Kjaerina (Villasina) almadenensis ( Villas, 1995 )

Colmenar, Jorge, 2016, Ordovician rafinesquinine brachiopods from peri-Gondwana, Acta Palaeontologica Polonica 61 (2), pp. 293-326 : 300-304

Kjaerina (Villasina) almadenensis ( Villas, 1995)

Figs. 5, 6.

1908 Strophomena rhomboidalis Wilkens ; Delgado 1908: 31, 60. 1908 Strophomena deltoidea Conrad ; Delgado 1908: 60. 1985 Hedstroemina mundae (Sharpe, 1853) ; Young 1985: pl. 34: 10

(non figs. 1–9, see remarks to Rafinesquina [ Mesogeina ] pseudoloricata below). 1985 Hedstroemina sp. B ; Young 1985: 348, pl. 35: 1–14.

1995 Hedstroemina almadenensis sp. nov.; Villas 1995: 81, pl. 13: 8–13.

Holotype: MPZ 11570 , internal and external moulds of dorsal valve,

re-illustrated here in Fig. 2A.

Type locality: Al-1 locality, Almaden, Central Iberian Zone.

Type horizon: Calcareous sandstones of the uppermost “Bancos Mixtos”.

Material.—Internal and external moulds of 30 ventral valves and 18 dorsal valves from the Spanish and Portuguese Central Iberian Zone and the Armorican Massif ( France), uppermost upper Berounian (probably Ka2 stage slice, Katian).

Emended diagnosis. —Species of Kjaerina (Villasina) with ventral valve disc moderately convex; trail inclined with respect to disc 110–120°. Dorsal valve disc concave; trail inclined with respect to disc about 120°. Radial ornament with 6–8 ribs per 2 mm at 10 mm anteromedially from umbo; prominent median riboccasionally present; regular and continuous development of rugae. Ventral muscle field well impressed, flabellate. Cardinal process lobes, triangular in young specimens and extremely engrossed in adult and gerontic ones; myophores with concave and striated posteroventral surface; notothyrial platform strong; median ridge wide and high; broad transmuscle septa longer than median ridge.

Description.—Shell of medium size for the genus (largest specimen 36 mm wide), strongly concavoconvex, both valves geniculate dorsally, alate to semicircular in outline; maximum valve width at hinge line in young specimens and slightly anteriorly in adult ones; slightly acute cardinal angles in young stages and rectangular to obtuse cardinal angles in adult stages; rectimarginate anterior commissure. Ventral valve ranging 71–87% as long as wide (x = 79%; n = 5); lateral profile strongly geniculate dorsally, at approximately 20 mm long growth stage, with convex disc and trail of variable length inclined with respect to disc 110–120°; ventral interarea long, flat, apsacline with apical pseudodeltidium. Dorsal valve about 80% as long as wide; lateral profile strongly geniculate dorsally with moderately concave disc, trail of variable length inclined with respect to disc about 120°; dorsal interarea long, flat, anacline, notothyrium filled completely by cardinal process; medially grooved convex chilidium as long as dorsal interarea length, covering up to 50% of cardinal process lobes.

Radial ornament multicostellate with 6–8 ribs per 2 mm at 10 mm anteromedially from umbo; weakly prominent median costa not always present. Concentric ornamentation of fila, irregular but relatively continuous rugae with

Fig. 3. Dorsal valves of rafinesquinine brachiopod Kjaerina (Kjaerina) gondwanensis sp. nov.; lower–middle Katian (Ka1-2), Upper Ordovician ; → Portixeddu Formation at Gonnesa , Sardinia, Italy (A–E); Glauzy Formation at Grand Glauzy hill, Montagne Noire, France (F–J). A. MPZ 2015 /1339, paratype, latex cast of dorsal interior (A 1) and detail of cardinalia of an incomplete specimen in anteroblique (A 2), posteroblique (A 3), and lateroblique

A 4) views. B. MPZ 2015 /1340, paratype, latex cast of interior (B 1) and internal mould (B 2). C . MPZ 2015 /1341, paratype, latex cast of dorsal exterior of an incomplete specimen. D . MPZ 2015 /1342, paratype, latex cast of interior (D 1) and detail of cardinalia in anteroblique (D 2) and upper (D 3) views, showing the posteroventrally engrossed cardinal process lobes of a dorsal valve. E . MPZ 2015 /1343, paratype, latex cast of interior (E 1) and detail of cardinalia (E 2), showing the mesocardinal ridge supporting the chilidium. F–H. Paratypes, latex casts of dorsal interior of an incomplete specimens .

