Acratia pentagona Casier and Lethiers, 2002

Casier, Jean-Georges, Devleeschouwer, Xavier, Lethiers, Francis, Préat, Alain & Racki, Grzegorz, 2002, Ostracods and fore-reef sedimentology of the Frasnian-Famennian boundary beds in Kielce (Holy Cross Mountains, Poland), Acta Palaeontologica Polonica 47 (2), pp. 227-246 : 235-238

Acratia pentagona Casier and Lethiers , sp. nov.

Fig. 8C–F.

. Acratia sp. nov. C, aff. A. longa Zaspelova, 1959 ; Casier and Lethiers

2000: pl. 3: 8a, b.

Derivation of the name: From Greek pente gonia, five−angled. Allusion to the pentagonal outline of the carapace.

Holotype: Carapace. (Fig. 8C, D). PG21. IRScNB n° b3820. L = 0.44 mm; H = 0.22 mm; W = 0.22 mm.

Type locality: Psie Górki section at Kielce, Holy Cross Mountains of Poland.

Material.—17 carapaces.

Diagnosis.— Acratia pentagona sp. nov. differs from other species of the genus in elongate pentagonal outline with a long and straight dorsal border, in the posterior margin nearly straight and strongly inclined, and in the biconvex shape in dorsal view with a pinched anterior extremity.

Description.—In lateral view, elongate, mid−sized, preplete pentagonal carapace. Dorsal border long and straight. Ventral border slightly curved to straight. Anterodorsal margin moderately curved and anteroventral margin straight. Pointed anterior extremity at mid−height. Dorsal part of posterior margin nearly straight and strongly inclined. Posterior extremity with a backward−pointing spine on each valve, at ventral third of height. Maximum length at mid−height, and maximum height close to the anterior third of length. The left valve overreaches the right one all along the free margin, and the ventral overlap is slight. In dorsal view, biconvex−shaped with the anterior extremity slightly pinched. Maximum width at mid−length. Carapace surface smooth.

Remarks.— Acratia pentagona sp. nov. is most similar to Acratia longa Zaspelova, 1959 , from the Frasnian of the Russian Platform. But in this latter species the dorsal and ventral borders are not as long and straight, the posterior margin is less straight and inclined, and in dorsal view the carapace is less biconvex without a pinched anterior extremity.

Occurrence.—Frasnian (PG3, PG5, PG6, PG8?, PG16?, PG18, PG20, PG21, PG29) and Famennian (PG31) in the

Psie Górki section. Also in the Frasnian (KYA11, KYA39) of the Kostomłoty section.