Kjaerina (Villasina), 2016

Colmenar, Jorge, 2016, Ordovician rafinesquinine brachiopods from peri-Gondwana, Acta Palaeontologica Polonica 61 (2), pp. 293-326 : 298-300

Subgenus Kjaerina (Villasina) nov.

Etymology: Subgenus dedicated to Enrique Villas for his contributions in the study of the Late Ordovician brachiopods.

Type species: Kjaerina (Villasina) pedronaensis sp. nov.; middle to upper part of the Portixeddu Formation, Katian , Sardinia .

Species included: Hedstroemina almadenensis Villas, 1995 , uppermost Bancos Mixtos”, middle Katian (Ka2 stage slice), Spanish Central Iberian Zone; Kjaerina (Villasina) meloui sp. nov., Tufs et Calcaires of the Rosan Formation, upper Katian (Ka3–4), Armorican Massif; Kjaerina (Villasina) pyrenaica sp. nov., Cavá Formation, lower–middle Katian (Ka1–2), Spanish Pyrenees.

Diagnosis. —Species of Kjaerina with longitudinal profile always geniculate dorsally. Radial ornament multicostellate. Concentric ornament consisting of more or less regular rugae normally covering the entire disc. Diductor scars not enclosing anteriorly adductor scars. Cardinal process lobes become extremely engrossed in some species during adult and gerontic stages.

Remarks.—Ornamentation is a character normally used to differentiate species. Nevertheless, sometimes it is also used as a key character at higher taxonomic levels. It is the case of the rugation used to distinguish between the subfamilies Rafinesquininae and Leptaeninae ( Cocks and Rong 2000) . Rong and Cocks (1994) in their revision of the strophomenoids, only conditionally accepted variations in the ornament as a valid character for generic and subgeneric differentiation. This is a logical criterion applied usually in all brachiopod groups, although occasionally in many brachiopod stocks and families, genera that differ exclusively in their ornamentation can be found ( Cooper 1969). The ornamentation within the subfamily Rafinesquininae seems to be a good diagnostic character to demarcate genera because it allows to identify groups of species having a common ancestor.

Most of the genera in Rafinesquininae are unequally parvicostellate. Only Megamyonia Wang, 1949 from the Katian of North America, Testaprica Percival, 2009 from the Katian of central New South Wales, Australia, and Shuangheella Zhan and Jin, 2005 from the lower to middle Dapingian of China, are different in this respect and display multicostellate shells. Villas (1995), in erecting Hedstroemina almadenensis from the Upper Ordovician of central Spain considered its multicostellate ornamentation as a specific character, separating it from the parvicostellate type species H. fragilis . However, after a study of larger sample of rafinesquinins from several Upper Ordovician Mediterranean localities, it becomes evident that there was a radiation in the family during that time, spreading throughout the Mediterranean margin of Gondwana a close-knit group of multicostellate species, where H. almadenensis belongs to. This almost simultaneous occurrence of closely related and sharing an unusual ornamentation species in a previously almost uninhabited by this family region points to a common origin that merits taxonomic recognition. Nevertheless, considering the current reluctance to give generic significance to differences in the strophomenoid ornamentation ( Rong and Cocks 1994), the Mediterranean spe-

Fig. 2. Ventral valves of rafinesquinine brachiopod Kjaerina (Kjaerina) gondwanensis sp. nov.; lower–middle Katian (Ka1–2), Upper Ordovician ; → Portixeddu Formation at Gonnesa , Sardinia, Italy (A–C); Gabian Formation at Tranchée Noire (D) and Glauzy Formation at Grand Glauzy hill (E–I), Montagne Noire, France. A. MPZ 2015 /1335, holotype, latex cast of exterior (A 1), internal mould (A 2), and interior (A 3). B. MPZ 2015 /1336, paratype, latex cast of ventral exterior (B 1), internal mould (B 2), and detail of the ventral muscle scar (B 3), showing the posterolateral pseudopunctae arrangement of a large specimen. C. MPZ 2015 /1337, paratype, latex cast of ventral exterior. D. MPZ 2015 /1338, internal mould (D 1) and latex cast of ventral exterior D 2). E. MNHN.F.A46450, latex cast of ventral exterior (E 1) and internal mould (E 2), showing incipient geniculation. F. MNHN.F.A46454, paratype, latex cast of ventral exterior. G. MNHN.F.A46451, paratype, latex cast of ventral exterior. H. MNHN.F.A46452, paratype, internal mould showing rugation all over the ventral valve. I. MNHN.F.A46455, paratype, latex cast of ventral exterior showing a well developed median rib. Scale bars 2 mm .

cies described below, close to H. almadenensis , are proposed to be grouped within a new subgenus Kjaerina (Villasina) .

The concentric ornament of the studied material, consisting of irregular rugae sometimes covering the entire disc, sometimes restricted posterolaterally, as well as the bifid triangular cardinal process lobes, the straight socket ridges welded to the anchor-shaped notothyrial platform, continuous anteriorly with a median ridge, warrants its inclusion within the subfamily Rafinesquininae . Furthermore, the absence of a peripheral ridge and of socket ridges inwardly curved to bound the dorsal muscle scars, demarcates the studied material from the subfamily Leptaeninae , in spite of its well developed dorsally directed geniculation.

The material under discussion is very similar in many aspects to Kjaerina (Kjaerina) and Kjaerina (Hedstroemina) , e.g., in displaying similar variable rugation as well as occasional dorsally directed geniculation. Nevertheless, its multicostellate ornamentation (Fig. 9D) allows a ready differentiation from these unequally parvicostellate subgenera.

The new subgenus also strongly recalls Kjerulfina Bancroft, 1929 , but its shell is geniculate in dorsal direction, instead of the ventrally directed geniculation in Kjerulfina .

Kjaerina (Villasina) differs from Megamyonia , one of the other three multicostellate rafinesquinines, in its geniculate profile, in not having ventral transmuscle septa and in having much better developed socket ridges. It differs from Testaprica , also multicostellate, by its concavo-convex profile whereas the latter genus is convexo-concave to convexo-planar, or even resupinate ( Percival 2009).

Finally K. (Villasina) differs from Shuangheella in having a concavo-convex profile with very convex ventral valves, whereas Shuangheella is plano-convex with a very gently convex ventral valve. In addition, K. (Villasina) differs from Shuangheella in having a dorsal median ridge, absent in the latter, and in having straight socket ridges instead of the curved posterolaterally socket ridges of Shuangeella. The curved posterolaterally socket ridges is a feature typical of the family Strophomenidae , thus Shuangheella fits better within that family than in the subfamily Rafinesquininae .