F. MNHN.F.A46456. G. MPZ 2015 /1344. H. MNHN.F.A46453. I. MPZ 2015 /1345, paratype, latex cast of dorsal exterior of an incomplete specimen.

. VOMN-2200 , paratype, latex cast of dorsal exterior of a complete specimen. Scale bars 2 mm .

wave length of about 1 mm, which on posterolateral sides of valves run oblique to hinge line.

Ventral interior with short, thin, blade-like dental plates extending forward approximately 8% of valve length and average dental plates divergence angle of 107° (range 99– 116°; n = 4), continuous anteriorly with less divergent muscle bounding ridges only developed in largest specimens; muscle field flabellate ranging 23–38% as long as valve length, approximately as long as wide and traversed by fine radial ridges; adductor scars ranging 25–30% as wide as muscle field maximum width; well developed myophragm located posteriorly to adductor scars.

Dorsal interior with strongly thickened cardinal process lobes in adult stages and myophores with concave and striated posteroventral surface; socket ridges ankylosed to posterolateral edges of strong anchor-shaped notothyrial platform continuous anteriorly with wide, high median ridge, bisecting deeply impressed adductor scars, traversed by broad transmuscle septa longer than median ridge. Both valves with coarse pseudopunctae, regularly arranged anteromedially coinciding with intercostal spaces and irregularly disposed posterolaterally.

Remarks.—This species was originally assigned to Hedstroemina by Villas (1995), who remarked its multicostellate radial ornament contrasting with the unequally parvicostellate H. fragilis (= K. [H.] fragilis ). He considered the ornamentation as a specific character. Nevertheless, as discussed under the remarks of K. (Villasina) above, this character is considered herein as key subgeneric feature, and H. almandenensis is included within K. (Villasina). It is the species with the thickest cardinal process lobes within the subgenus. Also it has the most regular and continuous pattern of rugation, so its discrimination from the new species, introduced below, is very clear. Young (1985) assigned several valves from the Porto de Santa Anna Formation (Portuguese Central Iberian Zone) to an indeterminate species of Hedstroemina . Villas (1995), in his description of H. almadenensis from the uppermost “Bancos Mixtos” of the Spanish Central Iberian Zone, did not compare it with the material from Portugal. Now, after having studied both collections, I consider that the material from the Porto de Santa Anna Formation and the Spanish material belong to the same stock. In the same way, I include within this species material from the lower and middle part of the Rosan Formation of the Armorican Massif, due to the similarities in shell outline, ornamentation and ventral muscle field (Fig. 5H, K).

Fig. 5. Ventral valves of rafinesquinine brachiopod Kjaerina (Villasina) almadenensis ( Villas, 1995) ; middle Katian (Ka2), Upper Ordovician; “Bancos → Mixtos” Formation at Almadén (A–D), Spanish Central Iberian Zone, Spain; Porto de Santa Anna Formation at Louredo; Portuguese Central Iberian Zone , Portugal (E–G, I, J); lower part of Rosan Formation at Pointe de l’Aber , Armorican Massif, France (H, K). A. MPZ-11573 , paratype, internal mould (A 1) and latex cast of exterior (A 2). B. MPZ 2015 /1348, topotype, internal mould of a small valve showing the well developed median rib. C. MPZ-11574 , paratype, ventral internal mould (C 1) and latex cast of interior (C 2), showing detail of dental plates. D. MPZ 2015 /1349, topotype, latex cast of exterior of a small valve .

E. IGM- 3009A, latex cast of exterior. F. IGM- 3006, internal mould of a small valve. G. IGM- 3011, internal mould. H. MPZ 2015/1351, ventral internal mould (H 1) and latex cast of ventral exterior (H 2). I. IGM- 3009B, latex cast of exterior. J. IGM- 3005, ventral internal mould (J 1) and latex cast of ventral interior (J 2), showing detail of dental plates. K. MPZ 2015/1352, latex cast of exterior (K 1) and internal mould (K 2) of a small valve. Scale bars 2 mm.

Stratigraphic and geographic range.—Spanish Central Iberian Zone ( Spain): Uppermost “Bancos Mixtos” at Fh 1 Jabalón river section), Al-1 (Almadén), and Co-I (Corral de Calatrava) Hammann’s (1976) localities, middle Katian (Ka2 stage slice); Portuguese Central Iberian Zone ( Portugal): Porto de Santa Anna Formation at Louredo locality, middle Katian (Ka2 stage slice); Armorican Massif ( France): lower part of Rosan Formation at Pointe de l’Aber locality, Katian.