Rafinesquina (Mesogeina) pomoides Havlíček, 1971

Colmenar, Jorge, 2016, Ordovician rafinesquinine brachiopods from peri-Gondwana, Acta Palaeontologica Polonica 61 (2), pp. 293-326 : 316-318

publication ID	https://doi.org/ 10.4202/app.00102.2014
persistent identifier	https://treatment.plazi.org/id/DE6FAC27-FFC3-625A-FFEA-5475FAF8BB38
treatment provided by	Felipe
scientific name	Rafinesquina (Mesogeina) pomoides Havlíček, 1971
status

Treatment

Figs. 15 View Fig , 16 View Fig .

1971 Rafinesquina pomoides sp. n.; Havlíček 1971: 71, pl. 22: 4–5; pl. 23: 2.

1979 Strophonema sp.; Hafenrichter 1979: pl. 9: 9.

1983 Rafinesquina aff. pseudoloricata ; Villas 1983: pl. 3: 5–7.

1985 Rafinesquina lignani sp. nov.; Villas 1985: 105, text-figs. 11–13; pl. 24: 11–13; pl. 24: 1–6; pl. 25: 1–8; pl. 26: 1–6; pl. 27: 1–6.

1985 Hedstroemina sp. aff. mundae (Sharpe, 1853) ; Young 1985: 343, pl. 33: 6–12.

2006 Rafinesquina? pomoides Havlíček ; Villas et al. 2006: figs. 4.5, 4.7, 4.8.

2007 Rafinesquina pomoides Havlíček, 1971 ; Álvaro et al. 2007: fig. 6C.

Holotype: Internal mould of ventral valve ( Havlíček 1971: pl. 22: 4).

no specimen number in original publication].

Type locality: Jbel Ahchahach, Anti Atlas, Morocco.

Type horizon: Upper Tiouririne Formation.

Material.— Internal and external moulds of 42 ventral valves and 11 dorsal valves: DPZ- 318, 354b, 354b’, 356 from the Iberian Chains and Spanish Central Iberian Zone; MPZ 2003/832, 833, 843 from the Anti Atlas, Morocco; MPZ 2015/1390 and IGM- 2545A-B, 2945 from the Portuguese Central Iberian Zone; middle Katian (Ka2).

Emended diagnosis. —Species of Rafinesquina (Mesogeina) with shell approximately as wide as long. Ventral valve very convex with strong dorsal geniculation. Radial ornament with 8–10 ribs per 2 mm at 10 mm anteromedially from umbo. Ventral muscle field large, flabellate, poorly impressed anteriorly. Cardinal process lobes ponderous, triangular in outline, with flat and striated posteroventral surface; anchor-shaped notothyrial platform, high, well developed.

Description.—Shell of large size (largest specimen 38 mm wide), with strongly dorsal geniculation; semicircular in outline; maximum valve width at hinge line or slightly anterior to it; cardinal angles from acute to obtuse. Ventral valve ranging 82–123% as long as wide (x = 104%; n = 30; σn = 0.11); lateral profile geniculate dorsally, at approximately 25 mm long growth stage, with very convex disc and with variable trail length, ranging from 15% as deep as long in juvenile specimens and up to 40% as deep as long in adult ones (x = 27%; n = 28; σn = 0.06). Ventral interarea curved, apsacline, 8% as long as valve length; delthyrium open. Dorsal valve ranging 80–105% as long as wide (x = 96%; n = 7; σn = 0.09), gently concave; dorsal interarea anacline, 4% as long as valve length; notothyrium completely covered by a medially grooved, convex chilidium.

Radial ornament unequally parvicostellate with 8–10 ribs per 2 mm at 10 mm anteromedially from umbo, all of them with angular crests; ribs as wide as the intercostal spaces; between two costae there are up to 6 costellae. Concentric ornamentation consisting of fine fila disposed over the whole shell, as well as of more prominent growth lines occurring at different lengths from umbo but closer to each other, near shell margin; some specimens show evidences of shell damage, reflected as discontinuities in shell ornament ( Figs. 15E View Fig , 16B View Fig ).

Ventral interior with strong teeth well differentiated from hinge line, dental plates extending forward approximately 12% of valve length and with average dental plates divergence angle of 88° (range 80–94°; n = 6); muscle field poorly impressed anteriorly, flabelliform, ranging 24–55% as long as valve length, about 120% as long as wide and surrounded posterolaterally by narrow and thin muscle bounding ridges. Adductor scars lanceolate, about 15% as wide as muscle scars, completely surrounded by diductors.

Dorsal interior with strong and divergent socket ridges (x = 109°; n = 3) bounding triangular dental sockets; bifid cardinal process with elongate or plate-like lobes in young specimens, but triangular in outline and ponderous in adult specimens. Lobes weakly divergent anteriorly, with striated posteroventral surface of myophores. Situated on well developed, high, anchor-shaped notothyrial platform, continuous anteriorly with broad and well developed median ridge, halving subcircular dorsal muscle field; short transmuscle septa sometimes present in most posterior part of the muscle scars. Pseudopunctae with radial pattern visible in both interiors, but better marked in ventral ones.

Remarks.—This species was described by Havlíček (1971) based on a small collection from Morocco. Villas et al. (2006) and Álvaro et al. (2007), considered tentatively Rafinesquina (Mesogeina) pomoides as a senior synonym of the Spanish species R. (Mesogeina) lignani Villas, 1985 . Following these authors and once confirmed the complete morphological similitude between both species, with the study of a new large collection from Mococco, I propose to synonymize them formally, being R. (Mesogeina) pomoides the senior synonym. Also some specimens classified by Young (1985: pl. 33: 6–12) as Hedstroemina sp. aff. mundae (Sharpe in Ribeiro et al., 1853), after examination of a large collection of these brachiopods from Portugal, belong to R.

Mesogeina ) pomoides , although the dorsal valves of the

Portuguese shells remain unknown.

Stratigraphic and geographic range.—Katian of Morocco: middle part of Lower Ktaoua Formation at Jbel Ahchach Havlíček, 1971); upper part of Lower Ktaoua Formation at Alnif ( Villas et al. 2006; Alvaro et al. 2007) and Upper Tiouririne Formation at Jbel Adrar, Jbel Aroudane, and Jbel Tizi N’Rsoa; Portuguese Central Iberian Zone: Porto de Santa Anna Formation at Zuvinhal locality ( Portugal); Spain:

middle part of Huerva Member of the Fombuena Formation at Luesma 2, Fombuena 4, and Herrera 1 localities (see Villas 1985 for precise situation) from the Iberian Chains; “Bancos mixtos” at Corral de Calatrava ( Hafenrichter 1979; Villas, 1995) from the Spanish Central Iberian Zone.