Bairdia (Cryptobairdia) cf. singularis Krömmelbein, 1954

Maillet, Sebastien, Milhau, Bruno, Vreulx, Michel & Posada, Luis-Carlos Sánchez De, 2016, Givetian ostracods of the Candás Formation (Asturias, North-western Spain): taxonomy, stratigraphy, palaeoecology, relationship to global events and palaeogeographical implications, Zootaxa 4068 (1), pp. 1-78 : 54

Bairdia (Cryptobairdia) cf. singularis Krömmelbein, 1954

(Pl. IV: Fig. 6 )

cf. 1954a Bairdia singularis nov. sp.; Krömmelbein: 248, pl. 1, fig. 1.

cf. 1965a Bairdia (Cryptobairdi a) cf. singularis Krömmelbein ; Becker: 421, pl. 35, fig. 6. cf. 1979 Bairdia (Cryptobairdi a) cf. singularis Krömmelbein ; Olempska: 104, pl. 19, fig. 5. 2013 Bairdia (Cryptobairdia) aff. singularis Krömmelbein ; Maillet: 162, pl. XXV, fig. 12. non 2013 Bairdia (Cryptobairdia) aff. singularis Krömmelbein ; Maillet: 162, pl. XXV, figs. 9–11. non 2013 Bairdia (Cryptobairdia) cf. singularis Krömmelbein ; Maillet: 162, pl. XXV, fig. 13.

Material. 26 specimens (25 C, 1 V).

Description. Medium-sized elongated carapace, subhexagonal in lateral view, biconvex in dorsal view. Overlap of the larger LV over the RV along the whole outline, slighter in the antero-ventral part. Bow-shaped projection in ventral view. Hmax at 1/3 posterior; Lmax slightly dorsal; Wmax slightly posterior. Dorsal margin straight in its middle part and anteriorly and posteriorly oblique (slightly concave anteriorly). Ventral margin concave in its middle part and convex anteriorly and posteriorly, becoming more arched at its extremities. Dorsal and ventral margins almost parallel. Anterior margin slightly concave in its dorsal part to the anterior end point about at 1/3 dorsal of Hmax, and, from this point, convex in its ventral part. Posterior margin oblique in its dorsal part to the posterior end point (posterior Lmax point), and from this point, regularly convex in its ventral part. Anterior and posterior ends sharp. Carapace flattened in its ventral part along the posterior and anterior margins. Anterior end of the carapace higher than the posterior one. Anterior part of the carapace slightly higher than the posterior one. Surface smooth.

Discussion. These specimens remind Bairdia (Cryptobairdia) singularis Krömmelbein, 1954 . However, the carapace of our specimens is more symmetrical, with an overlapping of the valves more pronounced, and straighter anterior and posterior oblique parts of the dorsal margin. Regarding a possible intraspecific variability, they could be the same species.

Occurrences. Lower Givetian (Hanonet and Trois-Fontaines Fms), Ardenne (Mont d’Haurs section); Middle Givetian (Candás Fm, mbs A, B and C), Asturias (Peran-Perlora section).

Figures

FIGURE 6. Faunal relations and Middle Devonian palaeogeographic reconstruction. Abbreviations: Ard: Ardenne (Namur and Dinant Synclinoria); Arm: Armorican Massif; Bhm: Bohemian Massif; Bln: Boulonnais; CcA: Carnic Alps; Ctz: Cantabrian Zone; Dvs: Devonshire; Grm: Germany (Eifel, Ruhr, Sauerland, Bergisches Land, Thuringia, Harz); IbC: Iberian Cordillera; Mth: Mouthoumet Massif; MtN: Montagne Noire; NMc: North Morocco (Doukkala, Meseta); OMZ: Ossa Morena Zone; Pld: Poland (Holy Cross Mountains, Pomerania); Ptd: Pontides; Rus: Russia (Volga and Urals areas; Baschkiria); Sao: Saoura; SMc: South Morocco (Anti-Atlas, Tafilalt); Tns: Tunisia; Trd: Taurides; Ygv: Ex-Yugoslavia (Serbia). For the reviewed literature on Givetian ostracods of those areas, see text. A. Faunal affinities between the Cantabrian Zone and other places in Europe and neighbouring areas during the Givetian; B. Middle Devonian palaeogeographic reconstruction (adapted from Blakey 2007).