Dnestrina Nikiforova and Modzalevskaya, 1968

Baliński, Andrzej, 2012, The brachiopod succession through the Silurian-Devonian boundary beds at Dnistrove, Podolia, Ukraine, Acta Palaeontologica Polonica 57 (4), pp. 897-924 : 920-921

Genus Dnestrina Nikiforova and Modzalevskaya, 1968

Type species: Dnestrina gutta Nikiforova and Modzalevskaya, 1968 ; Pridoli , Upper Silurian; Moldavia, Podolia .

Dnestrina gutta Nikiforova and Modzalevskaya, 1968 Fig. 19D–F, J .

1968 Dnestrina gutta sp. nov.; Nikiforova and Modzalevskaya 1968: 207–210; pl. 1: 1–14.

1968 Dnestrina gutta Nikif. et T. Modz. ; Modzalevskaya 1968: pl. 15: 15–19.

1982 Dnestrina gutta Nikiforova et Modzalevskaya, 1968 ; Modzalevskaya and Nikiforova 1982: 106, pl. 2: 8.

Material.—Two complete although compressed shells, and about 20 specimens embedded in sediment, mostly fragmentary. The present material was found 1.3–1.35 metres below the S–D boundary (beds −21 to −21.5).

Description.—Shell small, up to about 6.2 mm in length, subcircular to subovate in outline, slightly wider than long to subequal, widest slightly anteriorly to midlength, weakly concavo−convex; antero−lateral margins rounded, apical angle 110–120 °, hinge line short, almost straight, anterior commissure gently arched ventrally.

Ventral valve weakly convex, with almost imperceptible median carina; interarea flat, apsacline to nearly orthocline, up to 0.5 mm in height. Dorsal valve weakly concave, subcircular to slightly transversely elliptical, with poorly marked narrow, angular median sulcus originating near umbo.

Interior of the ventral valve with distinct subtriangular, elongated, bulbous median thickening, rising gradually in height and lanceolate anteriorly; valve margin forming distinct, flat and wide peripheral rim; mantle canals poorly impressed, radiating. Dorsal interior not preserved, but probably with crenulated dental sockets ( Fig. 19J ).

Shell surface smooth, but with distinct lamellose growth lines, usually 12–14 on adult specimens.

Remarks.—This characteristic form was originally described by Nikiforova and Modzalevskaya (1968) from the Dzvenyhorod Beds of the Skala Horizon of Moldavia and Podolia. The latter is confined to the vicinity of the Dnistrove village where the present material comes from. In the studied section the species occurs approximately in the same layers as Dayia bohemica , i.e., in the lowermost beds exposed in the trench and representing the uppermost Silurian ( Fig. 3 ).

Stratigraphic and geographic range.—The species is known from the the Dzvenyhorod Beds (uppermost Silurian) of Moldavia, Podolia, and Western Europe ( Alvarez and Copper 2002). Similar form was described as D. cf. gutta by Jahnke et al. (1989) from the uppermost Silurian of Yunnan Province of China.

http://dx.doi.org/10.4202/app.2011.0138

Figures

Fig. 19. Athyridide brachiopods from the Silurian–Devonian boundary beds at Dnistrove (Podolia, Ukraine). A–C. Dayia bohemica Bouček, 1941; three shells, ZPAL Bp. 56/200 (A), ZPAL Bp. 56/201 (B), and ZPAL Bp. 56/202 (C), in dorsal (A1, B1, C1), ventral (A2, B2, C2), lateral (A3, B3, C3), posterior (A4, B4, C4), and anterior (A5, B5, C5) views. D–F, J. Dnestrina gutta Nikiforova and Modzalevskaya, 1968. D, E. Two shells, ZPAL Bp. 56/208 (D) and ZPAL Bp. 56/209 (E), in dorsal (D1, E1), ventral (D2, E2), lateral (D3, E3), posterior (D4, E4), and anterior (D5, E5) views. F. Interior view of slightly damaged ventral valve, ZPAL Bp. 56/210. J. Shell ZPAL Bp. 56/207b in dorsal exterior view. G, H. Pseudoprotathyris infantilis (Kozłowski, 1929); two shells, ZPAL Bp. 56/176 (G) and ZPAL Bp. 56/177 (H), in dorsal (G1, H1), ventral (G2, H2), lateral (G3, H3), posterior (G4, H4), and anterior (G5, H5) views. I. Camarium sp.; shell ZPAL Bp. 56/29 in dorsal (I1), ventral (I2), lateral (I3), posterior (I4), and anterior (I5) views. Beds −24 (A–C), −21 (D–F, J), −4 (G, H), and 47–48 (I). Scale bars 2 mm.

Fig. 3. Distribution of brachiopod species and their frequency in the section at Dnistrove village. Secular pattern of δ13C (black curve) and δ18O (grey curve) values after Małkowski and Racki (2009) and Racki et al (2012). Lithology after Nikiforova et al. (1972: fig. 82).