Polyzygia symmetrica symmetrica Gürich, 1896

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 : 39-40

Polyzygia symmetrica symmetrica Gürich, 1896

(Pl. II: Figs. 28a & b)

1896 Polyzygia symmetrica nov. gen. nov. sp.; Gürich: 387–388, pl. 14, fig. 8–9. 1952 Polyzygia gürichi nov. sp.; Polenova: 77–78, pl. 2, fig. 5.

1953 Polyzygia symmetrica Gürich ; Přibyl: pl. 2, fig. 2–11.

1953 Polyzygia gürichi Polenova ; Krömmelbein: 53, pl. 3, fig. 1.

1953 Polyzygia geesensis nov. sp.; Krömmelbein: pl. 3, fig. 2.

1956 Polyzygia symmetrica Gürich ; Adamczak: 40–45, pl. 2, figs 1–8, pl. 3, figs. 1–7. 1963 Polyzygia symmetrica Gürich ; Le Fèvre: pl. 12, fig. 181, pl. 15, figs. 227–228. 1964 Polyzygia symmetrica Gürich ; Becker: 51–52, pl. 7, fig. 7.

1964 Polyzygia symmetrica Gürich ; Magne: pl. 16, fig. 20, pl. 30, fig. 281. 1969 Polyzygia symmetrica Gürich ; Groos: 21, pl. 4, fig. 9.

1971 Polyzygia symmetrica Gürich ; Adamczak: 140–141, pl. 1, figs. 3–6, pl. 2, figs. 8–9, pl. 3, figs. 1–2. 1971 Polyzygia symmetrica Gürich ; Le Fèvre: 823, 825, 829, pl. 5b, 6a, b. 1972 Polyzygia symmetrica Gürich ; Michel: 229–231, pl. 12, figs. 1–3. 1974 Polyzygia symmetrica Gürich ; Becker & Bless: 6, ann. 6.

? 1974 Polyzygia sp. 2; Blumenstengel: pl. 2, fig. 19.

1976 Polyzygia symmetrica Gürich ; Adamczak: ann. 11–12.

1982 Polyzygia symmetrica Gürich ; Becker & Groos-Uffenorde: 310, pl. 3, fig. 5, pl. 4, fig. 10. 1982 Polyzygia symmetrica Gürich ; Milhau: 22, pl. 5, fig. 134.

1983b Polyzygia symmetrica Gürich ; Milhau: 221, pl. 10, fig. 29.

1983 Polyzygia symmetrica Gürich ; Żbikowska: 51–52, pl. 13, figs. 1–2. 1985 Polyzygia symmetrica Gürich ; Coen: 19, pl. 6, fig. 1.

1985 Polyzygia symmetrica Gürich ; Casier: 836–837, pl. 1, fig. 10.

1985 Polyzygia cf. symmetrica Gürich ; Casier: pl. 1, fig. 9.

1985 Polyzygia symmetrica Gürich ; Lethiers et al.: 63, 65, pl. 8, fig. 8. 1988 Polyzygia symmetrica Gürich ; Becker: 409–411, pl. 2, fig. 24.

1988 Polyzygia symmetrica Gürich ; Milhau: 487, pl. 55, fig. 16.

1990 Polyzygia symmetrica Gürich ; Casier in Casier & Préat: pl. 1, fig. 31. 1993 Polyzygia symmetrica Gürich ; Malec & Racki: 376, text-fig. 11I. 1993 Polyzygia symmetrica Gürich ; Kasimi: pl. 17, fig. 13.

non 1995 Polyzygia symmetrica triebeli nov. subsp.; Becker, 129, text-figs. 2–3. 1995 Polyzygia symmetrica Gürich ; Casier in Casier et al.: 494, pl. 64, fig. 23. 1996 Polyzygia symmetrica Gürich ; Milhau: 74–75, pl. 2, fig. 1.

1996 Polyzygia symmetrica Gürich; Milhau: 76.

2001aPolyzygia symmetrica Gürich; Becker: 59–60.

2004 Polyzygia symmetrica Gürich ; Becker in Becker et al.: 46, pl. 4, fig. 6, pl. 9, figs. 6, 12–13. 2006 Polyzygia symmetrica Gürich ; Casier in Casier & Préat: pl. 3, fig. 1. 2006 Polyzygia sp. A, aff. symmetrica Gürich ; Casier in Casier & Préat: pl. 3, fig. 2. 2010a Polyzygia symmetrica Gürich ; Casier in Casier et al.: 41, pl. 3, fig. 8. 2011b Polyzygia symmetrica Gürich ; Casier in Casier et al.: pl. 3, fig. 8. 2013 Polyzygia symmetrica symmetrica Gürich ; Maillet: 113, pl. XIV, figs. 25–26, pl. XV, figs. 2a and b. 2013a Polyzygia symmetrica Gürich ; Maillet et al.: pl. 1, fig. 17.

cf. 2013b Polyzygia cf. symmetrica Gürich; Maillet et al.: 892.

2013 Polyzygia symmetrica Gürich ; Casier in Casier & Préat: 488, pl. IV, fig. 12.

Material. 4 specimens (1 C, 2 V, 1 F).

Diagnosis. Gürich (1896, p. 387) emend. Becker (1964, p. 52).

Description. Large, almost equivalve and quadrilobate carapace, sub-rectangular both in lateral and dorsal views, slender posteriorly. LV very slightly larger than RV. Hmax at 1/4 anterior; Lmax median; Wmax median. Straight dorsal margin. Almost straight ventral margin, oblique posteriorly. Ventral and dorsal margins converging posteriorly. Well rounded, regularly convex, anterior margin, forming an angle of about 130° with the dorsal margin. Posterior margin oblique, with the ventral part pointing anteriorly. Angles with dorsal (about 90°) and ventral (about 100°) margins are well rounded. Anterior part of the carapace higher than the posterior one. L1 and L4 joining ventrally and reaching the dorsal margin, thus forming a “W”-shaped ridge. In the mid-dorsal part of the carapace, L2 and L3 forming two distinct oval spots, with L3 reaching the dorsal margin. Marginal ridge along the free margins. Carapace flattened in-between this marginal ridge and the “W” ridge of the lobes (L1 and L4). Surface smooth.

Discussion. The specimens show a large carapace. This species is quite sparse in the Givetian of Asturias. Some morphological variation is observed, notably in the size and the flattening of the carina. The marginal part of the valves at free margins of the carapace can also be more or less large. L2 and L3 form two distinct oval spots, distinguishing the Candás Fm specimens from P. symmetrica triebeli Becker, 1995 .

Occurrences. Lower to Upper Givetian (Terres d’Haurs, Mont d’Haurs and Névremont Fms, and Fromelennes Fm, Fort Hulobiet Member), Ardenne (Flohimont, Cul d’Houille, Resteigne, Glageon, Mont d’Haurs and Aisemont sections), Eifelian to Middle Givetian (Chefar el Ahmar Fm), Saoura (Km 30 section), Givetian (Huergas Fm and Candás Fm, mb C), Asturias (Peran-Perlora and Huergas sections), Middle/Upper Givetian, Mouthoumet Massif (Berco Petito section); Givetian, Boulonnais and Morocco; Middle Devonian, Poland, Russia, Bohemia, Ruhr and Harz; Lower to Middle Devonian, Eifel.