Kjaerina (Villasina) pedronaensis, Colmenar, 2016

Colmenar, Jorge, 2016, Ordovician rafinesquinine brachiopods from peri-Gondwana, Acta Palaeontologica Polonica 61 (2), pp. 293-326 : 306-307

Kjaerina (Villasina) pedronaensis sp. nov.

Figs. 8 , 9.

1927 Strophomena rhomboidalis Wilk. ; Vinassa de Regny 1927: 479, pl. 3: 40.

1948 Leptaena rhomboidalis ; Dreyfuss 1948: 39, pl. 7: 11.

1981 Leptaena sp. A ; Havlíček 1981: 26, pl. 6: 16.

Etymology: After the name of its type locality, the Punta Pedrona hill.

Type material: Holotype: MPZ 2015 /1363, internal mould of dorsal valve (Fig. 9A) . Paratypes: MPZ 2015 /1355–1362, MPZ 2015 /1364– 1371.

Type locality: Punta Pedrona hill ( Hammann and Leone 1997: see text-fig. 5 for exact location: Por 7), NE of Portixeddu, Province of Medio Campidano, Sardinia, Italy .

Type horizon: Greenish and grey silt and fine sandstone in tempestitic layers of the middle to upper part of the Portixeddu Formation, Katian.

Material.—Internal and external moulds of eight ventral valves and 16 dorsal valves from Sardinia ( Italy) and Montagne Noire ( France); MPZ 2015/1509–1515 from Punta

Pedrona, Gonnesa, VCR-14 (Sardinia) and Tranchée Noire (Montagne Noire) localities, Katian.

Diagnosis.— Kjaerina (Villasina) species with ventral valve disc slightly convex. Dorsal disc flat to concave; both, ventral valve and dorsal valve trails, inclined with respect to disc about 90°. Radial ornament with 7–8 ribs per 2 mm at 10 mm anteromedially from umbo; prominent median rib present; strong and irregular rugae covering the entire disc, better developed posterolaterally. Ventral muscle field elongate, flabelliform, very well impressed in adults; muscle bounding ridges curved inwardly. Cardinal process with concave myophores, engrossed posteroventrally during adult and gerontic stages; notothyrial platform strongly reduced.

Description.—Shell of medium size for the genus (largest specimen 37 mm wide), concavoconvex, semicircular in outline, or weakly alate in some specimens; maximum valve width at hinge line; slightly acute to rectangular cardinal angles. Ventral valve ranging 59–86% as long as wide (x = 71%; n = 4; σn = 0.10); lateral profile geniculate dorsally, with moderately convex disc, forming an angle about 90° with variably developed trail; ventral interarea planar, apsacline, delthyrium with apical pseudodeltidium. Dorsal valve with lateral profile geniculate dorsally, with flat to very slightly concave disc forming angle of about 90° with trail; dorsal interarea anacline; notothyrium filled completely by cardinal process; medially grooved convex chilidium covering the notothyrium completely.

Radial ornament multicostellate with 7–8 ribs per 2 mm at 10 mm anteromedially from umbo, all of them with rounded crests; prominent median costa often present. Concentric ornamentation of fila and strong irregular rugae, covering the entire disc but better developed on posterolateral sides of valves where they run oblique to hinge line.

Ventral interior with straight, short, blade-like dental plates extending forward 7–10% of valve length and with average dental plates divergence angle of 96° (range 75–114°; n = 6); muscle field very well impressed in adults, elongate, flabelliform ranging 8–50% as long as valve length, 10–37% as wide as maximum valve width and completely surrounded laterally by inwardly curved muscle bounding ridges.

Dorsal interior with strong socket ridges with divergence angle of about 75°, bounding triangular dental sockets. Cardinal process bifid with triangular lobes, posteroventrally directed, discrete during young stages, become engrossed posteroventrally and even reaching out to touch each other during adult and gerontic stages; mesocardinal ridge sometimes present between lobes (Fig. 9A 3). Strongly reduced anchor-shaped notothyrial platform, continuous anteriorly with median ridge dividing the poor-impressed dorsal muscle field. Both valves with moderately coarse pseudopunctae, regularly arranged all over the shell, coinciding with intercostal spaces.

Remarks.—This new Kjaerina (Villasina) species resembles K. (V.) almadenensis in many aspects. These species share features such as the ornamentation and the concave myophores, but they clearly differ in the geniculation development. The discs of both valves in K. (V.) pedronaensis are almost flat and make a sharp angle of about 90° with the trail whereas in K. (V.) almadenensis the inflexions between the convex discs and the trails are rounded. Kjaerina (V.) pedronaensis differs from K. (V.) meloui in having stronger rugae and geniculation, and lower ribs density. Vinassa de Regny (1927) assigned one valve from Portixeddu to Strophomena rhomboidalis . This shell shares all the characters with the new species described here, K. (V.) pedronaensis , so it is included herein in the synonymy of this species. Havlíček (1981: pl. 6: 16) figured a fragmented and poorly preserved ventral valve exterior as Leptaena sp. A . A larger sampling in the same levels of this formation has provided several specimens ( Figs. 8G , 9C). This material has the same rib density, rugae development, ventral muscle field outline and cardinal process shape and thickening as those of type material of this new species, so I decided to include this material within K. (V.) pedronaensis .

Stratigraphic and geographic range.— In addition to the type locality K. (V.) pedronaensis occurs in the following localities: Sa Siliqua hill (locality Gon 1; Hammann and Leone 1997) and 900 m E-NE of Portixeddu ( VCR/14 field number) both Portixeddu Formation , Katian , Sardinia ( Italy); Tranche Noire , Gabian Formation , middle– upper Katian, Montagne Noire ( France) .

Figures

Fig. 8. Ventral valves of rafinesquinine brachiopod Kjaerina (Villasina) pedronaensis sp. nov.; Katian, Upper Ordovician; Portixeddu Formation at Punta Pedrona (A), Gonnesa (B–E), and VCR/14 (F), Sardinia, Italy; Gabian Formation at Tranchée Noire, Montagne Noire, France (G, H). A. MPZ 2015/1355, paratype, ventral internal mould (A1) and latex cast of ventral interior (A2) of an incomplete valve. B. MPZ 2015/1356, paratype, latex cast of ventral exterior. C. MPZ 2015/1357, paratype, internal mould. D. MPZ 2015/1358, paratype, internal mould. E. MPZ 2015/1359, ventral internal mould (E1) and latex cast of ventral exterior (E2). F. MPZ 2015/1360, internal mould of an incomplete valve. G. MPZ 2015/1361, internal mould of an incomplete valve. H. MPZ 2015/1362, latex cast of exterior. Scale bars 2 mm.