Poloniella cf. claviformis ( Kummerow, 1953 )

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 : 26-27

Poloniella cf. claviformis ( Kummerow, 1953)

(Pl. II: Fig. 3 )

cf. 1953 Dizygopleura claviformis nov. sp.; Kummerow: 44, pl. 4, fig. 10.

cf. 1964 Poloniella claviformis (Kummerow) ; Becker: 76-77, pl. 13, fig. 8. 2013 Poloniella cf. claviformis (Kummerow) ; Maillet: 81, pl. X, fig. 5.

? 2013b Poloniella claviformis (Kummerow) ; Maillet et al.: fig. 7S.

cf. 2013 Poloniella claviformis (Kummerow) ; Casier in Casier & Préat: 488, pl. III, fig. 11.

Material. 5 specimens (4 C, 1 V).

Description. Medium-sized elongated and quadrilobate carapace, slender posteriorly. In lateral view, general outline of the valves suboval. The larger LV clearly overlaps the RV both antero-dorsally and ventrally, and slightly at the posterior end. Hmax at 2/5 anterior; Lmax at 1/3 dorsal; Wmax at 1/6 posterior. Straight dorsal margin, slightly oblique anteriorly in the RV. Straight hinge line reaching about 55% of Lmax. Antero-dorsal stragulum. Straight ventral margin. Ventral and dorsal margin almost parallel. Well rounded anterior margin, regularly convex. Anterior part of the valves flattened along the margin. Well rounded posterior margin, convex and sharper than the anterior one. Anterior part higher than the posterior one. L1 and L4 ventrally weakly connected. L2 and L3 joined by a large ventral connection. S1 and S3 ventrally connected. Mid-dorsal S2, pointing towards antero-ventral. L2, L3 and L4 describing an “S”-shape on each valve. Surface finely reticulated. A marginal ridge occurs along the free margin.

Discussion. Despite bad preservation, these specimens are close to Poloniella claviformis ( Kummerow, 1953) by exhibiting a quite rectangular outline, almost vertical lobes and S1 and S3, a clear ventral connection between S1 and S3, and a thick ventral connection between L2 and L3.

Occurrence. Middle Givetian (Candás Fm, mbs A, B and C), Asturias (Peran-Perlora section).

Figures

FIGURE 3. Stratigraphical distribution of ostracod taxa through the Candás Formation in the Peran-Perlora and Carranques sections. Samples numbers are replaced on a detailed stratigraphical column of the series, on which macro- and microfaunas’ occurrences are indicated.