present in both valves coinciding with intercostal spaces and more developed posterolaterally to muscle scars.

Remarks. —All the external and internal characters of the studied specimens, the parvicostellate ornament with the prominent median costae, the rugae development, the ventral muscle field and the cardinalia, fit within Kjaerina

Kjaerina ), according to the emended diagnosis above. The dorsally directed geniculation clearly excludes this species from K. (Kjaerina) gondwanensis , the only other known Kjaerina species from the Mediterranean margin of Gondwana. Another character that allows to demarcate this material from all the other known K. ( Kjaerina ) species are the parallel-sided or even convergent anteriorly muscle bounding ridges. Most likely it is a new species but it is left in open nomenclature here because of the scarcity of material and its poor preservation (most of the specimens are deformed by flattening) until more and better-preserved material is found.

Figures

Fig. 4. Valves of rafinesquinine brachiopod Kjaerina (Kjaerina) sp. A.; upper Katian (Ka3–4), Upper Ordovician; Fombuena Formation at Alpartir (A, B, D) and Luesma (C, E), Iberian Chains, Spain. A. MPZ 2015/1346, latex cast of exterior of a complete and flattened ventral valve, showing the cardinal process lobes of the dorsal valve protruding in the vicinity of the hinge line. B. DPZ 368, internal mould of ventral valve. C. MPZ 2015/1347, internal mould of ventral valve, showing the convergent anteriorly muscle bounding ridges. D. DPZ 369, internal mould of ventral valve. E. DPZ 372, latex cast of interior (E1) and exterior (E2) of an incomplete dorsal valve. Scale bars 2 mm.